Abstract: The complexity of surface topography can significantly influence the wettability, lubrication, and, in consequence, wear of materials in tribological contact. Therefore, wettability can be an important factor in contact lubrication. This research aims to find a correlation between a fractal, i.e., geometric, complexity of isotropic surfaces and the wettability at different observation scales. Surface wettability can be characterized under static and dynamic conditions by determining the dynamic contact angle hysteresis. Multiscale geometric correlations of topographic complexity and advancing, receding contact angle interactions are used to discover the best observation scales for strong correlation with dynamic surface lubrication. The analytical results confirmed that there is a certain range of scales in which the correlation coefficients between topographic complexity and dynamic wettability are strong (r > 0.9).

Keywords: Dynamic contact angle hysteresis | Fractal theory | Lubrication | Multiscale geometric analysis | Surface complexity | Wettability

Abstract: The study of complex systems involves understanding collective behaviors and global properties emerging from local interactions among multiple entities. This study presents a novel formulation of differential entropy specifically designed to analyze complex systems composed of a limited number of points. The method is applied to high-frequency spatial tracking data from football matches, enabling a detailed examination of player and ball configurations on the field. Various analytical configurations are explored, ranging from global team analysis to localized assessments centered on individual players or the ball, highlighting different aspects of spatial organization and interaction dynamics. The results demonstrate how differential entropy can effectively quantify spatial complexity and team compactness during a match. This framework offers significant potential for extension to other team sports, providing a robust and interpretable metric of spatial behavior. The proposed methodology establishes a solid basis for future research into the spatial-temporal dynamics of team sports.

Keywords: Complex Systems | Differential Entropy | Point Clouds | Spatial-Temporal Analysis | Team Sports Analytics

Abstract: Point cloud registration is a central theme in computer vision, with alignment algorithms continuously improving for greater robustness. Commonly used methods evaluate Euclidean distances between point clouds and minimize an objective function, such as Root Mean Square Error (RMSE). However, these approaches are most effective when the point clouds are well-prealigned and issues such as differences in density, noise, holes, and limited overlap can compromise the results. Traditional methods, such as Iterative Closest Point (ICP), require choosing one point cloud as fixed, since Euclidean distances lack commutativity. When only one point cloud has issues, adjustments can be made, but in real scenarios, both point clouds may be affected, often necessitating preprocessing. The authors introduce a novel differential entropy-based metric, designed to serve as the objective function within an optimization framework for fine rigid pairwise 3D point cloud registration, denoted as Iterative Differential Entropy Minimization (IDEM). This metric does not depend on the choice of a fixed point cloud and, during transformations, reveals a clear minimum corresponding to the best alignment. Multiple case studies are conducted, and the results are compared with those obtained using RMSE, Chamfer distance, and Hausdorff distance. The proposed metric proves effective even with density differences, noise, holes, and partial overlap, where RMSE does not always yield optimal alignment.

Keywords: density | entropy | holes | iterative closest point (ICP) | noise | partial overlap | Point cloud | registration | root mean square error (RMSE)

Abstract: Biofouling, the phenomenon involving the growth and accumulation of marine organisms on submerged surfaces, poses a significant challenge for the conservation of underwater structures and historical artifacts. Its presence can accelerate material degradation and complicate potential restoration efforts, especially in cases where direct recovery from the marine environment is not feasible. In this context, the early identification of biofouling is crucial for developing targeted intervention strategies and minimizing long-term damage. This study aims to lay the groundwork for creating a training dataset for a deep learning-based segmentation network. Images of submerged specimens were captured in both the visible spectrum and under UV illumination, which reveals biofouling often invisible to the naked eye. Using semi-automatic thresholding methods, segmentation masks were generated from UV images to approximate biofouling regions. RGB, HSV, Lab, and YCbCr color spaces were systematically compared to determine the most stable and reliable color model for segmentation. Results identified the HSV space as offering the most consistent thresholding performance across the dataset. These segmentation masks provide a foundation for training deep learning models aimed at automatically detecting biofouling in visible-light images, where manual annotation is challenging.

Keywords: Biofouling detection | Computer vision | Image segmentation | Underwater cultural heritage

Abstract: The aerospace industry increasingly relies on digital twins to estimate unmeasured quantities through Virtual Sensing techniques. In this context, this work presents the experimental validation of a computational fluid dynamics (CFD) model of an aluminum wing with a NACA 0018 profile. Wind tunnel measurements were collected at various flow conditions and compared against CFD simulations performed in Simcenter STAR-CCM+. The strong agreement, quantified through pressure distribution comparisons and Normalized Root Mean Square Error (NRMSE), confirms the reliability of the numerical model. Crucially, the validated CFD setup provides the basis for future implementation of Virtual Sensing schemes based on the Augmented Kalman Filter (AKF), enabling the estimation of aerodynamic pressure loads using limited sensor data. This validation step is thus essential to ensure the predictive quality of the digital twin in such Virtual Sensing frameworks for structural monitoring and control.

Keywords: Aerodynamics | CFD | Virtual Sensing | Wind tunnel

Abstract: Oscillating water column (OWC) devices are a promising technology for wave energy conversion, in which the efficiency of the power take-off (PTO) system plays a critical role. Savonius turbines are attractive candidates for OWC applications due to their mechanical simplicity, robustness, and inherent self-rectifying capability under bidirectional airflow; however, their aerodynamic performance is intrinsically limited. This work aims to enhance the performance of Savonius-based PTO systems through the aerodynamic optimization of external power augmenters. An experimental campaign was conducted on a scaled Savonius turbine operating under bidirectional, oscillatory airflow at two frequencies (0.1 and 1 Hz). A transient computational fluid dynamics (CFD) model based on a sliding mesh approach and dynamic fluid body interaction was developed and validated against experimental data. The numerical framework was then coupled with an optimization algorithm to refine the geometry of the power augmenters, with the objective of maximizing the turbine tip speed ratio. The optimized configuration showed a significant improvement in performance compared to both the bare turbine and the baseline power augmenter design. The maximum tip speed ratio increased by up to 52% at 1 Hz and 58.2% at 0.1 Hz, while the maximum power coefficient increased by up to 12.7%. Flow-field analysis revealed enhanced flow acceleration toward the driving scoop and reduced aerodynamic losses under both maximum and minimum thrust conditions. These results demonstrate the effectiveness of CFD-driven optimization for improving Savonius turbine PTO performance in OWC systems.

Abstract: Rheumatoid arthritis (RA) is a chronic systemic inflammatory disease that can cause severe joint damage and disability. The management of RA patients has evolved significantly over the past few decades due to improved detection of early disease progression and the initiation of targeted advanced treatments. However, several gaps remain, including disease risk assessment, early diagnosis, phenotypic identification, and risk of treatment failure. These gaps could potentially be addressed by the application of artificial intelligence (AI), defined as the ability of a machine to mimic intelligent human behavior, using machine learning and deep learning models. By analyzing various types of data, including clinical, laboratory, and imaging data, omics, demographics, and data from sensor applications or wearable technologies, it may be possible to improve the management of RA patients, as demonstrated by several studies. However, limitations related to interindividual variability, small datasets, study designs, and intrinsic model bias remain, making it difficult to generalize findings to larger cohorts of RA patients. The aim of this narrative review is to discuss the potential uses and limitations of AI-based algorithms in RA patients in light of the most recent scientific evidence.

Keywords: artificial intelligence | autoimmunity | deep learning | diagnosis | generative artificial intelligence | imaging | machine learning | predictivity | rheumatoid arthritis

Abstract: The Messina Strait Bridge is a bold and debated engineering project aimed at linking Sicily with Italy mainland across one of the Mediterranean’s most busy and strategic straits. An environmental comprehensive study has been conducted for estimating environmental costs associated with the bridge’s construction and suggesting management strategies for transportation phases to achieve environmental recovery. The findings serve as a foundation for future research to explore alternative scenarios based on evolving transportation systems and needs. The distinction between the bridge and its related works, such as access roads, railways, tunnels, and stations, is emphasized to provide specific environmental data, facilitating comparison with similar structures. The authors have conducted a Life Cycle Assessment of the bridge and its associated infrastructure, focusing on two critical phases: construction and use and maintenance. Details of the methods and of the data are reported to promote the reproducibility of the results and the definition of new scenarios by the scientific community. The model can also be easily exported to other straits around the world, even in different geographical and operational configurations.

