正激波结构与反射的蒙特卡罗模拟

MONTE CARLO SIMULATION OF THE STRUCTURE AND REFLECTION OF NORMAL SHOCK WAVES

本文用变径刚球模型(VHS)与Larsen-Borgnakke模型借助直接模拟蒙特卡罗方法模拟正激波结构与反射问题。直接模拟显示了分子间作用力幂次对激波剖面的影响,平动自由度经激波的非平衡效应,双组分气体经激波的组分分离效应,有转动自由度激发(双原子分子)气体中激波结构、传播和反射、双原子轻分子作为载体的混合气体激波结构中重气体的温度超出等。

The structure and reflexion of normal shock wave in simple monoatomic gas, diatomic gas and in gas mixtures are simulated by the direct simulation Monte Carlo method (DSMC). To simulate the intermolecular forces the variable hard sphere model (VHS) is used, and the interchange of translational energy and the internal energy is simulated by the phenomenological model of Larsen and Borgnakke. The thickness of the shock wave transition zone obtained by the VHS model for different values of the power in the intermolecular force is shown to be identical with the result obtained by the inverse power law model, provided the expressions for the mean free path correspond ing to the viscosity expressions derived for relevent models are used accordingly. Also shown is the effect of non-equilibrium in the translational degrees of freedom across shock wave in a simple monoatomic gas, i. e. the difference between the longitudinal (parallel) temperature based on the velocity component in the direction of wave progression and the transverse (perpendicular) temperature based on the velocity component in the direction perpendicular to the wave motion. For gas mixtures of two components calculations reveal the component separation effect and the effect of overshoot of the heavy component parallel temperature. In the paper the structure and the process of propagation and reflexion of normal shock wave in a diatomic gas (i, e. with coupling between the translational and rotational energies of a molecule) is also simulated, with the rotational relaxation number ZR chosen to be 5. The density profiles across the shock obtained are in good agreement with the experimental data, and the change of the parameters experienced in the reflection of the shock from a solid wall are found to be in excellent accordance with the result from the gas dynamic relations. Initiative investigations have been carried on the parellel temperature overshoot in a mixture of heavy (trace)-light (carrier, diatomic) gases. Simulation with more exact method and the analysis of the overshoot data and mechanism are underway and will be published elsewhere.