Conference Agenda

Overview and details of the sessions of this conference. Please select a date or location to show only sessions at that day or location. Please select a single session for detailed view (with abstracts and downloads if available).

Please note that all times are shown in the time zone of the conference. The current conference time is: 18th Aug 2022, 10:44:14pm CEST

 
 
Session Overview
Session
Thermal and Compressible Flows etc.
Time:
Wednesday, 29/June/2022:
3:40pm - 5:00pm

Session Chair: Ezeddine Sediki, Faculty of Science of Tunis- University of Tunis El Manar
Location: Michel Crépeau's Lecture Hall, Pôle Communication, La Rochelle University

Pôle Communication Multimédia Reseaux, La Rochelle University, 44 Avenue Albert Einstein, La Rochelle.

External Resource:
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Presentations
3:40pm - 4:00pm

Fluid-Structure Interaction coupled to transport phenomena: Biomedical applications

Kaoui, Badr

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

We propose numerical schemes to tackle problems that involve fluid-structure interaction coupled to transport phenomena. We use the lattice Boltzmann method to compute fluid flow as well as advection-diffusion-reaction of chemical entities. We compute structure dynamics using the spring model and we couple it to transport phenomena using the immersed boundary method. We propose also an algorithm to implement unsteady jump boundary condition to deal with mass transfer across moving deformable boundaries that exhibit resistance and discontinuity in concentration. As applications, we show briefly results obtained for drug delivery from particles subjected to flow, performance of an artificial pancreas-on-chip, and biochemically induced oscillations of the lymphatic vessels walls.



4:00pm - 4:20pm

NUMERICAL SIMULATIONS OF CAPSULE DEFORMATION IN A COMBINED SHEAR FLOW AND DC ELECTRIC FIELD

Peng, Yan; Armstrong, Charles

Old Dominion University, United States of America

In this work a numerical method for fully three dimensional simulations of capsules in the electrohydrodynamic regime is proposed. A quasi-steady dual time-stepping scheme allows for iterative computation of the capsule's fluid velocity using the multigrid lattice Boltzmann method at each time step. The capsule's elasticity is computed using a linear finite element method and the membrane's bending resistance is computed from the Helfrich bending energy. The immersed interface method (IIM) is used to compute the electric field arising due to the electrical properties of the interior fluid, exterior fluid, and the membrane. The fluid structure interaction is facilitated through the immersed boundary method (IBM), which is coupled to the IIM through least squares interpolation between the control points of the IIM and the Lagrangian nodes of the IBM. The method is validated by comparing the numerical results to analytical solutions and previously published studies. The method is then used to study the deformation of capsules in a combined shear flow and DC electric field for various membrane conductances, membrane capacitances, and conductivity ratios. For nonconducting membranes the interaction between the distribution of the electric forces and the capsule inclination angle due to the shear flow result in complex equilibrium dynamics not reported for neutral capsules.



4:20pm - 4:40pm

Simulations of boiling flow on the heterogeneous surface of a nuclear reactor fuel assembly system

Mokos, Athanasios1; Patel, Ravi Ajitbhai2; Peng, Haonan1,3; Karalis, Konstantinos3; Churakov, Sergey1,3; Prasianakis, Nikolaos1

1Laboratory for Waste Management, Paul Scherrer Institute, Switzerland; 2Institute of Concrete Structures and Building Materials, Karlsruhe Institute of Technology, Germany; 3Institute of Geological Sciences, University of Bern, Switzerland

Despite the extensive use of water as a coolant in nuclear reactors (both boiling and pressurized) as well as other industrial applications, the heterogeneous nucleate boiling mechanism controlling evaporation and condensation is still not sufficiently understood. This is particularly important within the fuel assembly systems, where the boiling on the surface leads to inefficient heat transfer and increased thermal fatigue.

A recent molecular dynamics approach investigated the effect of different crystallographic orientations of zirconia (ZrO2) [1], the material used for the fuel cladding, identifying different contact angles for each. These results have been incorporated in a multiphase non-isothermal LB simulation, using a single-relaxation-time scheme to retrieve the momentum equation and a two-relaxation-time scheme for the energy equation [2].

The simulations investigate the behavior of vapour bubbles on and above rough zirconia surfaces, with emphasis on the effect of the contact angle. The generation of bubbles from small orifices, bubble coalescence and nucleation are investigated above rough surfaces. The results show a reduction of bubble waiting periods as the heating rate increases and faster bubble departure in hydrophilic surfaces. Initial simulations are conducted in 2D. For the acceleration of simulations in 3D, a parallel LB GPU code is being developed. Moreover, additional LB multiphase models are being incorporated.

1. Karalis, K., et al., Deciphering The Molecular Mechanism Of Water Boiling At Heterogeneous Interfaces. Scientific Reports, 2021. 11(19858).

2. Patel, R.A., et al., A three-dimensional lattice Boltzmann method based reactive transport model to simulate changes in cement paste microstructure due to calcium leaching. Construction and Building Materials, 2018. 166: p. 158-170.



4:40pm - 5:00pm

Comparison of Lattice Boltzmann Method Collision Operators for Simulation of Transient Thermal Conditions in Data Center

Sjölund, Johannes1,2; Summers, Jon1,2

1RISE Research Institutes of Sweden, Sweden; 2Luleå University of Technology, Sweden

This study evaluates three different lattice Boltzmann method-based (LBM) large-eddy simulations (LES) applied to thermal flow inside a data center. Thermal fields from the simulation are compared against time-series data recorded during operation of a real-world slab-floor data center containing 360 servers and thermal management using computer room air handling (CRAH) units.

The three LBM collision operators evaluated for velocity fields were single-relaxation time (SRT) Bhatnagar-Gross-Krook (BGK), two-relaxation time (TRT) both on a D3Q19 lattice, and multiple-relaxation time (MRT) on a D3Q27 lattice. The velocity fields were coupled to an SRT D3Q7 temperature field through advection and natural convection using Boussinesq approximation.

Good agreement between measured and simulated temperatures were seen in areas of low turbulence. The more complex operators were found to be more stable at higher Reynolds numbers and allow for greater fine-tuning of turbulence models. Although, in the present simulation differences in accuracy between them were minimal while computational performance was affected.



 
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