Keywords: Life cycle assessment | Maritime navigation | Messina Strait Bridge | Sustainable infrastructure | Transportation systems

Abstract: Objectives: Accurate three-dimensional reconstruction of bone defects from cone-beam computed tomography (CBCT) datasets is a critical step in digital workflows for custom scaffold fabrication in guided bone regeneration (GBR). Although low-dose (LD) acquisition protocols are recommended to comply with ALARA (as low as reasonably achievable)/ALADA (as low as diagnostically acceptable) principles, concerns persist regarding their potential impact on STL geometric fidelity. Evidence comparing surface trueness across different CBCT acquisition protocols remains limited. This study aimed to evaluate and compare the dimensional accuracy of STL models derived from CBCT datasets acquired using six imaging protocols, including three LD and three standard-dose (SD) configurations, each tested at 0.150, 0.200, and 0.400 mm voxel resolutions. Methods: Standardized cortical bone defects were prepared on fresh porcine scapulae. A structured-light scanner was used to acquire high-resolution reference meshes. The specimen underwent six CBCT scans using predefined LD and SD settings. DICOM (digital imaging and communications in medicine) datasets were segmented with a standardized global threshold method and exported as STL files. Meshes were aligned to the reference model using iterative closest point (ICP) registration, and point-to-mesh deviation analysis was performed to assess surface trueness. Statistical comparisons were conducted using one-way ANOVA with Tukey’s post hoc test (p < 0.05). Results: All protocols demonstrated high overall accuracy, with more than 95% of surface points deviating less than ± 0.4 mm from the reference. The LD 0.400 mm protocol showed the highest conformity, with over 60% of surface points within ± 0.1 mm. High-definition (HD) protocols (0.150 mm) exhibited greater local deviations despite finer nominal resolution. Differences were more pronounced in cortico-cancellous transition areas. Conclusions: LD CBCT acquisition at 0.400 mm voxel size provides STL reconstructions with geometric fidelity comparable to or superior to higher-resolution settings, supporting its clinical use in scaffold-GBR while minimizing radiation exposure. Clinical Significance: This study demonstrates that LD CBCT protocols can provide STL reconstructions with sufficient geometric accuracy for clinical use in scaffold-GBR. These findings support safer imaging practices without compromising digital workflow reliability, aiding clinicians in balancing radiation exposure with the precision required for personalized surgical planning.

Keywords: bone regeneration | computer-aided design | computer-assisted | cone-beam computed tomography | image processing | radiation dosage

Abstract: Savonius turbines are widely used in energy recovery applications, including urban-integrated wind energy systems and Oscillating Water Column (OWC) setups for wave energy conversion. This study explores the use of a ducted Savonius turbine. Experimental tests were conducted on a scaled turbine to evaluate its performance. A Computational Fluid Dynamics (CFDs) model, incorporating Sliding Mesh and Dynamic Fluid Body Interaction (DFBI) techniques, was developed to replicate the experimental conditions. The accuracy of the model was confirmed through validation against experimental data. In total, four conditions were studied: one without a Power Augmenter, one with the Bell-Metha Power Augmenter, and two custom ones obtained by increasing the slope at the end of the Power Augmenters. To facilitate rapid turbine characterization, a fast computational method was developed, allowing the derivation of characteristic curves using only three CFD simulations per configuration. The reliability of this approach was assessed by comparing predictions with experimental results. Developing such a model is crucial, as it enables seamless integration with Reduced-Order Models (ROMs), significantly improving efficiency in evaluating multiple operating points.

Keywords: CFD | clean energy | Savonius | turbine

Abstract: owing tank tests are useful for evaluating the performance of hulls. One limitation of these tests is that large hulls cannot be tested at a 1:1 scale. However, although the tests are conducted on scaled models, the results can be scaled using ITTC (International Towing Tank Conference) procedures to provide a prediction of the full-scale model behaviour. Full-scale models, on the other hand, can be directly tested using CFD (Computational Fluid Dynamics) simulations, which do not have size limitations. In the present study, an ACS (Air Cavity Ship) hull model was tested in a 1:6 scale in a towing tank with and without air injection, with the full-scale results being derived from these tests. A towing tank scale and a full-scale CFD model were created in Simcenter Star-CCM +.

Keywords: ACS | CFD | Towing Tank

Abstract: No abstract available

Abstract: This study validates an innovative method using 3D facial scanning technology to analyze the depth of wrinkles and their potential correlation with cardiovascular risk factors. The research quantitatively assessed the severity of wrinkles in the forehead (HF), glabellar (GF), and periorbital (PO) regions, establishing a link between visible signs of aging and cardiovascular health risks. A trend was observed where greater wrinkle volume corresponds to higher cardiovascular risk scores, although the relationship was not uniformly linear, suggesting a complex interplay of factors influencing both cardiovascular health and aging.

Keywords: 3D Facial Scanning | 3D Model | Cardiovascular Risk | Deviation Analysis | Wrinkles

Abstract: This paper explores the influence of Voronoi tessellation parameters on the dynamic behavior of a mechanical tensioner's leaf spring used in internal combustion engines. By integrating Voronoi tessellation with Additive Manufacturing, the research investigates how varying the number of seeds affects the modal frequencies of the leaf spring. The study employs a design algorithm to maintain constant mass while adjusting the number of seeds and scaling factor, using a finite element (FE) formulation to predict and manage the leaf spring's dynamic nonlinear characteristics based on mass distribution. Modal simulations extract the natural frequencies, modal shapes, and participation factors of the component, analyzing how changes in these factors impact performance. The research findings underscore the significance of Voronoi parameters in modifying natural frequencies and dynamic behavior, highlighting their potential for topology optimization in frequency-sensitive applications. Validation comes through experimental testing, confirming the simulation results and emphasizing the role of appropriate mass distribution in controlling system frequencies.

Keywords: CAE Approach | Modal Frequencies | Participation Factors | Tensioner Leaf Spring | Topology Optimization

Abstract: The issue of resistance reduction through hull ventilation is of particular interest in contemporary research. This paper presents multiphase computational fluid dynamics (CFD) simulations with 2-DOF motion of a planing hull. The original hull was modified by introducing a step to allow air ventilation. Following an assessment of the hull performance, a simulation campaign in calm water was conducted to characterize the hull at various forward speeds and air insufflation rates for a defined single step geometry. Geometric analysis of the air layer thickness beneath the hull for each simulated condition was performed using a novel method for visualizing local air thickness. Additionally, two new parameters were introduced to understand the influence of spray rails on the air volume beneath the hull and to indicate the primary direction of ventilated air escape. A validation campaign and an assessment of uncertainty of the simulation has been conducted. The features offered by the CFD methodology include the evaluation of the air layer thickness as a function of hull velocity and injection flow rate and the air volume distribution beneath the hull. The air injection velocity can be adjusted across various operating conditions, thereby preventing performance or efficiency loss during navigation. Based on these findings, the study highlights the benefits of air insufflation in reducing hull resistance for high-speed planing vessels.

Keywords: Air cavity ships | Computational fluid dynamics | Hydrodynamics | Maritime sustainability | Planing hull

Abstract: This study examines the hydrodynamic behaviour of a 15-meter stepped planing hull through full-scale sea trials and numerical simulations. The sea trials, conducted in calm water conditions, provided key performance data, including pressure resistance, shear resistance and heave. A simplified procedure for conducting the sea trials was developed and implemented and these experimental results served as a baseline for a comparison with the results of a multiphase Computational Fluid Dynamics (CFD) model. This procedure enabled efficient testing while maintaining the accuracy of the results. The CFD simulation focused on understanding the natural ventilation process beneath the hull, a crucial factor in improving performance. Detailed studies were carried out on the wave profiles and resistance distribution under various flow conditions. The analysis explored the behaviour of natural ventilation in relation to resistance reduction, offering critical insights into optimizing hull performance through natural air flow mechanisms. This study underscores the potential of combining full-scale trials with advanced numerical modelling to enhance the design and performance evaluation of planing vessels. The findings contribute to the development of more efficient ships, with implications for improved energy efficiency and sustainability in recreational marine applications.

Keywords: Air Cavity Ships | CFD | Hydrodynamics | Sea Trials

Abstract: Maritime collisions represent one of the main risks for operational safety at sea and can involve various types of contact, such as ship-to-ship impacts, collisions with fixed obstacles (e.g., bridge piers) or groundings. Such events can cause severe structural damage to vessels and ships, compromising their integrity and leading to significant environmental consequences in the event of spills or transported cargo loss. This study is focused on the evaluation of the consequences of a collision event on a reference structure, assessing the energy absorbed, the deformation resulting from an impact and the damage extents and feature. An explicit dynamic finite element model is employed to simulate the temporal evolution of the impact event, with a focus on quantifying energy absorption, deformation patterns, and damage extent. The results offer valuable insights into the mechanics of hull breach formation and energy dissipation, supporting the development of crashworthy structural solutions and effective containment strategies. This is crucial for preventing oil dispersion in the event of a collision and for ensuring safe navigation to the nearest port. This study is conducted within the framework of the EMPATHY project (Enhanced Marine Pollution Emergency Actions to Preserve Ocean Health and the Safety of Ship and Navigation), funded by the National Recovery and Resilience Plan (NRRP), which aims to enhance preparedness and resilience in maritime safety by advancing the modeling of collision scenarios and guiding emergency response planning.

