报告人: 徐昆教授 香港科技大学
时 间：2011年10月21日 16:30
摘 要: With discretized particle velocity space, a unified gas-kinetic scheme for entire Knudsen number flows is constructed based on the approximate Boltzmann equation. In comparison with many existing kinetic schemes for the Boltzmann equation, the current method has no difficulty to get accurate solution in the continuum flow regime with the time step being much larger than the particle collision time, and the rarefied flow solution. The unified scheme is an extension of the gas-kinetic BGK-NS scheme from the continuum to the rarefied flows with the discretization of particle velocity space. The success of the method is due to the un-splitting treatment for the particle transport and collision in the evaluation of local solution of the gas distribution function. For these operator splitting methods which solve the transport and collision separately, such as discrete ordinate method (DOM), it is usually required that the time step is less than the particle collision time, which basically makes these methods useless in the continuum flow regime, especially in the high Reynolds case. The unified gas-kinetic scheme can simulate the flow accurately in the whole flow regime from the continuum Navier-Stokes solutions to the free molecule flow. The reason for the success of the unified scheme is that it is a multi-scale method. The update of microscopic gas distribution function is coupled with the update of macroscopic flow variables.