The development of high-efficient DSMC and its application to hypersonic Aero-optics - Prof. Zhang Bin, School of Aeronautics and Astronautics
Project:  The development of high-efficient DSMC and its application to hypersonic Aero-optics
Abstract:  We plan to use PI for two major projects. The first one is to develop high parallel efficiency Monte Carlo methods. Both the traditional DSMC and the proposed AP-DSMC are considered in this project. The second one is to study the aero-optics phenomenons in the hypersonic flow with parallel DSMC. More information about these two projects are listed as follows.

1. Improve the computational efficiency of DSMC

DSMC (direct simulation Monte Carlo) method is most widely used to simulate the rarefied flowfield. It is a statistical algorithm with a micro physical perspective, which is actually one kind of computing method to solve the Boltzmann equation. Although it has a good performance on the simulation of rarefied regimes, it is hard to expand its applications because of its unaffordable computing time. For our team, two ways are considered to accelerate DSMC computing.
① Parallelization of DSMC method
Parallelization is a common thought to accelerate the program in the computing science. However, load in each processor varies with the changing flowfield and the communication between processors is connected to the velocity of the simulated gas. On these characteristics of the DSMC method, special research on the parallelization of the DSMC method is needed. And the GPU computing is considered too.
② Parallelization of AP(asymptotic preserving)-DSMC
There is a limited parallel speedup for a definite DSMC case. So if we want to accelerate the DSMC computing, we should improve the algorithm itself. AP-DSMC is one kind of improved DSMC for near-continuum or continuum region. It computes the implicit collision terms explicitly to decrease much time of computing. Due to its difference from the traditional DSMC method, new strategies of its parallelization are needed for further speedup.

2. Research on aero-optics based on DSMC method

For those vehicles utilizing airborne optical devices, the supersonic flowfield over the optical window can cause severe optical aberrations (bore sight error, blur, distortion and jitter) of the images being detected. These aberrations are called aero-optics which are caused by the index of refraction variations in the flowfield. These indexes of refraction variations are primarily due to the mean density variations and density fluctuations. So the accurate simulation of the flowfield is needed.
There is a lot of debate about the turbulence models for NS equation. And little credible density fluctuations information can be obtained by the traditional CFD. So we are determined to use DSMC method to simulate these flowfield and high performance computing of DSMC is needed for these near-continuum cases.

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