二维高超声速后台阶表面传热特性实验研究

高超声速后台阶流动是大气层内高速飞行器发动机设计、表面热防护以及高超声速拦截器红外成像窗口气动光学效应校正等诸多先进高超声速技术研发过程中所涉及的一类基础流动问题. 研究高超声速后台阶流动特性对有效提升飞行器综合性能, 进一步掌握高超声速流动机理具有重大基础 意义. 本文以二维高超声速后台阶流动为研究对象, 在KD-01高超声速激波风洞中测量了二维后台阶模型表面传热系数和表面静压, 并将实测台阶下游表面传热系数分布同采用高超声速边界层理论所得估计值进行了比较. 为进一步验证实验结果, 使用NPLS技术测量了其中一种实验状态下台阶周围流动结构. 研究发现, 对于二维高超声速后台阶流动, 台阶下游表面传热分布受台阶处边界层外缘流动特性的直接影响; 在台阶下游分离区和再附区内, 气体黏性占主导作用; 在台阶下游远场区域, 边界层流动特性趋同于平板边界层; 下游边界层基本结构取决于台阶处边界层相对厚度. 对高超声速后台阶流动, 若使用数值模拟方法研究气动热问题, 应当使用湍流模型.

Experimental investigation on surface heat transfer characteristics of hypersonic two-dimensional rearward-facing step flow

Hypersonic rearward-facing step flow is one of the basic flow problems in the design of engine for endo-atmospheric hypersonic vehicle, including thermal protection, and aero-optical correction for infrared imaging window of hypersonic interceptors, etc. To know the characteristics of hypersonic rearward-facing step flow is of vital importance in improving the performances of vehicles, and understanding the basis of the flow. This paper investigates the characteristics of a two-dimensional hypersonic rearward-facing step flow, measures the surface heat transfer coefficient and the surface static pressure downstream the step, and compares the results with the values predicted using the hypersonic boundary layer theory. And the results are demonstrated by the flow structure visualization using NPLS (nano-based planar laser scattering) technique. It is concluded that for the hypersonic two-dimensional rearward-facing step flow, the surface heat transfer distribution can be determined directly by the boundary layer edge parameters at the step; and the viscous effect dominates the flow characteristic in the separation and reattachment region; whole in the far-field region downstream the step, the heat transfer coefficient approaches an asymptotic value that may be equal to the turbulent flat plate value. Furthermore, the boundary layer structure may depend on the ratio of boundary layer thickness to the height of step. It is concluded that, when studying the problem of hypersonic rearward-facing step using CFD (computational fluid dynamics) technology, choosing an appropriate turbulent model is needed.