超声速弱欠膨胀冲击射流流场结构

Flowfield structure of moderately under-expanded supersonic impinging jet

关键词:  超声速冲击射流  紧致格式  大涡模拟  涡合并  激波涡干扰

Key words:  Supersonic impinging jet  Compact scheme  Large-eddy simulation  Vortex merging  Shock-vortex interaction

摘要:

为了对超声速弱欠膨胀冲击射流的流场结构细节进行研究,使用大涡模拟方法对其进行了数值模拟。利用三阶迎风和四阶对称紧致格式对无量纲化轴对称可压缩滤波N-S方程进行空间离散,时间上推进采用的是三阶精度的TVD型Rugge-kutta法。亚格子尺度模型采用的是修正Sm agorinsky涡粘性模型。通过与经典的冲击射流实验比较,证明了程序的可靠性。数值模拟得到了剪切层以及壁面射流中的涡结构和主射流中的激波结构,并且在此基础上对涡合并和板前激波和涡干扰现象进行了深入研究。发现涡合并现象主要出现在流场的上游,越往下游出现的几率越小;涡和板前激波的相互作用会引起激波位置和强度以及冲击平板上冲击区的压强的显著变化,同时也会导致涡的变形。

Abstract:

To study the details of flow structure of moderately under-expanded supersonic impinging jet,numerical simulation was conducted with large-eddy simulation.A third-order upwind compact difference and a fourth-order symmetric compact scheme were employed to discretize the nondimensional axisymmetric compressible Favre-filtered Navier-Stokes equations in space,while the third-order Runge-Kutta method with property of TVD was adopted to deal with the temporal discretization.The sub-grid scale model was formulated according to the modified Smagorinsky Eddy-viscosity model.The code was demonstrated by experimental data.The numerical simulation successfully captured the shock wave structure in the jet plume and vortex structure with different scales in the shear layer and in the wall jet.The result shows that vortex merging occurs more frequently upstream in the shear layer than that does downstream.The interaction between plate shock wave and vortex makes intensity and location of the shock wave vary greatly.It also causes the significant change of the pressure of impinging zone on the plate and vortex distortion.