Keywords: crashworthiness | numerical models | Ship collisions

Abstract: In this article, the authors cited references 19–36 in contexts where they became redundant. While the authors acknowledge the value of these references, due to inappropriate locations they have repositioned the citations throughout the article to enhance clarity and coherence. Additionally, the authors have included a typographical error in Table 2 with the ‘Poisson ν’ and ‘Young's Modulus E [MPa]’ values for ‘Cancellous’ showing as switched. The authors have confirmed that the values ‘100’ and 0.2′ are to be switched. In the original article, the following statements were used to cite references 19–36 in Section ‘2.3 Simulation – mechanical properties, constraint system, contacts and methods’: “… The bone material of the vertebrae consists of two parts, cortical and cancellous. The mechanical properties have been modelled as a homogeneous and isotropic material [19,20,21,22,23,24,25,26,27,28]. There are different approaches in literature for modelling the cortical and cancellous structure, some authors use orthotropic models, however, in the scientific literature the simplification to isotropic material is widely used [29,30,31,32,33,34,35,26,36] …” The statements in Section ‘2.3 Simulation – mechanical properties, constraint system, contacts and methods’ is updated to include only references [20], [26], [29] and [30]. The updated statement should be as below: “… The bone material of the vertebrae consists of two parts, cortical and cancellous. The mechanical properties have been modelled as a homogeneous and isotropic material [20, 26]. There are different approaches in literature for modelling the cortical and cancellous structure, some authors use orthotropic models, however, in the scientific literature the simplification to isotropic material is widely used [29,30] …” The citation [19] has been moved to ‘Section 1. Introduction’. The original statement can be found below: “Unfortunately, a range of disorders and diseases can compromise the integrity and functioning of the spine, leading to pain, disability, and a reduced quality of life …” The correct version of the statement with citation [19] added should be as below: “Unfortunately, a range of disorders and diseases can compromise the integrity and functioning of the spine, leading to pain, disability, and a reduced quality of life [19] …” The citation [21] has been moved to Section ‘2.3 Simulation – mechanical properties, constraint system, contacts and methods’. The original statement can be found below: “… Four loading conditions were simulated, which involved a compressive force of a maximum value of 1000 N, to which was added, individually, a rotational load …” The correct version of the statement with citation [21] added should be as below: “… Four loading conditions were simulated, which involved a compressive force of a maximum value of 1000 N, to which was added, individually, a rotational load [21] …” The citation [22] has been moved to Section ‘1. Introduction’. The original statement can be found below: “… Age plays a pivotal role in the distribution of lesions …” The correct version of the statement with citation [22] added should be as below: Age plays a pivotal role in the distribution of lesions [22] …” The citation [23] has been moved to Section ‘2.3 Simulation – mechanical properties, constraint system, contacts and methods’. The original statement can be found below: “… The Poisson coefficient (Eq. (2.1)) will depend on two other coefficients, namely structural damping (Eq. (2.2)) and volumetric deformation (Eq. (2.3)) [40] …” The correct version of the statement with citation [23] added should be as below: “… The Poisson coefficient [23] (Eq. (2.1)) will depend on two other coefficients, namely structural damping (Eq. (2.2)) and volumetric deformation (Eq. (2.3)) [40] …” The citations [24] and [25] have been moved to Section ‘2.3 Simulation – mechanical properties, constraint system, contacts and methods’. The original statement can be found below: “… The authors were able to apply compressive loads up to over 1000 N without any sign of instability …” The correct version of the statement with citations [24] and [25] added should be as below: “… The authors were able to apply compressive loads up to over 1000 N without any sign of instability [24,25] …” The citation [27] has been moved to Section ‘1. Introduction’. The original statement can be found below: “… Over the years, research and clinical practice have led to the development of various treatment techniques aimed at restoring stability and proper functioning of the spine …” The correct version of the statement with citation [27] added should be as below: “… Over the years, research and clinical practice have led to the development of various treatment techniques aimed at restoring stability and proper functioning of the spine [27] …” The citation [28] has been moved to Section ‘2.1 Anatomy of the lower part of the spine and diseases’. The original statement can be found below: “… When the intervertebral disc deteriorates or ruptures, it can cause pain and dysfunction in the spine …” The correct version of the statement with citation [28] added should be as below: “… When the intervertebral disc deteriorates or ruptures, it can cause pain and dysfunction in the spine [28] …” The citation [31] has been moved to Section ‘4.3 Range of motion’. The original statement can be found below: “… Therefore, the simulation can be improved, e.g. by including the muscular apparatus …” The correct version of the statement with citation [31] added should be as below: “… Therefore, the simulation can be improved, e.g. by including the muscular apparatus [31] …” The citation [32] has been moved to Section ‘1. Introduction’. The original statement can be found below: “‥Among the various treatment approaches for spine stabilization, the Lateral Mass Screw (LMS) is an established method used for treating a wide range of spinal conditions …” The correct version of the statement with citation [32] added should be as below: “‥Among the various treatment approaches for spine stabilization, the Lateral Mass Screw (LMS) is an established method used for treating a wide range of spinal conditions [32] …” The citation [33] has been moved to Section ‘2.1 Anatomy of the lower part of the spine and diseases’. The original statement can be found below: “… Diseases that can affect the intervertebral disc include disc herniation, disc degeneration and spinal stenosis …” The correct version of the statement with citation [33] added should be as below: “… Diseases that can affect the intervertebral disc include disc herniation, disc degeneration and spinal stenosis [33] …” The citation [34] has been moved to Section ‘1. Introduction’. The original statement can be found below: “ …. These areas show the highest rates of degeneration, affirming the notion that these zones are particularly exposed to mechanical stresses and thus at greater risk …” The correct version of the statement with citation [34] added should be as below: “ …. These areas show the highest rates of degeneration, affirming the notion that these zones are particularly exposed to mechanical stresses and thus at greater risk [34] …” The citation [35] has been moved to Section ‘3.3 Range of motion’. The original statement can be found below: “… The Range of Motion (ROM) is a crucial aspect of spinal biomechanics, representing the relative range of motion between various pairs of vertebrae, in our case study these are L4-L5 and L5-S1 (Table 13) …” The correct version of the statement with citation [35] added should be as below: “… The Range of Motion (ROM) is a crucial aspect of spinal biomechanics, representing the relative range of motion between various pairs of vertebrae [35], in our case study these are L4-L5 and L5-S1 (Table 13) …” The citation [36] has been moved to Section ‘2.3 Simulation – mechanical properties, constraint system, contacts and methods’. The original statement can be found below: “… The elements were arranged in the anatomical direction given in the literature [41] (Table 4) …” The correct version of the statement with citation [36] added should be as below: “… The elements were arranged in the anatomical direction given in the literature [36, 41] (Table 4) …” The original version of Table 2 can be found below: [Table presented] The table has been updated so that the value of ‘100’ for ‘Poisson v’ of ‘Cancellous’ is switched with value ‘0.2’ for ‘Young's Modulus E [MPa]’ values of ‘Cancellous’ The correct version of the table should be as below: [Table presented] The references associated with the changes can be found below: [19] S.J. Atlas, R.A. Deyo, Evaluating and managing acute low back pain in the primary care setting, J. Gen. Intern. Med. 16 (2001) 120–131. [20] C.-S. Chen, C.-K. Cheng, C.-L. Liu, W.-H. Lo, Stress analysis of the disc adjacent to interbody fusion in lumbar spine, Med. Eng. Phys. 23 (2001) 485–493. [21] F. Heuer, H. Schmidt, L. Claes, H.-J. Wilke, A new laser scanning technique for imaging intervertebral disc displacement and its application to modelling nucleotomy, Clin. Biomech. 23 (2008) 260–269. [22] F. Heuer, H. Schmidt, Z. Klezl, L. Claes, H.-J. Wilke, Stepwise reduction of functional spinal structures increase range of motion and change lordosis angle, J. Biomech. 40 (2007) 271–280. [23] H.-M. Lin, Y.-N. Pan, C.-L. Liu, L.-Y. Huang, C.-H. Huang, C.-S. Chen, Biomechanical comparison of the K-ROD and Dynesys dynamic spinal fixator systems – a finite element analysis, Bio Med. Mater. Eng. 23 (2013) 495–505. [24] D.W. McMillan, D.S. McNally, G. Garbutt, M.A. Adams, Stress distributions inside intervertebral discs: the validity of experimental ‘stress profilometry, Proc. Inst. Mech. Eng. Part H J. Eng. Med. 210 (1996) 81–87. [25] A. Rohlmann, S. Neller, L. Claes, G. Bergmann, H.-J. Wilke, Influence of a follower load on intradiscal pressure and intersegmental rotation of the lumbar spine, Spine 26 (2001) E557–E561. [26] H. Schmidt, M. Bashkuev, M. Dreischarf, A. Rohlmann, G. Duda, H.-J. Wilke, A. Shirazi-Adl, Computational biomechanics of a lumbar motion segment in pure and combined shear loads, J. Biomech. 46 (2013) 2513–2521. [27] A.Y.L. Wong, G. Harada, R. Lee, S.D. Gandhi, A. Dziedzic, A. Espinoza-Orias, M. Parnianpour, P.K. Louie, B. Basques, H.S. An, D. Samartzis, Preoperative paraspinal neck muscle characteristics predict early onset adjacent segment degeneration in anterior cervical fusion patients: a machine-learning modelling analysis, J. Orthop. Res. 39 (2021) 1732–1744. [28] I. Yamamoto, M.M. Panjabi, T. Crisco, T. Oxland, Three-dimensional movements of the whole lumbar spine and lumbosacral joint, Spine 14 (1989) 1256–1260.] [29] A. Faizan, A. Kiapour, A.M. Kiapour, V.K. Goel, Biomechanical analysis of various footprints of transforaminal lumbar interbody fusion devices, J. Spinal Disord. Tech. 27 (2014) E118–E127. [30] V.K. Goel, A. Mehta, J. Jangra, A. Faizan, A. Kiapour, R.W. Hoy, A.R. Fauth, Anatomic facet replacement system (afrs) restoration of lumbar segment mechanics to intact: a finite element study and in vitro cadaver investigation, Int. J. Spine Surg. 1 (2007) 46–54. [31] Y. Guan, N. Yoganandan, J. Moore, F.A. Pintar, J. Zhang, D.J. Maiman, P. Laud, Moment–rotation responses of the human lumbosacral spinal column, J. Biomech. 40 (2007) 1975–1980. [32] A. Kiapour, D.G. Anderson, D.B. Spenciner, L. Ferrara, V.K. Goel, Kinematic effects of a pedicle-lengthening osteotomy for the treatment of lumbar spinal stenosis, J. Neurosurg. Spine 17 (2012) 314–320. [33] A. Nachemson, Lumbar intradiscal pressure: experimental studies on post-mortem material, Acta Orthop. Scand. 31 (1960) 1–104. [34] M.M. Panjabi, T.R. Oxland, I. Yamamoto, J.J. Crisco, Mechanical behavior of the human lumbar and lumbosacral spine as shown by three-dimensional loaddisplacement curves, J. Bone Jt. Surg. 76 (1994) 413–424. [35] M.J. Pearcy, Stereo radiography of lumbar spine motion, Acta Orthop. Scand. 56 (1985) 1–45. [36] Z.-C. Zhong, S.-H. Wei, J.-P. Wang, C.-K. Feng, C.-S. Chen, C. Yu, Finite element analysis of the lumbar spine with a new cage using a topology optimization method, Med. Eng. Phys. 28 (2006) 90–98.

