MHD控制激波诱导湍流边界层分离的机理分析

Investigation of magnetohydrodynamic control on turbulent boundary layer separation induced by shock wave

关键词:  激波边界层相互作用  MHD流动控制  小磁雷诺数  边界层分离

Key words:  SWBLI  MHD flow control  Low magnetic Reynolds number  Boundary layer separation

摘要:

为了研究磁流体动力学(Magnetohydrodynamics:MHD)加速边界层对激波-湍流边界层相互作用的影响,用高阶有限差分法求解了小磁雷诺数近似的MHD湍流方程。其中,无粘通量采用WENN格式离散、粘性通量采用Roe平均中心差分离散,时间采用半隐式推进,并采取追赶法求解。计算给出了湍流、电场、磁场和电导率等参数对边界层分离的影响,数值结果显示:在同样的逆压梯度下,湍流边界层分离能更快地趋于稳态流场,且分离区比层流小;通过施加洛仑兹力加速,边界层速度型面变得更加饱满、位移厚度减小、分离点和再附点向激波与固壁的交点靠近,分离区尺寸减小甚至最终被消除。

Abstract:

In order to study the effects of MHD accelerating boundary layer on Shock Wave–Boundary Layer Interactions (SWBLI),high order finite difference method (FDM) was used to solve the low magnetic Reynolds numbers MHD turbulent flow.In the CFD code,the inviscid and viscous flux vectors were discreted with WENN scheme and Roe-averaged central difference scheme respectively,and the explicit-implicit method was used to solve the MHD equations.The dependence of separation parameters to the turbulence,electrical field intensity,magnetic intensity and electrical conductivity of ionized air were discussed.The numerical results show that,with the same inverse pressure gradient,the time to establish steady flow for separated turbulent is shorter than that of laminar flow.The separation bubble size is smaller than that of laminar flow.With Lorenz force accelerated,the turbulent boundary layer profiles turns full,displacement thickness decreases,and the separation/reattach point moves toward the point where the incident shock impinges on the flat plate,and thus the separation bubble size is diminished or even eliminated.