C11
Multiphysics 6

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10:40
conference time (CEST, Berlin)
A Numerical Framework for the Simulation of Stimuli-responsive Polymer Gels for the Application as Actuators
27/10/2021 10:40 conference time (CEST, Berlin)
Room: C
A. Attaran (IMO Holding GmbH, DEU); P. Gebhart, T. Wallmersperger (TU Dresden, Institute of Solid Mechanics, DEU)
A. Attaran (IMO Holding GmbH, DEU); P. Gebhart, T. Wallmersperger (TU Dresden, Institute of Solid Mechanics, DEU)
In the present work, a numerical framework to simulate the bending and actuation behavior of stimuli-responsive polymer gels is presented. Specifically, polyelectrolyte gels (or hydrogels) and magnetic gels (or ferrogels) of permanent network structures, i.e., chemical gels, are investigated. The former is usually regarded as electroactive gels in the literature, while the latter falls into the category of magnetoactive gels. The response of a polymer gel to environmental changes is usually realized in the form of conformational changes. Swelling of a polymer gel due to the pH variation of the system, bending of a polyelectrolyte gel because of an externally applied electric field, and elongation of a magnetic gel sphere in a magnetic field are examples of such conformational changes. The modeling approach is based on the multicomponent, multiphase nature of hydrogels and ferrogels. The constituents of hydrogels and ferrogels, therefore, need to be identified. The theory of mixtures is adopted for derivation and presentation of the respective field equations along with the theory of electromagnetism. Using the procedure introduced, a coupled chemo-electro-mechanical formulation for hydrogels and a magneto-mechanical formulation for ferrogels are achieved. Both formulations are numerically treated in 2D using the finite element method. Using the developed numerical procedure, the actuation mechanism of the polymer gels under study can be simulated. For hydrogels, the aim is to simulate the local bending deformation under the electrical stimulation for the application as hydrogel grippers. A system consisting of both an anionic gel and a cationic gel, immersed in NaCl solution bath, is considered. By the application of an electric field between two electrodes on the top and bottom of the solution bath, gels bend towards or away from each other, mimicking the closing and opening of a hydrogel gripper. Deformation (elongation or contraction) of ferrogels under an applied magnetic field is also simulated using the finite element method. By the finite element simulation, elongation of a ferrogel is observed parallel to the applied magnetic field and contraction of a ferrogel is seen perpendicular to the applied magnetic field. With the modeling approach of the present work, the resulting mechanical deformation of a ferrogel, in an applied magnetic field, can be determined.
Finite Element Analysis, Multiphysics, Coupled Multi-field Formulation, Stimuli-responsive Polymer Gels, Actuators and Sensors
11:00
conference time (CEST, Berlin)
Two-Way Coupled Thermal-Electric Simulation of a Packaged Laserdiode using Reduced Order Models
27/10/2021 11:00 conference time (CEST, Berlin)
Room: C
T. Moldaschl, G. Grosso (SAL Silicon Austria Labs GmbH, AUT); R. Fuger (CADFEM ,AUT)
T. Moldaschl, G. Grosso (SAL Silicon Austria Labs GmbH, AUT); R. Fuger (CADFEM ,AUT)
Laser diodes have many applications in different areas of research and technology and underly different working principles. Semiconductor Lasers are of most importance as they can be produced using established semiconductor manufacturing processes. A Quantum Well (QW) Laser Diode is used in this report as a powerful light source for automotive LIDAR applications. Especially the extended automotive environment conditions require a special selection of elements and materials and require specific cooling solutions. In order to evaluate a LIDAR system with its high power densities the Laser diode is simulated both electrically and thermally to find crucial elements that are electrical and thermal bottlenecks. The electrical System is analyzed with Ansys Maxwell and the thermal system with Ansys Mechanical and they are both coupled through a transient Ansys TwinBuilder simulation. Both systems comprise the same geometry, a fourfold bonded edge emitting QW Laser with connection pads in a molded package. Each of the four Lasers on a single chip can be addressed separately and is connected through a gold bond wire and a copper pin. In order to obtain 2-way coupling, electrical losses from the Maxwell simulation are coupled into a transient thermal simulation using Mechanical. The resulting temperatures are then fed back into the electrical simulation, where the conductive copper has been assumed to be temperature dependent, and thus, also the losses are temperature dependent. Each simulation in either Maxwell and Mechanical requires a separate FEM simulation to obtain the losses or the temperatures. To obtain coupling in this way would require a very long simulation time for a two-way coupling scheme. In order to speed up the process the electrical simulation is transformed into reduced order model (ROM) using a functional mockup unit comprising a sufficiently large input parameter space and a thermal LTI ROM system using all separate loss inputs. For each parameter combination in both Maxwell and Mechanical a complete FEM simulation must be run. But once the data is available, the ROMs are created and a transient simulation in TwinBuilder can be run with significant reduction of simulation time. We present simulation results of this system using only ROMs, compared to full FEM simulations and discuss the advantages and implications of using only ROMs.