Abstract: The quantitative assessment of the degree of order in a set of points is the subject of extensive investigation in discrete geometry. In this context, the Voronoi diagram finds applications across various fields, including medicine, biology, logistics, theoretical physics, and engineering. In the engineering domain, particularly in product design, the exploration of spatial order generates interest in the study and design of lattice structures or topological optimization. These specific applications contribute to enhancing certain characteristics of a structure or component, such as ergonomics, the quantity of material used, and mechanical properties. Delaunay triangulation, the dual of the Voronoi diagram, stands out as one of the most widely used algorithms for generating triangular meshes from point clouds. This work explores the analysis of primary entropic methods employed to evaluate the degree of order in Voronoi tessellation and Delaunay mesh. It Introduces an innovative approach centered on calculating the differential entropy of Voronoi seeds, which correspond to the vertices of Delaunay triangulation. The study shows the potential of the obtained results, both in terms of global and semi-local evaluations of the Delaunay mesh. It identifies novel usage scenarios within the context of product design. The results are thoroughly discussed and compared with other commonly utilized methodologies.

Keywords: Delaunay triangulation | Differential entropy | Mesh quality | Point clouds | Voronoi tessellation

Abstract: Oscillating Water Column (OWC) devices are a promising technology for harnessing wave energy, utilizing the movement of seawater induced by waves. OWC systems offer renewable energy solutions with minimal environmental impact. The Power Take-Off (PTO) system, crucial for converting pneumatic power into usable energy like electricity, is central to their functionality. This study investigates using a ducted Savonius turbine as the PTO system in an OWC setup. Experimental tests were conducted on a scaled Savonius turbine to assess the turbine efficiency. A CAD model of the setup was created and imported into a Computational Fluid Dynamics (CFD) environment for detailed fluid dynamic analysis, utilizing the Sliding Mesh combined with the Dynamic Fluid Body Interaction (DFBI) technique to simulate turbine motion. Validation of the CFD model was achieved by comparing numerical results with experimental data. A fifth-order Bell-Metha polynomial profile power augmenter was considered to enhance turbine performance by increasing the rotational speed and reducing resistance. This strategy aims to minimize energy loss and operational disturbances by targeting vortex reduction upstream of the turbine. With the validated setup, power augmenters were introduced and a parametric analysis was performed to assess turbine efficiency, using the coefficients of the Bell-Metha profile as parameters. The results were promising for future development in wave energy conversion technology.

Keywords: CFD | OWC | Parametric analysis | Savonius turbine

Abstract: This study investigates the impact of Voronoi tessellation parameters on the dynamic behaviour of a leaf spring employed in a tensioner for internal combustion engine timing systems. The research utilizes a custom-developed algorithm to apply Voronoi tessellation while maintaining a constant mass by varying the number of seeds and scaling factors. Modal simulations were carried out to determine the natural frequencies, participation factors, and mode shapes of the component. These simulations were validated through experimental tests performed using a hammer impact test, which provided reliable and detailed measurements of the system’s dynamic response under different loading conditions. The experimental results revealed a strong correlation with the simulated data, demonstrating the accuracy of the proposed methodology. By modifying Voronoi tessellation parameters, it was possible to control and predict changes in natural frequencies and participation factors. These findings underscore the potential of Voronoi tessellation in dynamic system optimisation, enabling the design of components with tailored properties for improved performance. This research opens new avenues for integrating Voronoi-based design approaches with topology optimisation, particularly in the frequency domain, paving the way for innovative applications in mechanical and structural engineering.

Keywords: CAE approach | Modal frequencies | Optimal mass distribution | Participation factors | Tensioner leaf spring | Topology optimisation | Word

Abstract: The desire to improve the safety of navigation, especially in restricted and very busy areas like the straits, leads researchers to evaluate possible uses of Artificial Intelligence as an alternative to the traditional probabilistic methods. This is possible thanks to the large amount of available AIS data generated by ships in transit. In this work, a Machine Learning algorithm (Classification Decision Tree) was trained with eight features coming from AIS data of the Strait of Messina (Italy), with the aim of carrying out a two-class classification of the single AIS data to find anomalies in ship transits that could compromise navigation safety. Since anomalous events are relatively rare, compared to the large amount of information related to the normal navigation situations, the challenge of this work was to obtain an artificial dataset with the aim of simulating the possible anomalous navigation conditions for the Strait investigated, known the active risk mitigation means one. For this reason, the dataset containing abnormal events was obtained simulating different risk scenarios. A hyperparameters tuning with a Bayesian optimization approach and a 5-fold cross validation have been performed to improve the quality of the model and a large dataset has been tested. The accuracy of both validation and test phases is <99.5% and <95.9%, respectively. This can make it possible to identify anomalous navigation conditions in real time, in order to quickly classify possible conditions of risk. The method can be used as a Decision Support Tool by the authority in order to improve the capacity of the single operator to identify the possible risk situation inside the Strait of Messina.

Keywords: AIS data | decision support tool | machine learning | navigation | real time monitoring | risk minimization

Abstract: In motorsport applications the adoption of a Computational Fluid Dynamics (CFD) simulation is a well-established practice. This analysis is very useful to understand and optimize the aerodynamics performance of the prototypes. By means of specific algorithms it’s possible to define one or more control parameters and so changing the geometry of the fairing to optimize an engineering value. These algorithms are largely used in other fields such as the hydrodynamics one but they are not largely used in motorsport, especially in motorcycles. The motorcycle considered in this study is a prototype participating in the Moto2 World Championship, the middle class of the MotoGP World Championship. Starting from tests, carried out in the wind tunnel, a baseline model was firstly created to get a correlation between experimental and numerical results and so used for a subsequent process of shape optimization. With the main objective of reducing the overall drag, a set of control points was defined on the existing geometry to deform the surface of the front fairing. These points have been used by the optimization algorithm to find the shape that reduces the overall drag. The optimized geometry made it possible to obtain the desired drag reduction.

