Dr. Toshio Tagawa
Department of Aeronautics and Astronautics
Tokyo Metropolitan University
Toshio Tagawa is an Associate Professor at Department of Aeronautics and Astronautics, Tokyo Metropolitan University, Japan. He received Dr. Eng. in 1997 from Kyushu University. He continued to study and work in the laboratory of Professor Hiroyuki Ozoe as a Research Associate and then moved to Tokyo Metropolitan University in 2005. He received the Award for Scientific Contribution in 2003 from the Heat Transfer Society of Japan. He has been engaged in the study of computational fluid dynamics, magnetohydrodynamic flows and heat transfer in natural convection and two-phase flows, and currently jointly with Professor Kewei Song at Lanzhou Jiatong University.
Title: A Lattice Boltzmann Method for multiphase flows with heat transfer
Abstract: In this study, we developed a numerical code based on the Lattice Boltzmann Method (LBM) to compute the gas-liquid two-phase flow for a high-density ratio with phase change. When analyzing gas-liquid two-phase flow with phase change, it is usually to solve the pressure Poisson equation by an iterative method. However, when analyzing gas-liquid two-phase flow with phase change by that method, the iterative calculation time of the pressure Poisson equation is a problem because of high density ratio, large-scale analysis and so on. Therefore, in this study, we adopted LBM, which is a weak compression solution and does not require solving the pressure Poisson equation. However, when analyzing gas-liquid two-phase flow with phase change by LBM, numerical stability becomes a problem under the conditions such as high density ratio and violent flow. Therefore, we expanded the gas-liquid two-phase flow analysis method by Velocity based LBM, which has excellent numerical stability, and developed a calculation code that can analyze the gas-liquid two-phase flow with phase change. The governing equations are the mass conservation equation, the momentum equations, the energy equation, and the Conservative-Allen-Cahn (C-A-C) equation, in which the phase change is introduced as the source term and the temperature change of the physical property value is ignored. Using the developed code, we analyzed the Stefan problem and obtained results that were in good agreement with the analytical solution. We also tried to reproduce nuclear boiling by adding a microlayer model, conjugated heat transfer, and nuclear generation model to the calculation code. We obtained results that are in good agreement with an experiment regarding the bubble separation cycle, separation diameter, heat transfer coefficient, and so on. Furthermore, we succeeded in reproducing nuclear boiling with a high density ratio and violent bubbles. In addition, it was confirmed that this calculation code can efficiently analyze the gas-liquid two-phase flow with phase change.