Abstract: A hybrid grid structure DSMC method with Cartesian coordinate meshes and surface unstructured triangular cells is presented for accurately predicting the effects of RCS jet interaction with rarefied atmosphere. The adaptative algorithm ensures the molecular pairs selected in the smallest sub\|cells to enhance the space accuracy. The parallel DSMC code with a static random load balancing(BL) technique is used to simulate the lateral jet interaction flowfield of three\|dimensional plat plate model in different pressure ratio. The present BL strategies have a preferable speedup and parallel efficiency with a small number of processors. The calculated results of complicated flow structures and surface separation characters have a good agreement with a low density wind tunnel experiment. Under the condition of fixing incoming stream parameters, the separation distances and jet penetrate height in the interacting region
increase with nozzle exit pressure ratio. For more and more rarefied atmosphere, the incoming stream has less effects and jet itself affecting region extending much larger. 

Key words: Jet interaction, Flow separation, Rarefied Gas, DSMC method, Parallel computation