Documents published in Scipedia

• Development of a land use classification model based on semantic segmentation using aerial photographs and its application to Tsunami simulation

  Y. Habutsu, T. Miyake, H. Okawa, K. Kashiyama

  WCCM2024.

  
  

  Abstract

  This paper presents a development of land use classification model based on semantic segmentation using aerial photographs and its contribution to the efficiency of 2D tsunami inundation simulations. The proposed method uses Artificial Intelligence(AI)-based image classification to generate a roughness coefficient mesh, which is then applied to a 2-D tsunami run-up simulation using the finite element method on real geometry. Numerical results are compared to evaluate the improvement in simulation efficiency, and the potential benefits of the proposed method are discussed by analyzing the differences in simulation results.

  Abstract
  This paper presents a development of land use classification model based on semantic segmentation using aerial photographs and its contribution to the efficiency of 2D tsunami [...]

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• Research on heat distribution design of carbon ceramic brake discs and shape optimization of rib for high-speed train

  Y. Zhou, S. Yao

  WCCM2024.

  
  

  Abstract

  High speed and lightweight are the development trends of high-speed trains in the world. Air braking technology is the last line of defense to ensure the safety and reliability of trains. The complex working environment and huge braking power put forward higher requirements for brake disc configuration and material. Carbon-ceramic composite materials have the characteristics of large specific heat capacity, thermal shock resistance, lightweight and high temperature resistance, and are considered to be high-performance friction materials. By imitating the distribution of animal and plant nutrients transportation pipelines, a carbon-ceramic composite brake disc structure with #-shaped heat dissipation ribs was designed that take into account the anisotropy of the thermal conductivity of carbon-ceramic composite materials. The branched rib structure realizes rapid heat transmission in the disc material, thereby achieving high efficiency and uniform temperature distribution, prevents the concentration of heat generated by friction, which can reduce the maximum temperature value under braking conditions. Then combined with the shape optimization and size optimization design of the local heat dissipation ribs of the brake disc. Further research on the uniform temperature performance and heat dissipation under emergency braking conditions of 400km/h was carried out. The LSR model was used to analyze the different outlet angle, inlet angle and number of the cooling ribs in the same reference flow field. By comprehensively considering parameters as the average maximum temperature, convection heat transfer coefficient, an optimal design that balances cooling efficiency and aerodynamic loss is obtained.

  Abstract
  High speed and lightweight are the development trends of high-speed trains in the world. Air braking technology is the last line of defense to ensure the safety and reliability [...]

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• Pratt truss characteristics for optimal weight

  A. Neiburgs

  WCCM2024.

  
  

  Abstract

  This paper presents a study on the characteristics of Pratt trusses under conditions of optimal or near-optimal weight. Trusses with varying numbers of panels, spans, and heights are selected for analysis. Several characteristics describing truss geometry and internal forces are examined. Four dimensioning approaches are developed to perform calculations and obtain data for analysis. A parametric model of truss geometry is developed and integrated with a finite element calculation algorithm in the Rhino8/Grasshopper software. The data are processed and analyzed using the machine learning software Weka and the statistical analysis software RStudio. Results show correlations between various truss characteristics. This study focuses on truss weight and height-span ratio to find the optimal weight. Based on truss height at optimal weight for each span, other characteristics are analyzed. It is observed that a larger number of panels increases the truss weight but also makes the results more consistent and predictable. The objective of this work is to better understand Pratt truss performance, which can be used to reduce the size of optimization tasks.

  Abstract
  This paper presents a study on the characteristics of Pratt trusses under conditions of optimal or near-optimal weight. Trusses with varying numbers of panels, spans, and [...]

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• Finite element-based simulation of large wind turbines wake using the actuator line method

  V. Morici, V. Barnabei, A. Castorrini, F. Rispoli

  WCCM2024.

