合成射流后台阶分离流动控制的实验研究

摘要

Backward facing step flow with boundary layer separation and reattachment is a common phenomenon in engineering.The research of backward facing step flow has important theoretical significance and practical value.Backward facing step flow contains a variety of com-plex fluid mechanics,such as flow transition,flow separation,reattachment and unsteady flow. It has important academic significance in the field of fluid mechanics.The test techniques of sur-face pressure and particle image velocimetry have been applied to investigate the backward facing step turbulent separated flow control with synthetic j et.Through analysis of the pressure coeffi-cient distributions of the step wall surface,transient vortex flow structure and time-averaged flow structure,it reveals the separation flow control mechanism of synthetic j et on the backward facing step reattachment length and recirculation zone.The results show that the synthetic j et imposed on the leading edge can effectively reduce the range of the recirculation zone,the vortex structure of which is locked by the synthetic j et perturbation.In this experiment,the greater the momentum coefficient of the synthetic j et is,the better the control effect becomes.The time-av-eraged effect is:when the momentum coefficient of the synthetic jet is 0.771%,the reattachment length can be decreased by 50%.%具有边界层分离和再附的后台阶流动是工程中常见的一种复杂现象，研究后台阶绕流具有重要的理论意义和应用价值。后台阶流动包含了多种复杂的流动现象，如流动的转捩、分离、再附和非定常等流体力学基本问题。应用表面测压和粒子图像测速(PIV)对合成射流后台阶湍流分离流动控制进行了研究，通过分析后台阶壁面压力系数分布、瞬态旋涡流场结构以及时均流动结构，揭示了合成射流对后台阶再附点长度和回流区的分离流动控制机理。结果表明：在台阶前缘施加合成射流可有效减小回流区范围，回流区涡结构被施加的合成射流扰动“锁定”。在实验状态下，合成射流的动量系数越大，控制效果越好。从时均效果看，当合成射流的动量系数为0.771%时，可使再附点长度减小50%。