Documents published in Scipedia

• Coupling multiple resonances for enhancing sound transmission loss of acoustic metamaterials

  D. Roca, G. Sal-Anglada, D. Yago, J. Cante

  WCCM2024.

  
  

  Abstract

  Recent developments in acoustic metamaterials have been focused on broadening the attenuating bandwidth features towards lower frequency ranges, well below 1000 Hz, as well as tackling manufacturing issues. In this context, a multi-resonant layered acoustic metamaterial (MLAM) was proposed as a practical realization for addressing both challenges. The MLAM’s layered-based design makes it amenable to large-scale manufacturing and the periodic features of each layer enable the application of computational homogenization models to characterize the sound transmission loss (STL) response. Combining these models with optimization techniques allows to determine realistic MLAM designs that trigger multiple resonances in broad frequency ranges. By exploiting coupling mechanisms these resonances translate into multiple STL peaks that produce a broadband continuous frequency range of attenuation, i.e., without transmission peaks in-between. In this work, the proposed computational homogenization model is presented and applied to the design of different MLAM configurations. The goal is to assess the influence of the number of coupled resonating layers in the STL response of the whole MLAM panel, in terms of increasing the attenuation intensity and the effective frequency bandwidth. The results demonstrate the STL enhancements features obtained from exploiting coupling mechanisms, compared to other acoustic metamaterial configurations based on local resonance phenomena. In this context, the proposed MLAM technology exhibits a great potential to provide an efficient, easy-to-manufacture solution to the sound insulation problem at low frequency ranges

  Abstract
  Recent developments in acoustic metamaterials have been focused on broadening the attenuating bandwidth features towards lower frequency ranges, well below 1000 Hz, as well [...]

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• Application of the Harmonic Balance Method to predict wave propagation in one-dimensional nonlinear metamaterial excited harmonically

  R. Moura Barbosa, A. Serpa

  WCCM2024.

  
  

  Abstract

  This work exposes a computational procedure designed to aid in modeling mechanical systems featuring stiffness nonlinearity. The basis of the procedure is the Harmonic Balance Method, which is combined with a numerical continuation technique. To present the efficacy of the approach, a one-dimensional nonlinear metamaterial is analyzed. The aim is to demonstrate the suitability of the procedure to extract information regarding higher harmonic generation and the influence of the amplitude of excitation on the system dynamic response.

  Abstract
  This work exposes a computational procedure designed to aid in modeling mechanical systems featuring stiffness nonlinearity. The basis of the procedure is the Harmonic Balance [...]

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• Ritter-Križaić iteracion method of truss constructions

  V. Križaić, T. Rodiger, N. Križaić, J. Križaić

  WCCM2024.

  
  

  Abstract

  The optimization of the dimensioning of constructive designs is constantly evolving. FEM, evolutionary, and other various methods are being developed, which are implemented with algorithms in computer simulations of building models. The problem with these methods is solving large differential equations, which is inconceivable without computers and large memories. The Ritter-Križaić (RK) iteration method works for both straight and oblique networks with one side, and it can even be used instead of trigonometric and FEM equations. It does this by adding the geometric properties of the networks and outside actions to the directional equations. By creating straightforward monograms of RK-FEM technology with straightforward differential or subspace equations that are simple to calculate by hand or draw with Mathcad tools, the RK-FEM loop enables COD to define various types of trusses and even other supports. RK-FEM COD is therefore used to create simulation games that explain many logical phenomena in the design of external and internal actions of beam supports, which can be compared to a spider thread or an ice plate structure as an RK string and even to the moon

  Abstract
  The optimization of the dimensioning of constructive designs is constantly evolving. FEM, evolutionary, and other various methods are being developed, which are implemented [...]

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• Influence evaluation of flow diverter stent parent vessel coverage on cerebral aneurysm through the CFD-DEM coupling simulation

  Y. Ohkura, D. Watanabe, R. Taniguchi, S. Yamani

  WCCM2024.

  
  

  Abstract

  Cerebral aneurysms are a type of cerebrovascular disorder where a balloon-like bulge forms in part of an artery in the brain. One of the developed treatments for large cerebral aneurysms is the Flow-diverter Stent (FDS) placement technique. Effective treatment outcomes in cerebral aneurysm treatment using FDS require proper placement of the device. Improper placement can lead to increased blood flow velocity and Wall Shear Stress (WSS) within the aneurysm, as well as increased pressure, which suggests a potential risk of rupture in large aneurysms. Considering these circumstances, this study evaluates the impact of FDS positioning on cerebral aneurysms by creating multiple FDS placement models with the device positioned proximally and distally to the aneurysm. Subsequently, we conducted fluid-structure interaction simulation analyses using the Particle Finite Element Method-Second Generation (PFEM-2) for the non-Newtonian fluid model of blood and the Discrete Element Method (DEM) for the FDS. This study reports the results of comparing blood behavior, WSS, and pressure inside the cerebral aneurysm based on the FDS placement position.

  Abstract
  Cerebral aneurysms are a type of cerebrovascular disorder where a balloon-like bulge forms in part of an artery in the brain. One of the developed treatments for large cerebral [...]

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• Delta-P1 model implementation for numerical simulation of photothermal cancer therapy in three-dimensional heterogeneous tissues

  R. Gomez Araque, C. Bustamante, R. Valencia, W. Florez

  WCCM2024.

  
  

  Abstract

  Photothermal therapy (PTT) stands as a promising avenue for cancer treatment. Metallic nanoparticles (NPs) absorb near-infrared light, inducing localized heating for tumor cell apoptosis. Predicting spatial temperature information in preclinical models is crucial due to cell death sensitivity to temperature changes. Heat transfer models, rely on the radiative transport equation (RTE), where its approximation is essential for this purpose. Existing models for the radiative transport equation, such as the Beer-Lambert law, the diffusion approximation, the discrete ordinates method, and Monte Carlo (MC) simulations, are widely used in the context of PTT. However, each of them has limitations. This study focuses on the δP1 model, wich is an extension of the diffusion approximation. Unlike standard diffusion approximation (SDA), the δP1 model treats forward and scattered light independently, preserving accuracy over a wider range of optical properties, including media with plasmonic NPs. The δP1 model equations are discretized and solved by the Finite Element Method (FEM) . Its numerical results for fluence rate in a heterogeneous geometry with nanoshells is compared to MC simulations and the standard diffusion approximation. This study validates and applies the model to the simulation of light transport in photothermal therapy in general two-dimensional geometries. Results demonstrate the δP1 shows a significant improvement over the SDA in heat transfer simulations in heterogeneous tissues geometries. This underscores its potential as a valuable tool for optimizing photothermal therapy preclinical models.

  Abstract
  Photothermal therapy (PTT) stands as a promising avenue for cancer treatment. Metallic nanoparticles (NPs) absorb near-infrared light, inducing localized heating for tumor [...]

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• 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 [...]

  • 132
  •  read