reduced order models, FEM Simulation, Ansys Maxwell, Ansys Mechanical, Coupled Multi-Physics Simulation
11:20
conference time (CEST, Berlin)
FSI Analysis of Flow Around an Elastic Plate Behind a Rigid Circular Cylinder- A Parametric Study
27/10/2021 11:20 conference time (CEST, Berlin)
Room: C
M. Cakir, W. Malalasekera (Loughborough University, GBR)
M. Cakir, W. Malalasekera (Loughborough University, GBR)
This paper presents a 3D numerical analysis of a well-known fluid-structure interactions (FSI) test case, namely the benchmark of Turek & Hron. The study aims to understand and analyse the fundamental characteristics of FSI through a simple test case. Therefore, a fully developed laminar flow at Re=200 has been studied using a single-platform coupling methodology adapted by STAR-CCM+ CFD software. From the study, the following results: displacements at the end of the plate; lift and drag forces on the interface are obtained. The work undertaken here mainly consists of a validation and a parametric study. Initially, the computational results have been validated with numerical results reported in the literature, and then a comprehensive parametric study is performed. For the parametric study, the selection of materials, geometric dimensions and coupling methods have been considered as the key parameters for the modelling of FSI problems. Therefore, polybutadiene, polypropylene, and steel were used as solid materials whereas glycerin, air and water were used as fluids. For geometric parameters, the plate dimensions were modified in terms of length and thickness. Regarding coupling methods, one-way and two-way coupling method were used at the solution of the problem. The results show that simulation results and literature data match well with each other. Relative differences between fluid and solid material properties affecting the characteristic have been analysed. For geometric features, the results demonstrate how the formation of flow-induced oscillations are influenced by the changes in the length and thickness of the plate. Furthermore, it is seen from the results that two-way coupling method gives far better results than the one-way coupling method, although one-way method gives faster results compared to the other. Consequently, it can be stated that analysis and validation of a single-platform FSI modelling strategy as in this study allows the simulation of full-scale systems that exist in engineering applications.
Flow-induced oscillations, FSI, flexible plate, laminar flow, STAR-CCM+, one-way and two-way coupling.
11:40
conference time (CEST, Berlin)
CFD and Radiation Model of a Highly Nonlinear Glass Forming Process
27/10/2021 11:40 conference time (CEST, Berlin)
Room: C
W. Hoffmann (SiCo Solutions, DEU); T. Bernard (Fraunhofer IOSB, DEU); R. Wulfert, Q. Ma (Heraeus Quartz North America LLC, USA)
W. Hoffmann (SiCo Solutions, DEU); T. Bernard (Fraunhofer IOSB, DEU); R. Wulfert, Q. Ma (Heraeus Quartz North America LLC, USA)
In this paper, we address the modeling of a complex glass forming process. The aim of the process is the production of rods and tubes with very tight specification of diameter and wall thickness. Modeling this process via simulations has two key benefits: (1) It provides deep insights into aspects that are inaccessible to available measurements. This allows, e.g., to better cope with real world disturbances, such as asymmetries of the furnace. (2) Advanced control strategies can be developed through experimentation and verification with the simulation model. We implement the glass formation process in terms of fluid dynamics (CFD), modeling the glass body as a fluid domain bounded by free surfaces including surface tension. The evolving shape is then calculated via interface tracking in conjunction with Stokes flow, where the melting of the glass is modeled by a viscosity with fitted temperature dependence. In our paper/presentation, we present the general setup of the model (which is implemented in COMSOL Multiphysics). A crucial issue is the accurate modeling of the radiative heating of the glass body as well as the heat transfer throughout the glass. We present different approaches to implement a radiation model, specifically the Rosseland and P1 approximations as well as variants of these approaches. For the heat exchange between oven and glass, we use a Surface-to-Surface (S2S) interface. Unfortunately, this does not account for the radiation penetrating the glass. We show how, as a practical solution, the incoming surface radiation can be coupled as a boundary source to a Radiation in Participating Media (RPM) interface. As a result, the temperature distribution in the glass becomes more realistic. We show some simulation results, which illustrate the problem as well as the improvements regarding the radiative heat transfer. We will present some applications demonstrating the quality and realism of the model.
CFD, radiation, glass forming process, free surface deformation
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