Keywords: Aerodynamics | CAE | CFD | Motorsport | Shape Optimization

Abstract: This review explores a variety of techniques that utilize air injections beneath a vessel’s hull to reduce drag and consequently improve energy efficiency. It focuses on the methodologies of microbubble drag reduction (MBDR), air layer drag reduction (ALDR), and air cavity drag reduction (ACDR), offering insights into their design, operational mechanisms, and potential applications. This review provides a detailed examination of the underlying principles of these technologies, incorporating a blend of experimental research, numerical simulations, and mathematical modelling to offer a comprehensive understanding. It references recent experimental data, highlighting how these findings corroborate with numerical simulations and are further explained through mathematical models. Conclusively, this review accentuates the transformative influence of air injection methods in drag reduction within the maritime industry, emphasizing their pivotal role in boosting operational efficiency, reducing environmental impact, and driving the evolution of naval design and transportation. Through a balanced and detailed analysis, this review provides a holistic view of the current state and future prospects of these innovative resistance reduction strategies.

Keywords: air cavity | air layer | air lubrication | CFD | drag reduction | microbubble | sustainability

Abstract: Oscillating Water Column (OWC) systems harness wave energy using a partially submerged chamber with an underwater opening. The Savonius turbine, a vertical-axis wind turbine, is well-suited for this purpose due to its efficiency at low speeds and self-starting capability, making it an ideal power take-off (PTO) mechanism in OWC systems. This study tested an OWC device with a Savonius turbine in an air duct to evaluate its performance under varying flow directions and loads. An innovative aspect was assessing the influence of power augmenters (PAs) positioned upstream and downstream of the turbine. The experimental setup included load cells, Pitot tubes, differential pressure sensors and rotational speed sensors. Data obtained were used to calculate pressure differentials across the turbine and torque. The primary goal of using PA is to increase the CP–λ curve area without modifying the turbine geometry, potentially enabling interventions on existing turbines without rotor dismantling. Additionally, another novelty is the implementation of a regression Machine-Learning algorithm based on decision trees to analyze the influence of various features on predicting pressure differences, thereby broadening the scope for further testing beyond physical experimentation.

Keywords: machine learning | OWC | predictive model | Savonius

Abstract: The vertebral column represents an essential element for support, mobility, and the protection of the central nervous system. Various pathologies can compromise these vital functions, leading to pain and a decrease in the quality of life. Within the scope of this study, a novel redesign of the Intersomatic Cage, traditionally used in the presence of discopathy, was proposed. The adoption of additive manufacturing technology allowed for the creation of highly complex geometries, focusing on the lumbosacral tract, particularly on the L4-L5 and L5-S1 intervertebral discs. In addition to the tensile analysis carried out using Finite Element Analysis (FEA) in static simulations, a parallel study on the range of motion (ROM) of the aforementioned vertebral pairs was conducted. The ROM represents the relative movement range between various vertebral pairs. The introduction of the intersomatic cage between the vertebrae, replacing the pulpy nucleus of the intervertebral disc, could influence the ROM, thus having significant clinical implications. For the analysis, the ligaments were modelled using a 1D approach. Their constraint reaction and deformability upon load application were analysed to better understand the potential biomechanical implications arising from the adoption of the cages. During the FEA simulations, two types of cages were analysed: LLIF for L4-L5 and ALIF for L5-S1, subjecting them to four different loading conditions. The results indicate that the stresses exhibited by cages with a NET structure are generally lower compared to those of traditional cages. This stress reduction in cages with NET structure suggests a more optimal load distribution, but it is essential to assess potential repercussions on the surrounding bone structure.

Keywords: Biomedical computer aided design | CAE method | Magnetic resonance imaging | Range of motion

Abstract: For the more than 100 years forensic firearm identification has been conducted by examining physical evidence under the optical comparison microscope. Nowadays, 3D technology offers advanced and powerful tools that deserve to be considered to evaluate a new and different solution for processing ballistic data. The method proposed in this work is based on the processing of the 3D point clouds of the cartridge case back. It starts with the transformation of the point clouds of the bottom of the cartridge case into a 64-bit greyscale image. The second step is to use a polar derivation technique for exploiting the polar characteristics of the features impressed on the cartridge and also to overcome the problem of the initial orientation of the cartridge. The dataset used for the experimental part was made by Messina Carabinieri Scientific Investigation Department (Italy) and it contains point clouds of several cartridge cases acquired with an Automated Ballistic Identification System (ABIS). After the pre-processing, the method has been tested with SIFT to verify the invariance on the feature extracted. Although not yet ready for forensic applications, the method appears to be promising and innovative to be applied in the common pattern recognition process in this field.

Keywords: Ballistics | Cartridge Cases | Firearm Identification | Forensics | Point Clouds

Abstract: Many workers and citizens have been forced to make a lifestyle change in the past two years due to the pandemic emergency. In order to keep a high level of personal health, the doctors suggest to do fitness exercises. Before the pandemic it was possible to do these exercises at the gym or during dedicated session in the office supervised by professional trainers. During the pandemic emergency the gyms were closed, the workers were forced to stay home and the people started to do gym exercises by themselves without the control of a professional figure. This situation could lead to several diseases associated to musculoskeletal disorders if the exercises are performed incorrectly. In this work, an approach based on the pose-estimator application OpenPose is developed. The reference exercise is an isometric squat performed by a professional trainer. During the exercise, thanks to a deep neural network, the pose-estimator gets a series of key-points and vectors which represent the user’s pose. A dataset of videos (for both the correct and incorrect postures) has been used to train several machine learning algorithms. The result is an automatic tool that recognizes incorrect poses during the exercise and helps the performer to correct it.

Keywords: Computer vision | Ergonomics | Machine learning | Physiotherapy | Posture assessment

Abstract: The use of arthroprosthetic devices for spinal stabilization is a widely used procedure in the field of biomechanics. There are several problems on the spinal columns that need to use devices like cages to keep distance between the vertebrae. In many cases, these devices are implanted between the vertebrae to keep a clearance between them and so avoid pain or numbness of the limbs. Thanks to new manufacturing approach, it is possible to use powerful topological optimization algorithms to get biomedical devices with high values of performance. Aim of the paper is to define a simulation to get the kinematic behavior of the human cervical structure. Thanks to the results of the simulation, the model can be used to study the effectiveness of an arthroprosthetic device positioned to stabilize the cervical segment of the spinal column and improve the rehabilitation process. The part of the vertebral column under examination is between C3 and C7. Computer Aided Design has been used starting from the 3D scan of the cervical spine obtained by magnetic resonance imaging. The great potentiality of the method is to use a kinematic simulation that models the vertebrae as rigid body and the ligaments and intervertebral discs as a system of springs. This allows to reduce the cost of simulation in term of complexity and time to reach the solution. The kinematic mechanism will be used in a second step for the assessment of the insertion of arthroprosthetic device in terms of stabilization of the upper part of the spinal column. The main objective is to have a tool that allows to immediately identify the best geometry for the patient and to optimize the shape for each specific case. The tool will be tested in future in order to verify the robustness and reliability in several other cases.

Keywords: Customization of Medical Devices | Kinematics | Magnetic Resonance Imaging | Range of Motion | Simulation

Abstract: Aim of all designers is to optimize the product principally in term of mass. The classic manufacturing processes constraint the designer to use a limited number of parameters for obtaining the best results. New manufacturing processes like Additive Manufacturing, open the way to a new optimization strategies, one of the most important is the topology optimization. The objective function is to reduce the mass keeping other functionalities of the product intact. The starting geometry of each topology optimization can be the geometry used for the classic manufacturing method or it can be the lattice structure or a geometry with a tessellation applied by means Voronoi technique. Aim of this paper is to investigate the potential of Voronoi tessellation in the field of structural engineering. A titanium plate with Voronoi tessellation is modelled varying the number of seeds and keeping the total mass unaltered. Thanks to a finite element simulation, for each condition a modal analysis has been performed and the natural frequencies have been extracted. The paper discusses about the influence of the number of seeds to the natural frequencies of plate. This could be a new way and a starting point for topology optimization oriented to the management of natural frequency domain exploiting the Voronoi parameters.

