中文摘要：

针对PIC模拟程序中性粒子状态的描述问题，建立了等离子体中多元多相中性气体的流体模型，研究了与其相关的边界条件的处理方法，采用二阶精度的Beam—Warming差分格式进行数值方法，成功地应用于气体绝热点源扩散过程的数值运算，所得结果与理论取得很好的一致。该模型将用于扩充PIC粒子模拟程序对中性粒子状态的描述。

英文摘要：

To deal with the lack of detailed depiction of neutral gas in PIC simulation, the paper presents a two - dimensional model of multi - element and multi - phase neutral gas to depict explicitly the fields of neutral gas in plasma region. Numerical methods of solving the proposed equations as well as various boundary conditions are put forward. The above model and method are applied to the simulation of adiabatic gas diffusion. The results obtained well accord with the theory. The model can be used in improving PIC simulation programs.