不同的扩散模型对再入体等离子体鞘电子密度分布的影响

本文研究不同的扩散模型对再入体等离子体鞘电子密度分布的影响。由于电子和离子的质量相差三个量级以上,电子的浓度扩散速度比离子大得多,引起正负电荷分离。由此产生的诱导电场又阻碍带电粒子的扩散运动。本文同时考虑这二种影响扩散的因素,得到了非平衡等离子体鞘带电粒子分布的数值解,并与准中性模型、双极扩散模型等其它三种近似模型进行了比较。计算表明:流场的大部份区域满足等离子体准中性假定,但在物面和激波附近存在电荷分离较明显的薄层,其厚度约为Debye屏蔽长度的量级。这种边界效应对中性粒子的分布影响甚微,但对带电粒子的分布则产生一定的影响。由此可以判断各种扩散模型的适用性。

The Effects of Different Diffusion Models on Electron Distribution of Plasma Sheath about Reentry Bodies

The effects of different diffusion models are studied for electron distribution of plasma sheath aboutreentry bodies. The diffusion velocity of electron due to density gradients is much larger than that ofions because the weight of the electrons is about three orders in magnitude less than that of the ions.Both the charge separation and its induced electric field exert an influence on the particle diffusion. Theelectron density distribution is obtained with numerical solution under these conditions. The results arecompared with other diffusion models such as the quasi-neutral model, ambipolar diffusion model,etc. It shows that the quasi-neutral assumption is valid in most region of the flowfield, but the chargeseparation occurs near the body surface. The dimension of the thin layer with charge separation is in thesame order of Debye shield length. The electric particle distribution is influenced somewhat by theboundary effects although the neutral moleculars and atoms are unaffected. The applicability of thesediffusion models is judged through their comparaision of the numerical solution.