Keywords: CAE approach | Design for additive manufacturing | Topology optimization

Abstract: Ergonomics focuses on the analysis of the interaction between human beings and their working environment. During the riding of a motorbike, ergonomics studies the rider’s posture on the motorbike. An incorrect posture can lead to physical and psychological discomfort, and can affect the perception of risk and the handling of the motorcycle. It is important for motorcyclists to adopt a good riding posture, for their health and road safety. The aim of this work is to propose a fast, cheap, and sufficiently robust method for the 3D reconstruction of the posture assumed by a motorcyclist. The stereo vision and the application of OpenPose made it possible to obtain a 3D reconstruction of the key points, and their evolution over time. The evaluation of the distances between the 3D key points, which represent the length of the various parts of the body, appears to remain sufficiently stable over time, and faithful to the real distances, as taken on the motorcyclist themself. The 3D reconstruction obtained can be applied in different fields: ergonomics, motorsport training, dynamics, and fluid dynamics analysis.

Keywords: 3D human posture | computer vision | digital twin | ergonomics | motorsport | OpenPose | posture assessment

Abstract: Our cultural society has made remarkable advancements in creating digital models that depict the built environment, landscape, and reality. The advent of technologies such as terrestrial laser scanning and drone-based photogrammetry, coupled with sophisticated software capable of processing hundreds of photographs to generate point clouds, has elevated the significance of three-dimensional surveying in documentation and restoration. Point cloud processing and modeling software enable the creation of precise digital replicas of the investigated architecture, which can be scaled down and transformed into physically identical models. Through the export of STL files and the utilization of both subtractive and additive 3D printing technologies, tactile models resembling traditional manually crafted plastics can be obtained. An exemplary study focuses on the Gothic church of Santa Maria Alemanna in Messina, Italy, where laser scanner surveys and 3D prints using various technologies were applied to different parts of the building. The models were produced using a CNC milling machine and a 3D printer for fused deposition modeling. The sustainability of these production technologies was assessed through a Life Cycle Assessment, demonstrating the environmental advantages of additive manufacturing, including the use of materials with high recyclability and lower energy consumption. Additionally, the additive approach helps reduce processing waste.

Keywords: 3D printing | architecture recovery | cultural heritage | digital models | Life Cycle Assessment

Abstract: This article introduces the Differential Entropy-based Compactness Index (DECI), a new metric for synthetically describing the spatial distribution of point clouds. DECI is founded on the differential entropy (DE) of point clouds, and if they depict a moving object distribution, the index enables real-time monitoring. Historical data analysis allows for the study of DECI trends and average values in defined intervals. Multiple practical applications are suggested, including risk assessment, congestion measurement, traffic control (including autonomous systems), infrastructure planning, crowd density, and health analysis. DECI’s real-time and historical insights are valuable for decision-making and system optimization and hold potential as a feature in machine learning applications.

Keywords: 3D geometry distribution assessment | compactness index | differential entropy | point clouds | real-time | risk assessment

Abstract: To contrast the naval emissions in terms of Sulphur and Nitroxides, recently, the institution of Emission Control Areas has increasingly prompted shipowners to choose new-generation engines capable of using Liquified Natural Gas as a marine fuel. This study presents a comparative Life Cycle Assessment, cradle-to-grave, between two different engines on a cruise ferry. One is a traditional Diesel machinery system and the other is a Liquified Natural Gas one. The two configurations have been analysed within 17 different impact categories in terms of climate change, human health, resourced depletion and ecosystems. The studied phases of the ship's life were the building, operation and dismantling. The results showed and quantified the environmental differences deriving from the use of Liquified Natural Gas in all the phases of the life of the ship. Generally, the LNG propulsion has shown to be more environmentally performing, but, particularly interesting are the results in terms of climate change, influenced by lower CO2 emissions but also by the phenomenon of methane slip that can increase the CO2-equivalent effect. The energy costs of transport and liquefaction of gas also have an impact to consider. Analyses of uncertainty on the data and of sensitivity on fuel consumptions and losing of steel during the shipbuilding were carried out.

Keywords: Climate change | Green design | Life Cycle Assessment | Liquified Natural Gas | Shipbuilding

Abstract: The use of ventilated hulls is rapidly expanding. However, experimental and numerical analyses are still very limited, particularly for high-speed vessels and for stepped planing hulls. In this work, the authors present a comparison between towing tank tests and CFD analyses carried out on a single-stepped planing hull provided with forced ventilation on the bottom. The boat has identical geometries to those presented by the authors in other works, but with the addition of longitudinal rails. In particular, the study addresses the effect of the rails on the bottom of the hull, in terms of drag, and the wetted surface assessment. The computational methodology is based on URANS equation with multiphase models for high-resolution interface capture between air and water. The tests have been performed varying seven velocities and six airflow rates and the no-air injection condition. Compared to flat-bottomed hulls, a higher incidence of numerical ventilation and air–water mixing effects was observed. At the same time, no major differences were noted in terms of the ability to drag the flow aft at low speeds. Results in terms of drag reduction, wetted surface, and its shape are discussed.

Keywords: Air cavity ships | Computational fluid dynamics | Hull design | Hull ventilation | Stepped planing hull

Abstract: Rigid inflatable boats (RIBs) are a well-known typology of inflatable crafts, largely used as rescue and pleasure aims thanks to the high performance in terms of stability and loading surface. They are a hybrid boat with inflatable tubulars, like a dinghy, and rigid keel, like a traditional planing hull. This paper analyses the planing performance of a novel, patented, RIB model, that has the peculiarity to have tubulars that do not go uninterruptedly from bow to stern but only for about half the length. In this way it is possible to reduce the wetted surface and to channel the air under the hull, allowing a good ventilation. A wide computational fluid dynamics analysis allowed the authors to study the hydrodynamic behaviour of the boat and to discuss the results.

Keywords: Computational fluid dynamics | Computer aided engineering | Planing hull | Rigid inflatable boats

Abstract: The designers of two-wheeled motorcycles, in the phase of setting up a new project, have the need to carry out ergonomic evaluations on both the pilot and the passenger, from which the optimal comfort and control conditions will arise during the future use of the vehicle. Commonly, the most used method is based on the previous experience of the manufacturer and on the comparison with the choices made by the competitors. This article describes a methodology developed in collaboration with the Italian motorcycle brand Aprilia, owned by Piaggio &amp; C., a company world leader in the sector, designed for the setup phase of new vehicles. The method provides a flexible tool, starting from the Enduro segment and for the different users’ body size (expressed in percentiles). The analysis was done on five commercial Enduro motorcycles from different leading competitor manufacturers. The authors used a mixed method based on numerical and experimental data, detected on virtual models, and on report cards made by professional testers. The results have been showed and discussed.

Keywords: Anthropometric | CAE | Ergonomics | Human factors | Motorcycles

Abstract: The spreading of high computational resources at very low costs led, over the years, to develop new numerical approaches to simulate the fluid surrounding a sail and to investigate the fluid–structure interaction. Most methods have concentrated on upwind sails, due to the difficulty of implementing downwind sailing configurations that present, usually, the problem of massive flow separation and large displacements of the sail under wind load. For these reasons, the problem of simulating the fluid–structure interaction (FSI) on downwind sails is still subject of intensive investigation. In this paper, a new weak coupled procedure between a RANS solver and a FEM one has been implemented to study the FSI problem in downwind sailing configurations. The proposed approach is based on the progressive increasing of the wind velocity until reaching the design speed. In this way, the structural load is also applied progressively, therefore, overcoming typical convergence difficulties due to the non-linearity of the problem. Simulations have been performed on an all-purpose fractional gennaker. The new proposed method has been also compared with a classic weak FSI approach. Comparable results have been obtained in terms of flying shape of the gennaker and fluid-dynamic loads. The most significant characteristic of the proposed procedure is the easiness to find a solution in a very robust way without convergence problem, and also the capability to reduce the simulation time with regard to the computational cost.

Keywords: Computational fluid dynamics | Finite element method | Fluid–structure interaction | Gennaker | Interactive sail design | Mainsail

Abstract: During tillage, soil engaging tools are exposed to very critical working conditions due to soil friction. This produces an abrasive wear which needs to be monitored in order to avoid high costs for machine maintenance and fuel consumption and a deterioration of tillage quality. A commonly used method for wear diagnosis is the evaluation of the mass loss and volume change after a prolonged component usage. The instruments generally used for the assessment of these two quantities give only general and punctual information about the wear. Modern three-dimensional scanning technologies allow for creating a numerical model of the worn component and thereby extracting knowledge of the wear pattern. In this paper, the wear pattern of four ploughshares of a semi-mounted plough were analysed and compared. Each ploughshare was scanned by means of a structured blue-light 3D scanner before and after a prolonged field usage. From the scans, the cutting edge profile, described with three parameters, and the blade profile were calculated. The wear pattern and the volume losses were numerically calculated through Hausdorff's method and deviation analysis. Results of the experiments showed that cutting edge profile parameter of ploughshares could differ significantly from each other. Moreover, even if the wear pattern was very similar in shape for all the ploughshares, a large variability in volume losses was observed between the ploughshares. The adopted methodology permits to easily evaluate the wear pattern of tillage tools.

