Numerical Research On Plasma Flow Field Around Hypersonic Vehicles In Near Space

The hypersonic vehicle has great potential value in military, and it has developed rapidly in recent years. However, the plasma sheath will generate around the vehicle at a certain degree of the speed and the height, which results in an interference in the reentry target recognition as well as the communications “blackout” problem. To have a comprehensive knowledge of the impact of the plasma sheath on the reentry target recognition, and to provide an effective reference for solving the“blackout” communication problems, this paper simulates numerically the flow field distribution around the reentry hypersonic vehicles firstly, and then computes the characteristic parameters of the plasma sheath, and finally has a research on the interaction between the plasma and electromagnetic waves. The main work is summarized as follows:(1) Based on the CFD-FASTRAN software, the weakly air flow in thermochemical nonequilibrium over the two-dimensional RAM-CII and the three-dimensional sphere models are computed with the finite rate chemical reaction models. The flow field parameters are given at different Mach numbers or at different heights. The impact of the velocity and the height are respectively analyzed on the flow field distribution. The flow field distribution at the same flight situation is also computed with different thermochemical models. The results are compared to analyze the impact of different thermochemical models on distribution of the flow field around the target.(2) The research on the plasma criterion based on the flow field computation results. As characteristic parameters of the plasma sheath, the plasma frequency and the plasma collision frequency are computed. The existing several kinds of plasma collision frequency formulas are given and the proper one is chosen for the research in this paper. It is also given in the paper the distribution of the plasma frequency and the plasma collision frequency of the two-dimensional RAM-CII and the three-dimensional sphere models, whose flow fields satisfy the plasma criterion.(3) The relative permittivity of the plasma is computed according to the Drude model, and then the characteristic parameters of the incident electromagnetic waves are computed. The variation curve of the relative permittivity of the plasma and the characteristic parameters of the incident electromagnetic waves are given when one of the plasma frequency, the plasma collision frequency and the incident frequency is changing, and the impacts of these three frequencies are respectively analyzed on the propagation of electromagnetic waves.