Documents published in Scipedia

• Optimum design method for artificial ear ossicles based on a high-precision vibration analysis model

  Y. Liu

  WCCM2024.

  
  

  Abstract

  In this study, we propose a topology optimization approach aimed at designing an optimal artificial auditory ossicle to enhance hearing restoration in the sound conduction reconstruction of a damaged human middle ear. The primary objective of our design is to maximize the vibration displacement of the stapes footplate by employing the concept of mutual mean compliance. Using this method, we can determine the optimal topology configurations of the artificial component based on topology sensitivity, which we theoretically derive in this paper. To demonstrate the effectiveness and practical utility of our proposed approach, we present a design example of artificial auditory ossicles utilized in tympanoplasty procedures.

  Abstract
  In this study, we propose a topology optimization approach aimed at designing an optimal artificial auditory ossicle to enhance hearing restoration in the sound conduction [...]

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• Markov chain Monte Carlo capabilities in Dakota

  E. Prudencio, A. Stephens

  WCCM2024.

  
  

  Abstract
  We give an overview of MCMC capabilities in the Dakota software package from Sandia National Laboratories, and present some Bayesian calibration results.

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• Modelling and simulation of a fully electric hybrid propulsion system for passenger ships using AVL Cruise-M software

  L. Micoli, R. Russo, T. Coppola, D. Severi

  WCCM2024.

  
  

  Abstract

  The maritime industry's pursuit of sustainability drives the exploration of alternative fuels, with hydrogen emerging as a promising solution. This paper presents a comprehensive study on a fully electric hybrid propulsion system for passenger ships, utilizing hydrogen as the primary power source. Multi-physics simulation using AVL Cruise-M software enables detailed analysis of system dynamics and performance. Results from a full acceleration test reveal the intricate interplay between the fuel cell and battery system, crucial for meeting power demands during transient phases. Examination of material flows highlights the importance of maintaining optimal water balance for system efficiency and durability. Temperature and pressure variations significantly influence FC efficiency, showcasing improvements over time, stabilizing at approximately 56% efficiency after 2.6 minutes. These findings underscore the value of comprehensive simulations and temporal analysis in optimizing hybrid propulsion systems, suggesting strategies for further enhancement, such as precise temperature and mass flow control.

  Abstract
  The maritime industry's pursuit of sustainability drives the exploration of alternative fuels, with hydrogen emerging as a promising solution. This paper presents a comprehensive [...]

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• Understanding the solidification and heat treatment characteristics in the CoCrNiSix medium-entropy alloy by experimentally verifiable multiscale thermodynamic and kinetic computational techniques

  T. Su, H. Huang, J. Chen

  WCCM2024.

  
  

  Abstract

  CoCrNi medium-entropy alloy (MEA) possesses an FCC crystal structure with multiple slip systems and low stacking fault energy [1]; a substantial amount of nanoscale deformation twins can be generated under low-temperature and high-speed deformation. Adding a proper amount of Si can not only reduce the manufacturing cost and mass density but also enhance ballistic resistance by further lowering the stacking fault energy. Previous studies [2] utilized small-scale vacuum arc remelting techniques to investigate the solid solution or secondary phase strengthening of CoCrNi-based MEAs with Al or Si additions. However, to extend the application of lightweight, high-entropy alloys to industrial-grade impact-resistant plate manufacturing, especially for low-temperature environments, it is necessary to study the solidification and heat treatment characteristics of CoCrNiSix castings. This study employs finite element analysis at the macroscopic scale to investigate the solidification phase transformation and heat transfer characteristics of CoCrNiSix under precision-cast conditions. Additionally, at the mesoscopic scale, the phase-field method [3] is used to simulate the dendritic solidification microstructure and element segregation of CoCrNiSix. Thermodynamic parameters required for simulations are calculated using Thermo-Calc high-entropy alloy databases TCHEA6 and MOBHEA2. This research also utilizes electron microscopy to analyze the microstructures of chemically complex CoCrNiSix ingots, focusing on measuring the secondary dendrite arm spacing and elemental segregation profiles. Collecting these microstructure-related features allows us to reasonably infer the cooling rate corresponding to the investment casting process of CoCrNiSix and design rational parameter combinations for homogenization heat treatment of the cast ingots in terms of temperature and isothermal holding time. By validating macroscopic and mesoscopic simulation results through CoCrNiSix microstructure analysis experiments, the multiscale kinetic computational techniques included in this study can be further applied to cost-saving and process optimization practices in the manufacturing of various lightweight high-entropy alloys

  Abstract
  CoCrNi medium-entropy alloy (MEA) possesses an FCC crystal structure with multiple slip systems and low stacking fault energy [1]; a substantial amount of nanoscale deformation [...]

