【作者】 胡延超； 毕卫涛； 李师尧； 佘振苏；

【Author】 Yanchao Hu;Weitao Bi;Shiyao Li;Zhensu She;State Key Laboratory for Turbulence and Complex Systems,College of Engineering,Peking University;

【机构】 北京大学工学院,湍流与复杂系统国家重点实验室；

【摘要】 湍流边界层研究的挑战之一是理解非平衡边界层的恢复过程,而激波边界层干扰就是湍流边界层出现非平衡特性的常见因素。经典边界层理论不能刻画这种强逆压梯度边界层流动,因而仍无令人满意的计算模型。本文报告了压缩拐角直接数值模拟的计算结果,揭示了恢复边界层中脉动场的激发对雷诺应力和湍热流具有明显的增强作用。一个重要的发现是,剩余雷诺应力和湍热流在壁面法向方向服从Beta分布。其形式是两个空间距离幂次律的乘积,两个距离分别为空间某点到壁面的距离和到边界层边缘的距离。另外,剩余雷诺应力和湍热流沿着流向方向也以幂次律形式衰减。这说明恢复边界层复杂的非平衡流动中仍然存在着拓展的对称性。Beta分布可以为发展湍流模型提供重要信息。更多还原

【Abstract】 A challenge in the study of turbulent boundary layers(TBLs) is to understand the non-equilibrium relaxation process after separation and reattachment due to shock-wave/boundary-layer interaction.The classical boundary layer theory cannot deal with the strong adverse pressure gradient,and hence,the computational modeling of this process remains inaccurate.Here,we report the direct numerical simulation results of the relaxation TBL behind a compression ramp,which reveal the presence of intense largescale eddies,with significantly enhanced Reynolds stress and turbulent heat flux.A crucial finding is that the wall-normal profiles of the excess Reynolds stress and turbulent heat flux obey a Beta distribution,which is a product of two power laws with respect to the wall-normal distances from the wall and from the boundary layer edge.In addition,the streamwise decays of the excess Reynolds stress and turbulent heat flux also exhibit power laws with respect to the streamwise distance from the corner of the compression ramp.These results suggest that the relaxation TBL obeys the dilation symmetry,which is a specific form of self-organization in this complex non-equilibrium flow.The Betadistribution yields important hints for the development of a turbulence model.更多还原