高超声速三维边界层横流转捩的数值研究  

Numerical study on cross-flow transition in three-dimensional hypersonic boundary layers

作　　者：韩宇峰 马绍贤 苏彩虹 HAN Yufeng;MA Shaoxian;SU Caihong(The Laboratory of High Speed Aerodynamics,School of Mechanical Engineering,Tianjin University,Tianjin 300072,China)

机构地区：[1]天津大学机械学院高速空气动力学研究室

出　　处：《空气动力学学报》2019年第4期522-529,共8页Acta Aerodynamica Sinica

基　　金：国家自然科学基金项目(11472188)

摘　　要：横流失稳是高超声速三维边界层转捩的主要机制。然而到目前为止,由横流失稳导致高超声速三维边界层转捩的数值研究还不多见。本文采用直接数值模拟方法计算了马赫数6、后掠角45°钝板边界层中定常横流涡的演化,在此基础上引入高频二次失稳模态,计算了二次失稳模态的非线性演化,直至湍流发生。计算结果表明:横流定常涡的非线性作用引起平均流修正,可使壁面摩擦系数曲线有一定程度的抬升。而高频二次失稳波的增长导致低频及定常扰动快速增长,促使壁面摩擦系数急剧抬升,同时饱和横流涡结构破碎,最终触发转捩发生。Cross-flow instability is the main transition mechanism in three-dimensional hypersonic boundary layers.However,up to now,there are few numerical investigations on the breakdown process to turbulence for hypersonic boundary layers induced by cross-flow instability.In this paper,the boundary-layer transition is investigated for a blunted flat plate with Mach number 6 and sweep angle of 45 deg.Direct numerical simulations are performed for the linear and nonlinear evolution of stationary cross-flow vortex,as well as the development of the second instability waves on the saturated mean flow,and the transition to turbulence.The results show that the modification of the mean flow caused by the nonlinear effect of the stationary vortices can lead to the rise of the wall friction coefficient curve.However,without introducing the secondary instability waves,the wall friction coefficient stay constant and cannot rise to the value of turbulence level.The introduced high frequency secondary instability waves grow dramatically,and the low frequency disturbances,including stationary ones,which are generated due to the nonlinear interaction,amplify significantly as well.As a result,the mean flow is modified rapidly,leading to a steep rise in the wall friction coefficient.Following that,the saturated crossflow vortex structure breaks down,and the flow transitions to turbulence.

关 键 词：高超声速边界层 横流 转捩 二次失稳 

分 类 号：O357.4[理学—流体力学]