Keywords: 3D scanning | Abrasive wear | Blade profile | Cutting edge | Ploughshares

Abstract: In the speed-based competition, with the use of fast vehicles, a fundamental aspect is the safety and comfort of the drivers. In each speed-based competition, the drivers are subjected to vibrations and stresses whose evaluation is fundamental in order to quantify the discomfort of them. The comfort conditions are guaranteed by a deep study of the correct size of the internal spaces, the right posture of the drivers and the right choice of the position of the elements inside the vehicles (damping elements, position of the steering wheel, position of instruments, etc.). Another important aspect is the assessment of the escape spaces in case of accident. To reach these goals, the Governing Body act with the definition and the verification of technical rules. In this work the field of interest is powerboats sport. During the powerboat race, the reached speed and the z-acceleration of the boat lead to several stresses on drivers. Two different approaches have been investigated, a traditional 2D approach and an innovative 3D approach. Results have been discussed.

Keywords: Ergonomics | Human factors | Safety design | Seat comfort

Abstract: Topological optimization is a fairly innovative numerical technique that makes it possible to reduce the mass of mechanical components. It is an alternative to the optimizations of shape or geometry that allow to highly improve the efficiency of products. The recent development of metal additive manufacturing technologies allows the production of pieces that were not feasible before, permitting the use of topological optimization in many fields. In the biomedical field, for example, the reduction of prosthetic and orthotic materials allows to save weight, to the advantage of comfort, and to minimize the invasiveness of these systems. In this paper, an optimization of a system consisting of a femoral nail and two screws is carried out. The pieces were obtained by 3D scanning of prostheses, so as to obtain the true geometry. The femur is the standard one in literature. Following topological optimization, a new nail, with a mass of 60% of the previous one, was obtained, without limiting the functionality or the reliability of the product. Results and methodological problems are discussed.

Keywords: Additive manufacturing | Biomedical engineering | Femoral nail | Reverse engineering | Topology optimization

Abstract: The use of composite materials allows to have a great flexibility in terms of mechanical and physical characteristics. One of the most used composite structure in naval field, is the sandwich, which is composed by a stacking sequence of different plies. The designer, in preliminary phase, must handle a great quantity of degree of freedom (types of materials, orientation of the fibres, position along the stack, thickness, etc.) in order to reach the best compromise between mechanical behaviour, environmental impacts and production costs. Finite Element analysis represents a useful tool in order to optimize all these parameters and to estimate the outcome of experimental tests at design stage. The main goal of this work is to develop and to validate a FE model for the simulation of a particular family of composites, widely used in naval field and, in particular, in High Speed Crafts and powerboats. The first part of the paper concerns the experimental tests on two different types of sandwich specimens. Two families of tests were conducted: four-point bending tests and impact drop tests. The second part of the paper focuses on the validation of a FE model for both experimental setups.

Keywords: Finite Element | Impact tests | Lightweight composites | Offshore powerboats | Sandwich composites

Abstract: One of the most important aspects, in the ACS and multi stepped hull design, is the choice of the geometrical shape of the cavity and the steps. In this article a complete experimental and numerical campaign on a multi stepped ACS has been carried out, varying the velocity and the air flow rate under the hull. The experimental tests have been conducted in an ITTC Towing Tank allowing to validate the numerical simulations obtained by means of a CFD U-RANSe (Unesteady Reynolds Averaged Navier-Stokes equations) code. The CFD setup is described in detail. From this campaign a critical analysis of the Froude number influence on the air cushion shape has been argued. The authors identified four different behaviours, from low to very high Froude numbers. The use of CFD has allowed to observe quantities of difficult evaluation by means of traditional experimental test, as e.g. the frictional component of the resistance, the airflow path lines and the volume of fraction in transversal and longitudinal sections. The results have been discussed.

Keywords: Air Cavity Ships | Computational Fluid Dynamics | Hull Design | Multi stepped hull | Ship Resistance | Towing tank tests

Abstract: In the world of powerboats competition, the high-performance sandwich-structured composites have completely replaced traditional materials. During the competition, the structure of this kind of ships is subjected to repeated impacts. It is then fundamental to understand the damage evolution in order to select the most appropriate materials and increase safety issues. The present study is aimed at analysing the behaviour of sandwich-structured composites undergoing repeated low-energy impacts. Three different materials have been analysed. Two are sandwich-structured composites used for the cockpit of offshore powerboats and differing only by the core cell thickness. The third material is composed only by the skin of the same sandwich structures, without the core. Impacts were made at three different energy levels: 15, 17.5 and 20 J. In addition to the parameters typically used for the assessment of the impact damage, a new damage assessment has been carried out by means of three-dimensional optical measurements of the imprinted volumes resulting from the impact events. This approach has allowed the definition of a correlation between the imprinted volumes and the number of impacts, until the complete perforation, for each single specimen. Finally, thanks to usual indexes and the imprinted volumes, some considerations are developed about the influence of the core cell thickness in powerboats design.

Keywords: damage accumulation | lightweight composites | offshore powerboats | optical measurements | Repeated impacts | safety design

Abstract: In recent years, a great world issue is the respect for the environment. Each researcher, in his competence field, proposes new technologies and new approaches in order to reduce the environmental impact of a product or of an industrial process. In the naval field, the main way in order to reduce the environmental impact of the ship during the navigation is the reduction of the drag resistance and so the reduction of requested power. There are many ways in order to obtain a reduction of drag. This paper investigates, with a preliminary numerical study by means of Computational Fluid Dynamics (CFD), the Air Cavity Ships technology (ACS). A first part of the paper concerns the study of the rising bubble phenomenon inside a water column, in order to choice the better solver settings and understand if the CFD is suitable for this kind of problem. In this phase the main parameters analyzed are: the air critical mass, the rising velocity, the shape and the air circulation inside the bubble. In the second part of the work, a flat plate model with artificial air injection is conducted in order to understand the possible advantages of this application. The principal impacts of this technology are presented in terms of drag coefficient and lift coefficient respect to trim and velocity coefficient. The CFD method could be a suitable and fast method, in the preliminary phase, for the design of the ACS.

Keywords: Air Cavity Ship | Artificial ventilation | CFD | Green design | Planing hull design

Abstract: The needs to reduce the frictional component of the resistance of a ship leads researchers to find new solutions. The air cavity solution seems to be one of the most promising one. Usually, it is very difficult with the experimental tests to understand the air distribution under the hull and the streamlines during the injection of air. The principal objective of this paper is evaluating the potentiality of the CFD approach in the study of Air Cavity Ships (ACS) for a planing yacht. The first part of paper describes the CFD evaluation of the resistance curves without air-injection. The second part deals with the injection of the air under the hull. In this case the boundary conditions are the results of the first campaign of simulations. A comparison between the experimental and CFD results is shown. An assessment of the streamlines and air distribution is proposed and an evaluation of the wetted and ventilated areas is conducted in order to understand the relation between the flow rate, the velocity of the hull and the air distribution. The results can be used for modifying the hull geometry in order to better accommodate the air layer.

Keywords: Air Cavity Ship | Computational Fluid Dynamics | Computer aided engineering | Hull design | Ship resistance

Abstract: 3D virtual reconstruction of human body parts is nowadays a common practice in many research fields such as the medical one, the manufacturing of customized products or the creation of personal avatar for gaming purpose. The acquisition can be performed with the use of an active stereo system (i.e., laser scanner, structured light sensors) or with the use of a passive image-based approach. While the former represents a consolidated approach in human modeling, the second is still an active research field. Usually, the reconstruction of a body part through a scanning system is expensive and requests to project light on the patient’s body. On the other hand, the image-based approach could use multi-photo technique to reconstruct a real scene and provides some advantages: low equipment costs (only one camera) and rapid acquisition process of the photo set. In this work, the use of the photogrammetry approach for the reconstruction of humans’ face has been investigated as an alternative to active scanning systems. Two different photogrammetric approaches have been tested to verify their potentiality and their sensitivity to configuration parameters. An initial comparison among them has been performed, considering the overall number of points detected (sparse point cloud reconstruction, dense point cloud reconstruction). Besides, to evaluate the accuracy of the reconstruction, a set of measures used in the design of wearable head-related products has been assessed.

