摘要
研究了高超声速平板边界层因壁温时变引发的非定常气动热环境特征及机理.通过近似解析和数值模拟两种手段,得到了壁面热流随时间变化的完整过程.解析手段求解非定常可压缩边界层方程,将非定常响应表达成稳态解加上摄动级数的形式,在初始和最终稳态邻域分别求解,在适当的位置进行拼接,从而得到整个时间域上的解.在满足解析解假设的区域,数值结果与解析结果吻合较好,证明了所使用方法的可靠性.结果表明,非定常响应有两点显著特征:在壁温突然增加后短时间内,壁面热流方向改变,热边界层剖面在壁面附近出现了另一个拐点.这种新的剖面形状是典型的非定常特征.但是,高超声速情况下此种非定常响应存在的时间却很短,在考虑长时间气动加热的情况下,若只存在壁面温度时变的诱因.可以忽略流动中的非定常过程,当作准定常情况来处理.
The characteristics and mechanism of the tmsteady aerodynamic heating of a transient hypersonic boundary layer caused by a sudden change in surface temperature was studied, the complete time history of wall heat flux was presented by both analytical and numerical approaches. With analytical methods, the unsteady compressible boundary layer equation was solved. In the neighborhoods of initial and final steady state, the transient response can be expressed by a steady-state solution plus a perturbation series, respectively. By patching these two solutions, the complete solution in the entire time domain was achieved. In the region where the assumptions of analytical approach are satisfied, the numerical and analytical results were matched well, proving the reliability of the methods. The restilt showed two distinct features of the unsteady response. In the short period just after a sudden increase in the wall temperature, the direction of the wall heat flux reverted, a new inflexion near the wall arose in the profile of the thermal boundary layer, which is a typical tmsteady characteristic. However, these unsteady responses only exist in a very short period in hypersonic flows, which means that, in a long-term aerodynamic heating process considering only unsteady surface temperature, the unsteady characteristics of the flow can be ignored and the traditional quasi-steady aerodynamic heating prediction methods are still valid.
出处
《应用数学和力学》
CSCD
北大核心
2009年第2期160-170,共11页
Applied Mathematics and Mechanics
基金
国家自然科学基金资助项目(90716011)
关键词
非定常气动加热
高超声速
壁温时变
近似解析
数值模拟
unsteady aerodynamic heating
hypersonic
unsteady surface temperature
approximate analysis
numerical simulation
