Numerical Simulation Of Plasma Plume With Unsteady Chemical Reaction Based On DSMC/PIC Method

The numerical method of continuous flow calculation is no longer applicable when the plasma plumes diffuse into rarefied environment,the components and collision of the plumes are complex,chemical reactions will occur,and the particles collide with the wall surface when moving to the wall.Some of the particles are reflected,and some of the particles react on the wall.Moreover,the action of charged ions under the electric field is complicated,which leads to more complicated chemical reactions and interactions on the wall.In this paper,the DSMC/PIC hybrid algorithm is used to study the diffusion and evolution process of plasma plumes.The main research contents are as follows:Neutral particle dissociation-recombination reactions,charge exchange reactions between neutral particles with charged ions,and chemical reaction on the wall are studid.Charged ions participate in chemical reactions,but do not consider the effects of electric and magnetic fields.The research shows that the chemical reactions on the wall has the greatest influence on the spatiotemporal distribution and transport characteristics of the flow field,and the charge exchange reactions has less influence.The dissociation-recombination reaction of neutral particles has a significant influence on the spatiotemporal distribution of molecular hydrogen H₂ and atomic hydrogen H in the flow field,has little effect on atomic metal X,ion H₂⁺and ion H⁺that do not participate in chemical reactions.The DSMC/PIC hybrid algorithm was developed based on the DSMC program of the research group.The PIC module was added to the DSMC module to solve the electric field by the Poisson equation.The atomic hydrogen H and ion H⁺were injected through the hole,and simulated by DSMC,PIC and DSMC/PIC hybrid algorithms.The calculation results were compared and analyzed,the results showed that the number density and temperature of atomic hydrogen H and ion H⁺gradually decreased along the axis.DSMC parallel algorithm is researched.The parallel algorithm is implemented based on MPI communication.The parallel algorithm is tested on the workstation.The test results show that the serial calculation results are agreement with the parallel calculation results.The acceleration ratio can reach 8 at 32 nodes,and the calculation efficiency is greatly improved.However,it is also found that the parallel algorithm load balance is poor and needs to be further optimized.