  
  

  Abstract

  The numerical simulation of wind turbines and wind farms aerodynamics represents an open challenge in computational mechanics. It involves multi-physics and multi-scale phenomena, turbulent flows at very large Reynolds numbers, atmospheric boundary layer features, and rotor machinery flow features and dynamics. The geometrically resolved Computational Fluid Dynamics (CFD) is recognized as the highest-fidelity approach for wind turbine simulations but it has still a too high computational cost if employed for wind farm flow analysis. For this application, several reduced-order models have been formulated to obtain reliable results at a sustainable computational effort. Among the others, Large Eddy Simulations (LES) with Actuator Line Model (ALM) represents a valid middle-fidelity alternative for accurately simulating the wind turbine wakes dynamics and its interaction with the atmospheric boundary layer turbulence. Most implementations of the ALM are derived for volume-based CFD solvers. In this work we present the implementation of this model in a Finite Element Method (FEM) framework, which allows the use of a Residual Based Variational Multiscale (RBVMS) method to model the turbulent flow field, instead of the standard LES formulation. The ALM-VMS formulation is applied to study a 5MW and a 15MW wind turbine rotors, comparing the results with data available in literature in terms of aerodynamic variables of main interest, such as rotor loads and aerodynamics and near and far wake features.

  Abstract
  The numerical simulation of wind turbines and wind farms aerodynamics represents an open challenge in computational mechanics. It involves multi-physics and multi-scale phenomena, [...]

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• Compressive stocking optimization for lymphedema treatment at lower-limb

  A. Garcia Llona, M. Aguirre, F. Verdugo, S. Avril

  WCCM2024.

  
  

  Abstract

  Lymphedema is a chronic disease that causes swelling in the soft tissues, mostly taking place in the extremities. This research focuses on the treatment of lymphedema through compression, which is widely applied to reduce the volume of edemas. Although effective at a clinical level, the use of off-the-shelf stockings with predefined sizes, reduces the efficiency at the patient-specific level. With the long-term goal of designing patient-specific stockings, this study aims to develop a real-time simulation tool, able to predict the efficiency of a given compression stocking for a given patient. For such purpose, the use of standard Finite Element Method (FEM) falls short due to high computational cost. Therefore, a solution based on Reduced Order Modeling (ROM) is developed to compute, in real-time, the hydrostatic pressure distribution at the location of the lymphatic dysfunction. It is assumed that hydrostatic pressure improves lymph circulation and increase the drainage capacity. This method enables to design the most efficient compressive stockings considering the particularities of each patient.

  Abstract
  Lymphedema is a chronic disease that causes swelling in the soft tissues, mostly taking place in the extremities. This research focuses on the treatment of lymphedema through [...]

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• Study of the dynamic behavior of cellular structures for the absorption of mechanical vibrations

  M. Silva, L. Ramos

  WCCM2024.

  
  

  Abstract

  Vibration is a prevalent issue in structural engineering, encompassing a wide array of problems that, if left unaddressed, can lead to severe consequences. These consequences can vary from causing discomfort for pedestrians traversing a perceptibly moving bridge to inducing premature fatigue in aeronautical structural components, ultimately resulting in catastrophic failures and loss of human life. Various sources can induce vibration in structural components, such as misalignment of rotating systems, seismic excitations, road loads on vehicles, and aerodynamic loads. To address these phenomena, in addition to appropriate structural design, various mechanisms, which can operate actively or passively, are used to attenuate oscillatory effects and minimize their impact. Active systems use electronic controllers to generate a response via actuators, reducing the signal transmissibility level based on specific oscillatory signals. Passive systems, on the other hand, mainly rely on viscoelastic polymeric materials, utilizing the reduction of the natural frequency associated with their use and a characteristic phenomenon of these materials for energy dissipation, hysteresis [1]. Hysteresis is a phenomenon where mechanical deformation energy is dissipated in the form of heat. In other words, part of the energy that would be transmitted to the structure is dissipated, thereby increasing the system's damping. Active systems are extremely efficient in their purpose, as they can isolate vibrations across a wide frequency spectrum and can be applied to structures of different magnitudes, from small and lightweight systems using piezoelectric actuators to large structures using hydraulic actuators, such as in active stabilization systems for reducing vibrations caused by seismic activities in buildings. However, they tend to be quite costly and imply an additional layer of systems, which, if not properly designed, can reduce the structure's reliability [2].

  Abstract
  Vibration is a prevalent issue in structural engineering, encompassing a wide array of problems that, if left unaddressed, can lead to severe consequences. These consequences [...]

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• Investigating the domain of attraction of SDRE applied to a CubeSat attitude control system during launch orbit phase based on cold gas thrusters

  L. Souza, A. Romero

  WCCM2024.

