MULTISCALE SIMULATION FOR FLUID FLOW AND HEAT TRANSFER PROBLEMS: A BRIEF REVIEW AND FURTHER RESEARCH NEEDS
This keynote presentation includes following four parts. In Part 1, the question of "What is the multiscale simulation(MSS)?" is answered. System or process which covers several geometric or time scales is called multiscale problem. From numerical simulation viewpoint, the multiscale problems in thermo-fluid science and engineering may be divided into two categories: multiscale process and multiscale system. The transport phenomena in a PEMFC and cooling of a data center are, respectively, the examples of the multiscale process and multiscale system. In Part 2, how to do the MSS is presented. For the multiscale process there are two numerical approaches. One is solving regionally and coupled at the interface. Numerical methods of different scales are adopted in different regions of the same problem, and at the interface of two regions, the solutions from the two regions are coupled to ensure the continuity in dependent variables and their first order derivative. The other approach is the upscale method, in which the mesoscale or microscale method is used to predict some parameters and they are adopted in the macroscale simulation. In the 3rd part, "Why should we adopt the MSS?" is answered. There are two reasons. One reason is that computational resource can be greatly saved by the MSS. The other reason is that with the MSS one can find or reveal some new results which can not be obtained by single scale method. Examples will be provided. Finally, the further research needs in the MSS are suggested.