平衡空气模型的流动稳定性及转捩预测

研究高超声速平板边界层考虑真实气体效应的流动稳定性问题.采用7组元化学反应平衡模型，黏度和导热系数采用混合律，同时考虑组元浓度扩散引起的能量传递，在马赫数为10~20、壁面温度为500~3500K、飞行高度为20~30.5km等条件下，对平板边界层流动的稳定性进行了分析，给出了扰动演化相对增长的N值.计算结果表明:高马赫数飞行中不稳定扰动的第3模态将与第2模态合并，共同影响转捩；高温真实气体的流动稳定性特征，随着马赫数、壁面温度、飞行高度变化的基本趋势与完全气体的基本一致；与完全气体相比，真实气体的相对增长N值包络线较小，表明高温真实气体将抑制转捩发生. 

Hydrodynamic stability and transition prediction with the chemical equilibrium gas model

For the real gas effects on the hypersonic boundary-layer flow stability of a flat plate, calculation was performed using the 7 species chemical equilibrium model, where viscosity and thermal conductivity were calculated using a mixing rule. The energy transport due to the species'' diffusion was also taken into account. The flat plat base flow was computed under the conditions of Mach number of 10-20, wall temperature of 500-3500K, and flight altitude of 20-30.5km. The flow stability was analyzed, and the N number of relative growth rate of disturbance was given. The result shows that the second and third modes of instability waves are merged under high Mach numbers, taking their tolls on transition together. With the change of Mach number, the wall temperature, flight altitude, and variation trends of real gas instability model are almost the same as the perfect gas. Compared with the perfect gas model, real gas model''s envelope line of N is lower, therefore affecting the transition prediction.