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Die momentane Konferenzzeit ist: 07. Okt. 2022 04:13:24 MESZ

Poster Session
Dienstag, 28.06.2022:
15:40 - 17:20

Chair der Sitzung: Christophe Saint-Jean, La Rochelle University
Ort: Room MSI 218, Maison des Sciences de l'Ingénieur (MSI), La Rochelle University

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15:40 - 16:00

Thermodynamics of multiple cavitation bubbles interaction with lattice Boltzmann method

He, Xiaolong1; Zhang, Jianmin2; Peng, Haonan3; Yuan, Hao1

1Chongqing Jiaotong University, China, People's Republic of; 2Sichuan University, China, People's Republic of; 3Laboratory for Waste Management, Paul Scherrer Institute, CH, 5232, Villigen PSI, Switzerland

An improved double distribution function (DDF) thermal lattice Boltzmann method is applied to investigate the thermodynamics of multiple bubbles interaction. This model is validated by simulating the evolution process of a laser-produced bubble, and both qualitative and quantitative verification is carried out by comparing with the experimental result and theoretical analysis. The interactions between two vapor bubbles during the collapse process are simulated, and the hydrodynamics and thermodynamics of the cavitation bubble under different influence factors (ie., bubble radius, the distance between two bubbles) are systematically investigated. An attempt was made to give a critical distance to distinguish the weak interaction and strong interaction. Furthermore, the thermodynamics of the bubble cluster is also investigated. The hydrodynamics and thermodynamics during the collapse process in different regions of the cavitation bubble cluster are given. The shielding effect in the outer bubble and the wall effect in the inner bubble is accurately reproduced. Moreover, the temperature superposition effect during the clustered cavitation bubbles collapse process is also proposed.

16:00 - 16:20

Computer simulations of the lymphatic vessels and valves dynamics

Bou Orm, Alaa; Kaoui, Badr

Biomechanics and Bioengineering Laboratory, CNRS, Universite de Technologie de Compiegne, Compiegne, France

The lymphatic system consists of initial lymphatic vessels, which absorb lymph liquid, and collecting lymphatic vessels, which transport the lymph through the lymphatic network and its nodes. The lymph pumping mechanisms is achieved by a cyclic of compression and expansion of the lymphatic vessel wall forced by the surrounding muscles. The lymphatic valves allow pumping the lymph and they prevent its backflow.

We are developing fully coupled two-dimensional fluid-structure computational model to study effects of various parameters on the mechanical behavior of the valves. The lattice Boltzmann method is used to compute the lymph fluid flow and the immersed boundary method to couple the lymph flow with the mechanics of multiple lymphangions and their bicuspid lymphatic secondary valves.

16:20 - 16:40

Assessment of collision operators and forcing schemes in the pseudo-potential lattice-Boltzmann method

Restrepo Cano, Juan Guillermo1; Hernandez Perez, Francisco E.1; Lei, Timan2; Luo, Kai2; Im, Hong G1

1King Abdullah University of Science and Technology, Saudi Arabia; 2University College London, United Kingdom

In this work, a multiphase pseudo-potential lattice-Boltzmann (PP-LB) model was implemented to compare the numerical performance of different collision operators and forcing schemes in terms of the spurious velocities, accuracy, and computational cost. The single-relaxation time (SRT), the 2nd and 3rd-order multi-relaxation time (MRT), and the central moment (CM) collision operators are included in the comparison. In addition, the exact difference method (EDM) was incorporated, along with two improved formulations for Guo’s forcing scheme, as proposed by Li et al. (2012) and Huang & Wu (2016), that satisfy the mechanical stability condition. The different combinations of collision operators and forcing schemes were studied using the Carnahan-Starling (CS) and Peng-Robinson (PR) equations of state (EOS) for a two-dimensional stationary droplet. The predicted equilibrium densities given by the PP-LB method show a remarkable agreement with the theoretical coexistence curve and the coexistence curves predicted by Li et al. (2012). The relative error of the predicted values using the PP-LB model with respect to the theoretical coexistence curve did not exceed 2% for both EOS when the EDM and improved Guo’s schemes were employed. Furthermore, by comparing the numerical performance of the so-called β-scheme for computing the Shan & Chen’s interaction force with the standard Guo’s scheme, it is found that, despite a positive impact on accuracy and reducing spurious currents, it is unstable at reduced temperatures (Tr) below 0.76, whereas the improved forcing schemes that satisfy the mechanical stability condition are stable at Tr ≥ 0.66.

16:40 - 17:00

Accuracy of SYCL implementations of Lattice Boltzmann Methods for Fluid Flow

Muite, Benson1; Mahdi Tekitek, Mohamed2

1Kichakato Kizito; 2Université de Tunis El Manar

The SYCL standard promises portability of programs on a variety of hardware including central processing units, graphical processing units and field programmable gate arrays. The speed of different operations on depends on the hardware platform chosen. The main aim of this contribution is to examine accuracy as a function of time to solution for lattice boltzmann schemes that approximate laminar incompressible two dimensional fluid flow on a single device.

17:00 - 17:20

Modeling Shrinking Biomass Pyrolysis using the REV-Scale 3-D Lattice Boltzmann Method

Cho, Yongsuk1; Kong, Song-Charng2

1Iowa State University, United States of America; 2Texas Tech University, United States of America

Biomass pyrolysis is a useful thermal decomposition method of converting low-energy value materials to fuel by breaking down a complex organic structure in an oxygen-deficient environment. It is known that the macroscopic transport equations have intrinsic limitations to accurately modeling the pyrolysis because sub-particle level phenomena alter the pyrolysis regime. For bridging the micro-scale and macro-scale phenomena, the Representative Elementary Volume (REV)-scale Lattice Boltzmann (LB) method is presented to resolve the fluid, heat, and mass transfer in both the biomass particle and the gas phase. The recently developed conjugated heat transfer LB model is adapted to model the heat transfer at the solid-gas interface. Additionally, a particle contraction method is formulated to simulate the effect of biomass shrinkage. Experiments are used to validate the three-dimensional numerical results. The predicted temperature profile and the mass loss of biomass agree well with the experimental data. The REV scale simulation shows that a linear Darcy regime governs the inside biomass flow, and the pressure build-up is detected. It was found that the variable Internal thermal conductivity is the most important parameter to accurately model the pyrolysis. The results illustrate that the biomass shrinkage accelerates particle conversion and increases the tar yield. A parametric study indicates that the increased biomass size adversely affects the overall tar yield due to the acceleration of the secondary reaction.

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