  
  

  Abstract

  The precision of controlling the attitude of a CubeSat during the injection phase in orbit is of fundamental importance for the success of the mission. In general, the CubeSat starts this phase with high angular velocity, and then the controller needs to maneuver the CubeSat to its nominal mode of operation, which is characterized by an attitude of small angles. One way to achieve such a transition between these two modes is by using cold gas thrusters. In this paper, we investigate the region of attraction (ROA) of the State-Dependent Riccati Equation (SDRE) applied to the Attitude Control System (ACS) algorithm during the Launch and Early Orbit Phase which has nonlinear dynamics due to the high angular velocities and perturbations. The SDRE controller is based on cold gas thruster torques to reduce the high angular velocities. The main result of this investigation is the approach to numerically approximate the ROA.

  Abstract
  The precision of controlling the attitude of a CubeSat during the injection phase in orbit is of fundamental importance for the success of the mission. In general, the CubeSat [...]

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• Minimization of vibrations in aeronautical wing spars under flutter situation

  L. Santos, M. Silva, R. Brasil

  WCCM2024.

  
  

  Abstract

  This research project aims to investigate the mitigation of vibrations in the spars of aeronautical wings during flutter occurrences. The study will delve into aeroelastic phenomena, particularly focusing on flutter, defined as the self-excited interaction of vibration modes within a modified system, which can potentially lead to catastrophic failures. An analytical method has been developed to compute the flutter velocity, considering the stiffness and mass matrices, and the utilization of a Tuned Mass Damper (TMD) has been proposed to enhance the flutter velocity, thereby extending the aircraft's operational range. Suggestions for future research directions have been provided.

  Abstract
  This research project aims to investigate the mitigation of vibrations in the spars of aeronautical wings during flutter occurrences. The study will delve into aeroelastic [...]

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• Evaluation of effectiveness of traffic jam absorption driving using computer simulation

  S. Yamada, E. Kita

  WCCM2024.

  
  

  Abstract

  Traffic congestion absorbing driving is a method of driving at low speed with a larger inter-vehicle distance than surrounding vehicles. This makes it possible to reduce excessive acceleration and deceleration, which is effective in alleviating traffic congestion. The traffic simulation in the sag section confirmed that the traffic congestion absorption driving is effective for traffic congestion mitigation. It was shown that it is possible to increase the average speed in congested sections by means of congestion absorption driving.

  Abstract
  Traffic congestion absorbing driving is a method of driving at low speed with a larger inter-vehicle distance than surrounding vehicles. This makes it possible to reduce excessive [...]

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• Enhanced mechanical behavior of nickel-coated graphene graphene reinforced CoCrFeMnNi nanolayered composites

  J. Guan, X. Zhou, G. Qu, G. Bao

  WCCM2024.

  
  

  Abstract

  High entropy alloys (HEAs) especially CoCrFeMnNi HEAs have drawn more and more attention due to their excellent combination performance. However, the mechanical properties of CoCrFeMnNi HEAs still remain to be improved due to the single-phase FCC crystal structure. Although many efforts have been made on strengthening methods by grain refinement or nitriding the improvement of the mechanical properties is still unsatisfactory. To improve the mechanical properties of CoCrFeMnNi HEAs and broaden their application fields, we proposed that adding functionalized graphene in CoCrFeMnNi HEAs and investigated nanoscale mechanical properties and the strengthening mechanism using molecular dynamics (MD) simulation in this paper. The mechanical properties of pristine single-layer graphene nanoplatelets (GNPs) and double-side nickel-coated GNP (Ni-GNP-Ni) reinforced CoCrFeMnNi composites (Ni-GNP-Ni/CoCrFeMnNi) are studied under uniaxial tension by molecular dynamics (MD) simulations. The simulated results show that the mechanical properties of Ni-GNP-Ni/CoCrFeMnNi composites are improved significantly by the addition of Ni coated GNPs. The mechanical properties of Ni-GNP-Ni/CoCrFeMnNi composites exhibit temperature softening and strain rate strengthening effect, and their tensile mechanical properties such as the tensile strength, fracture strain decrease with increasing temperature and enhance with increasing strain rate. It is concluded that the main strengthening mechanisms for Ni-GNP-Ni/CoCrFeMnNi composites are strong interface bonding, effective load transfer from the CoCrFeMnNi matrix to the Ni-GNP-Ni and dislocation/twin strengthening by analysis of the evolution of atomic structure.

  Abstract
  High entropy alloys (HEAs) especially CoCrFeMnNi HEAs have drawn more and more attention due to their excellent combination performance. However, the mechanical properties [...]

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