【摘要】 为了研究涡旋射流控制流动分离的物理机理,基于大涡模拟方法对涡旋射流控制下的矩形扩压器流场和射流流向涡结构的生成、发展等动力学演化过程进行了数值研究.结果表明:射流产生的流向涡将主流高动量气流带入分离区,增加了边界层内气流流动方向的动量,使流动分离得到了抑制.射流流场的涡结构主要由射流剪切层涡、马蹄涡、尾涡组成,由于速度梯度大小的变化,使得射流剪切层涡系的结构随着时间推移从涡卷演化为涡环.对于脉冲射流,在低频脉冲下,射流产生的流向涡呈涡卷结构,流动控制效果明显.在高频脉冲下,射流剪切层涡演变成间歇涡环结构,流动控制效果减弱.通过对比脉冲频率和占空比对流动控制的影响发现,占空比为0.5、频率为20Hz的脉冲射流具有较好的流动控制效果.更多还原

【Abstract】 To investigate the physical mechanism of active control of flow separation by vortex generator jets(VGJs),the flow field in a rectangle diffuser and the generation and development of vortical structures were analyzed on the basis of the large-eddy simulation(LES)method in this study.The results show that the streamwise vortices carry the high momentum into the separated region,leading to the increase in cross-stream mixing of streamwise momentum and then the suppression or delay of the separation in the diffuser.The vortical structure consists of shearlayer vortices,horseshoe vortices and wake vortices.The jet shear-layer vortices evolve from vortex loops to vortex rings with the time.For the pulsed VGJs,the streamwise vortices in the form of vortex loops control the flow separation effectively at low frequency.At high frequency,the shear-layer vortices develop into vortex rings intermittently and the flow control is suppressed.The influence of the pulsed frequency and the duty cycle on flow control was discussed.It seems that the pulsed VGJs at 20Hz may control the flow separation better when the duty cycle is 0.5.更多还原