论文标题
超声尖端分离的不稳定
Unsteadiness in hypersonic leading-edge separation
论文作者
论文摘要
研究高超声前沿分离是为了理解与新建造的Hypersonic Ludwieg Tunnel（HLT）中新建的Hypersonic Ludwieg Tunnel（HLT）中的自由式雷诺数（$ 1.66 \ times 10^5 \ leq req re_d \ leq 5.85 \ times 10^5 $）的不同相关的不稳定。基本直径的轴对称平面圆柱体$ d = 35 $ mm装有不同细度的突出（$ d/d = 0.1,0.2,0.2,0.2,0.26,0.34 $ in $ l/d = 1.4 $）和细长（$ l/d/d = 0.7,1.4,1.4,1.9 $ d = 0.2 = 0.2 = 0.2 $ d = 0.2 = 0.2 = 0.2 $ - d = 0.2 = 0.2 = 2强度。使用Schlieren成像，平面激光雷利散射和不稳定的压力测量进行定性和定量评估。一种称为脉动的著名对抛冲击运动，被观察到$ re_d $变化。较短的突出长度（$ l/d = 0.7 $）产生的压力载荷比长度更长的情况高四个阶。存在关键的分离长度（$ l/d \ geq 1.4 $），超过该分离的剪切层旅行以湍流，并随着$ re_d $的增加而引入再循环区域的波动。分离的湍流剪切层的效果会被订单抑制，前提是重新介绍角度通过增加细度比（$ d/d = 0.4 $）。还有一个关键的几何参数（$ l/d = 1，d/d = 0.2 $），为此，不稳定的模式基于上游波动在连续运行之间切换。从对瑞利散射图像的模态分析中，驱动拍打的前四个主要模式被识别为译本拍打，弯曲的拍打，大和小规模的脱落。
Hypersonic leading-edge separation is studied towards understanding the varying shock-related unsteadiness with freestream Reynolds number ($1.66 \times 10^5 \leq Re_D \leq 5.85 \times 10^5$) in the newly constructed hypersonic Ludwieg tunnel (HLT) at a freestream design Mach number of $M_\infty=6.0$. An axisymmetric flat-face cylinder of base body diameter $D=35$ mm is fitted with protrusions of different fineness ($d/D=0.1,0.2,0.26,0.34$ at $L/D=1.4$) and slenderness ($L/D=0.7,1,1.4,1.9$ at $d/D=0.2$) ratio to induce a wide range of leading-edge separation intensities. Qualitative and quantitative assessments are made using schlieren imaging, planar laser Rayleigh scattering, and unsteady pressure measurements. A well-known to-and-fro shock motion called pulsation and a flapping shock-shear layer oscillation is observed as $Re_D$ changes. A shorter protrusion length ($L/D=0.7$) produces a pressure loading that is four orders higher than the cases with longer protrusion lengths. There exists a critical separation length ($L/D \geq 1.4$) beyond which the separated shear layer trips to turbulence and introduces fluctuations in the recirculation region as $Re_D$ increases. The effect of the separated turbulent shear layer is dampened by an order provided the reattachment angle is shallow by increasing the fineness ratio ($d/D=0.4$). There also exists a critical geometrical parameter ($L/D=1, d/D=0.2$) for which the unsteady modes switch between successive runs based on the upstream fluctuations. From the modal analysis of the Rayleigh scattering images, the first four dominant modes that drive flapping are identified as translatory flapping, sinuous flapping, large and small-scale shedding.