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• Space-time Galerkin finite element discretization and error control for coupled problems

  T. Wick, P. Junker, J. Thiele, J. Roth

  WCCM2024.

  
  

  Abstract

  In this work, we consider one key component, namely the wave equation, of a recently proposed space-time variational material model. The overall model is derived from a thermodynamically consistent Hamilton functional in the space-time cylinder in which mechanics, temperature and internal variables couple. Through the derivation, rather unusual end time conditions for the second-order in time wave equation arise. In order to understand their behavior better, we solely focus on the wave equation (neglecting temperature and internal variables) and formulate a Galerkin finite element discretization in time and space. Based on this discretization and the corresponding implementation, some numerical simulations are conducted. Therein, both traditional initial conditions for the displacements and the velocities are considered, as well as our newly proposed conditions for initial time and final time acting on the velocity variable only

  Abstract
  In this work, we consider one key component, namely the wave equation, of a recently proposed space-time variational material model. The overall model is derived from a thermodynamically [...]

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• Goal oriented error estimation for space-time adaptivity in phase-field fracture

  V. Kosin, A. Fau, F. Hild, T. Wick

  WCCM2024.

  
  

  Abstract

  This work focuses on temporal adaptivity for phase-field fracture problems. The methodology requires a space-time formulation and utilizes a space-time Galerkin finite element discretization for the governing phase-field equations. Then, goal functionals (i.e., quantities of interest) are introduced. The computational implementation of goal-oriented error control employs the dual-weighted residual method in which an adjoint problem must be solved. As the analysis is quasi-static, without a temporal derivative, the adjoint problem of the quasistatic primal problem decouples in time. Nonetheless, time-averaged goal functionals can also be considered. The temporal errors are localized using a partition of unity, which allows one to adaptively refine and coarsen the time intervals in the space-time cylinder. Numerical tests are performed on a single edge notched tensile test to investigate the quality of the proposed error estimator.

  Abstract
  This work focuses on temporal adaptivity for phase-field fracture problems. The methodology requires a space-time formulation and utilizes a space-time Galerkin finite element [...]

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• Assessment of flow-induced stresses in spiral weld pipes with bends

  S. Ahmadizade, S. Verma, A. Hemmati

  WCCM2024.

  
  

  Abstract

  This study numerically investigates flow-induced stresses and displacements in bent pipes at varying angles (20◦ ≤ θb ≤ 80◦ ) using Solids4Foam at Reynolds number of 20,000. The results indicate that increasing θb enhances the formation of symmetric vortex structures, which coincide with enhanced non-uniformity in pressure distribution and wall shear stresses. Additionally, maximum equivalent stresses (σeq) for the solid shell occur near the inlet. The pipes with higher θb also depict a reduced displacement magnitude(D), which hints at the strong role of fixed displacement boundary condition assigned at the pipe inlet and outlet. These findings provide essential insights for performing numerical investigation of pipeline reliability and structural integrity in oil transportation.

  Abstract
  This study numerically investigates flow-induced stresses and displacements in bent pipes at varying angles (20◦ ≤ θb ≤ 80◦ ) using Solids4Foam at Reynolds number [...]

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• Computational interpretation of shape memory epoxy: processing and its operation

  Y. Kim, H. Kim, J. Choi

  WCCM2024.