Abstract: The Strait of Messina is a very busy sea area that separates Sicily and the Italian mainland. In respect of environment and for the prevention of human loss, it is fundamental to have an estimate of the possible ship accidents that could occur. In this work, the approach used is the International Association of Lighthouse Authorities Waterways Risk Assessment Program (IWRAP) model. The first part of the paper describes the local and global traffic and the separation scheme in the Strait of Messina. The model input data is obtained from the Vessel Traffic Service (VTS) system thanks to the Coast Guard of Messina. The second part concerns calculation of the geometrical collisions (number of collisions in different scenarios) and the causation probability. This analysis is the basis for the discussion of new regulatory constraints due to the future realisation of new piers in the south and the planned unification of the two Port Authorities of the two shores into one single authority.

Keywords: Marine traffic safety | Regulatory and environmental constraints | Safety design | Ship collision

Abstract: The present study concerns the environmental impact assessment of a glass-reinforced plastic yacht built with two different technologies: hand lay-up technique and vacuum infusion. The main raw materials are: Glass Fiber, PVC for core and polyester resin. The principal difference between the two manufacturing techniques is the weight of the ship that will influence the production phase, the use phase and lastly the disposal phase. For Life Cycle Assessment for the impact assessment a commercial software has been used, GaBi software with Ecoinvent database. A specific evaluation of resistance of the ship with towing tank tests has been conducted, and an evaluation of the consumption, knowing the engine installed on board. This evaluation is possible thanks to the definition of three different profiles of usage of the yacht (low usage – 200 h/y, medium usage - 350 h/y and high usage – 500 h/y). For every profile, three different cruising conditions: navigation at maximum power (100% of the power on board), sailing cruising (85%) and lastly navigation in economic condition (65%). A curve of fuel consumption to the different percentage of power required is reported; in this way, it is possible for every navigation condition to evaluate the fuel consumption and, consequently, the environmental impact. In this paper is described that a lighter hull, with a reduction in weight of about 9% on deadweight, reduces the fuel consumption of about 656 t of diesel fuel over lifetime, with significant effect in the indicators of environmental impact in Life Cycle Assessment. Although these results may be expected, the use of Life Cycle Assessment has allowed quantifying the reduction of environmental impact in every single phase of the entire lifetime of the boats.

Keywords: Glass reinforced plastic | Green design | Life cycle assessment | Optimization | Vacuum infusion | Yacht

Abstract: Domestic appliance are widely used in all countries. During the design phase, it is very important to take advantage of new virtual prototyping technologies in order to improve the user expectations and put the feeling of the user with the device in the centre of the design. The paper deals with the complete simulation of the opening of the front door of an appliance like a refrigerator or an oven. The process is simulated with the use of ad-hoc built program that uses a combination of experimental parameters and virtual fluid dynamic simulations. Each moment involved during the opening of the door is evaluated and a comprehensive explanation of each of them is reported. The entire solving process is parametrized in order to use it in an iteration loop for eventually optimization of the User Experience and the comfort during the opening of the front door. A fridge case study is described and discussed.

Keywords: Door appliance | Experience design | User centred design | User Experience (UX) | Virtual Prototypes (VPs)

Abstract: Numerous applications involve the use of composite material in order to increase the ratio between strength and weight and in order to increase the flexibility of the design. There is an intensive use of this material also in naval building, principally for recreational boat. Experimental and numerical tests allow having a deep knowledge of the response of this kind of material in different load conditions. In order to accommodate the complexity of the design, usually it is necessary to use bonding for jointing different elements. The work deals with a series of experimental tests for the assessment of the head joint between two carbon laminates. Tests carried out with different angles between the two linked elements in order to evaluate the response of the bonding to different stresses direction. The studied conditions are for 45°, 90°, 135° and 180° with forces applied in both closing and opening direction. The bonding under investigation has a double epoxy resin glues. Thanks to these series of experimental tests is possible to take care about the worst condition of load and try to avoid it during the preliminary phase of design.

Keywords: Adhesive | Bonded joints | Carbon fibre laminates | Nautical design

Abstract: The ships are constrained mainly by mooring lines and fenders to rigid structures such as jetties and piers. The evaluation of the forces that affected the mooring lines and fenders is essential for proper design of all components of the plan such as the chocks, the cables and the bollards. A calculation software that can estimate the loads acting and how they are distributed is essential to be able to perform these calculations with accuracy. The article describes the design phases of the program and the theoretical aspects discussed and is a guide for designers who want to predict the behavior of the mooring plan.

Keywords: Berthing | Environmental forces | Moorings optimization | Safety | Ship design

Abstract: For several years it has been studied how to obtain resistance reduction by means of air injection under the hull. The most studied applications are essentially slow hulls; however, significant results in planing hulls can be achieved. Unfortunately, for this kind of crafts, there are very few experimental data. This study has been performed to compare different cavity shapes, obtained by modifying a mother-hull of a high-speed planing yacht. The design has been obtained with the idea to use the natural low pressure under the bottom of high-speed crafts, in order to stabilize an air-layer instead of the traditional air-cushion. The experimental tests were carried out in a towing tank by varying numerous parameters, including the model speed and the flow rate of air. Results and influence of geometrical and physical parameters are discussed.

Keywords: Air cavity ship | High speed craft | Hull design | Model tests | Ship resistance

Abstract: A geometric tool for a catamarans sail plan and appendages optimization procedure is descripted. The method integrates a parametric CAD model, an automatic computational domain generator and a Velocity Prediction Program (VPP) based on a combination of sail RANS computations and analytical models. The boat performance is obtained, in an iterative process, solving the forces and moment equilibrium system of equations. Hull and appendages forces are modelled by analytical formulations. The closure of the equilibrium system is provided by the CFD solution of the sail plan. The procedure permits to find the combination of appendages configuration, rudders setting, sail planform, shape and trim that maximize the VMG (Velocity Made Good). A significant effort was addressed to the selection and evaluation of open-source tools to be adopted in the implementation of the method. The geometric parametric model, which is the core of the procedure, was object of particular attention. The FreeCAD geometric modeller was sel cted for this task. The sail shapes candidates are automatically generated, within the optimization procedure, by Python scripts that drive FreeCAD to update the geometry according to the variables combination. A very flexible model, able to offer a very wide space of variables, was implemented. This paper describes the implemented geometric model and the environment in which is included.

Keywords: Numerical Optimization | Open-Source | Parametric CAD | Sail design

Abstract: Air-cavity ships (ACS) are advanced marine vehicles that use air injection under hull to improve the vessel’s hydrodynamic characteristics. Although the concept of drag reduction by supplying gas under the ship’s bottom was proposed in the 19th century by Froude and Laval, at this time there are not many systematic studies on this subject. This paper is a preliminary work with the purpose of being a basic tool for the design of the ACS with computational fluid dynamic methods. The study aims to conduct a series of computational tests to compare the numerical models of bubble with experimental data. The first step of this study was to investigate the behavior of free bubble in water, considering as parameters the critical mass of air, the rising speed and aspect ratio of the bubble. Then it is evaluated the interaction bubble-flat plate in order to obtain a reliable prediction of the behavior of air bubbles under the hull.

Keywords: Air Cavity Ship | CFD | High-speed craft design | Hull ventilation | Nautical design

Abstract: In the production of utility poles, used for transmission, telephony, telecommunications or lighting support, for many years, the steel has almost entirely replaced wood. In recent years, however, new composite materials are a great alternative to steel. The questions are: is the production of composite better in terms of environmental impact? Is the lifecycle of composite pole more eco-sustainable than lifecycle of steel pole? Where is the peak of pollution inside the lifecycle of both of technologies? In the last years, in order to deal with new European polices in environmental field, a new approach for the impact assessment has been developed: the Life Cycle Assessment. It involves a cradle-to-grave consideration of all stages of a product system. Stages include the extraction of raw material, the provision of energy for transportation and process, material processing and fabrication, product manufacture and distribution, use, recycling and disposal of the wastes and the product itself. A great potentiality of the Life Cycle assessment approach is to compare two different technologies designed for the same purpose, with the same functional unit, for understanding which of these two is better in terms of environmental impact. In this study, the goal is to evaluate the difference in environmental terms between two different technologies used for the production of poles for illumination support.

Keywords: Green Design | Life Cycle Assessment | Manufacturing optimization | Utility poles

Abstract: In the last decade, sandwich composite materials have had an increasing use in design of racing boats. The main reasons are: higher strength-weight ratio, low density, excellent durability and versatility. The knowledge of impact response is very important to design racing boats. The aim of the present study is the investigation of absorbing impact energy ability of a sandwich composite material used for offshore vessels in UIM (Unione Internationale Motonautique) Championship. The material analysed in this study is a sandwich manufactured with hand lay-up technique. In the first phase, the damage assessment of single impact has been studied with an optical measurement technique. In a second phase, the damage evaluation due to repeated impacts has been analysed with the similar technique.

Keywords: Damage accumulation | Lightweight composites | Low energy impact | Nautical applications | Optical mesaurements | Safety design