烧蚀后的C-SiC隔离段内流场精细测量试验

Fine Measurement Experiment of Internal Flow Field in Ablated C-SiC Isolator

关键词:  隔离段  粗糙度  激波串  流场  复合材料  烧蚀  附面层

Key words:  Isolator  Roughness  Shock train  Flow field  Composite material  Ablation  Bourdary layer

摘要:

为了获得极度粗糙内壁面对激波串流动特性的影响规律，通过基于纳米粒子示踪的平面激光散射技术和高频动态压力测量技术测量了Ma2来流下烧蚀后的C-SiC隔离段中激波串流场结构，获得了激波串初始激波形态、激波后附面层发展形态以及激波串动态特性。结果表明，烧蚀后的C-SiC隔离段中激波串结构与光滑不锈钢隔离段相似。但是极度粗糙的内壁面深刻影响了近壁区流动，附面层增厚效应非常明显。前者激波串内的附面层比后者厚约50%，前者激波分叉点比后者更接近唇口约30%。极度粗糙的内壁面也提高了附面层的分形维数，加剧了拟序结构的破碎程度。烧蚀后的C-SiC隔离段中附面层的分形维数在1.548~1.649，比光滑不锈钢隔离段高6.7%~8.9%。烧蚀后的C-SiC隔离段极度粗糙内壁面对激波串振荡频率几乎没有影响。激波串前传过程中的振荡频率约20Hz。

Abstract:

In order to obtain the influence rule of the extremely rough inner wall on the flow characteristics of the shock train， the flow structure of the shock train in the ablated C-SiC isolator under Mach number 2 flow was measured by nanoparticle-tracer planar laser scattering technology and dynamic pressure measurement technology， the initial shock wave shape of the shock train， the development pattern of the boundary layer after shock wave and dynamic characteristics of the shock train were obtained. The results show that the flow structure of the shock train in the ablated C-SiC isolator is similar to the isolator with stainless steel materials. But the extremely rough inner wall profoundly affects the flow in the near wall area， and the thickening effect of the boundary layer is very obvious.The former’s boundary layer in the shock train is about 50% thicker than the latter， and the former’s shock bifurcation point is 30% closer to the lip than the latter. The extremely rough inner wall also increases the the fractal dimension of the boundary layer， and exacerbates the fragmentation of the pseudo-sequence structure.The fractal dimension of the boundary layer in the ablated C-SiC isolator is 1.548~1.649， and is 6.7%~8.9% higher than that of the stainless steel isolator. Extremely rough walls of the ablated C-SiC isolator have almost no effect on the oscillation frequency of the shock train. The oscillation frequency is about 20Hz when the shock train travels forward.