  
  

  Abstract

  The shape forming and restoration mechanisms of shape memory epoxy originate from the molecular-scale dynamics that epoxy molecules undergo during thermomechanical processes. In this study, the microstructural changes that occur at the molecular scale caused by heat and load during the programming and operation of the epoxy network were investigated using molecular dynamics simulations. The mechanical behaviors of each molecule were analyzed by classifying it into translation, rotation, and deformation based on the classical kinematic framework. Specifically, depending on its structural properties, each molecular component was rearranged to different levels, forming local residual stresses. The principle leading to shape recovery as the subsequent thermal load breaks the equilibrium of residual stresses and resulting changes in the mechanical anisotropy of entire epoxy network were also analyzed through a subcontinuum perspective. This study has the potential to be extended to a method for designing epoxy resins that satisfy desired physical properties and shape recovery performance

  Abstract
  The shape forming and restoration mechanisms of shape memory epoxy originate from the molecular-scale dynamics that epoxy molecules undergo during thermomechanical processes. [...]

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• An improved flux vector splitting method for characteristic-wise WENO schemes of the Euler equations

  J. Kim, Y. Shen

  WCCM2024.

  
  

  Abstract

  Steger-Warming (SW) [1] and Lax-Friedrich-type (LF) [2] flux vector splitting methods are used extensively by shock capturing WENO schemes in varieties of compressible flow simulations. Due to the less dissipation, the SW method is preferred in flow calculations that require fine scale structures such as direct numerical simulation of turbulence. However, this paper shows that, even if the characteristic-wise WENO scheme is used, the SW method may still exhibit some oscillations near contact discontinuities, while the LF method does not. Analysis similar to the reference [3] shows that, using the SW method may make the characteristic-wise WENO scheme become close the component-wise WENO scheme near subsonic contact discontinuities. Based on that, an improved flux vector splitting method, which adjusts the eigenvalues of the flux vector splitting in the characteristic-wise WENO procedure, is proposed to obtain the low-dissipation property and prevent contact discontinuity oscillations at the same time. Numerical experiments are performed to validate and evaluate the new method. Numerical results show that the proposed method keeps the non-oscillatory flow field near discontinuities as LF method and also avoids smearing out other flow regions, similar to the SW method.

  Abstract
  Steger-Warming (SW) [1] and Lax-Friedrich-type (LF) [2] flux vector splitting methods are used extensively by shock capturing WENO schemes in varieties of compressible flow [...]

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• Modeling the enhanced geothermal systems using the extended–FEM and an equivalent continuum model

  A. Khoei, S. Mortazavi, O. Rezaie Beydokhti, P. Pirmoradi

  WCCM2024.

  
  

  Abstract

  . In this paper, a computational technique is presented for Thermo-Hydro-Mechanical (THM) simulation of Enhanced Geothermal Systems (EGS) based on the eXtended Finite Element Method (XFEM) and Equivalent Continuum Method (ECM) in the framework of Local Thermal Non-Equilibrium (LTNE). Heat extraction from Enhanced Geothermal Systems involves several multi-physics coupling processes, including the seepage through the fractured porous media, the thermal exchange between the working fluid and the matrix, and the deformation of fractured porous media that play essential roles in exploiting the geothermal energy contained in hot dry rocks. The ECM provides the equivalent tensors for the fluid permeability and solid compliance, which is an essential feature for the coupled Thermo-Hydro Mechanical simulation of fracture networks. In the model, the XFEM is employed for large scale fractures to capture the mass and heat transfer between the fracture and matrix more accurately, while the ECM is applied on the network of small-scale fractures. Hence, the proposed model benefits from the advantages of both methods, and it allows for managing between accuracy and cost. The set of THM equations is solved with both Local Thermal Equilibrium (LTE) and Local Thermal Non-Equilibrium (LTNE) assumptions to find out the impact of each method on the production temperature. The capability of the proposed computational model is demonstrated for the diagonal arrangement of the injection and production wells with different fracture orientations in-between. The simultaneous effects of fracture connectivity and inclination are investigated between the two injection and production wells. It is observed that the temperature difference between the two cases is higher in the middle of the domain by comparing the results of LTE and LTNE assumptions. Moreover, it is concluded that the LTE model overestimates the fluid temperature in comparison to the LTNE model in cold water injection problems. The results show the proposed computational model is a promising tool for estimation of the heat mining performance of EGS

  Abstract
  . In this paper, a computational technique is presented for Thermo-Hydro-Mechanical (THM) simulation of Enhanced Geothermal Systems (EGS) based on the eXtended Finite Element [...]

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