矩形扩压通道内流动控制的实验与数值研究

Experimental and Numerical Study on Flow Separation Control in Rectangle Diffuser

采用粒子成像测速技术和大涡模拟方法对带有涡旋射流的矩形扩压器分离控制的流场进行了实验和数值分析,数值计算结果与实验数据吻合良好。通过分析实验和计算得到相关截面速度和涡量分布,讨论了涡旋射流的二维涡结构;同时应用三维涡识别技术获得了射流产生各种涡旋结构的流动形态,重点研究射流流向涡结构的生成、发展等动力学演化过程。结果表明:射流剪切层涡系的结构随着时间推移从涡卷演化为了涡环;射流孔口前缘的马蹄涡系具有较强的稳定性,反向涡对具有明显的时均特性。此外还通过对比射流控制前后扩压器表面压力系数、分离区长度、扩张段流动形态及观测点功率谱分析等多种方式探讨了射流控制流动分离的控制效果,并指出射流在下游远场形成的纵向涡旋将主流流场边界层外的高能流体卷入到边界层内,增加了边界层内部的流动能量,从而延缓或抑制了流动分离。

To investigate the mechanism of active control for flow separation in rectangle diffuser by vortex generator jets （VGJs） method,numerical analysis with large-eddy simulation and experimental measurement by particle image velocimetry （PIV） were carried out for the flow field.The numerical results show good agreement with experimental data.The two dimensional vortical structure was discussed in detail via the analysis of their velocity and vorticity distribution.Based on the three dimensional identification of vortex,several vortical structure,with emphasis on the dynamic process of its generation and development,was also discussed.The results show that the jet shear-layer vortices evolved from vortex loops to vortex rings as time go on.Horseshoe vortices wrap around the jet nozzle have the strong stability.The counter-rotating vortex pair has mean-flow definition although they may also have unsteady components.Moreover,to investigate the effect of VGJs on separation control,the surface pressure coefficient,the length of separation zone,the flow characteristics in diffuser and pressure power spectra were compared with and without VGJs.It revealed the longitudinal vortices generate at the downstream of jet increase cross-stream mixing of streamwise momentum and then suppress or delay the separation in diffuser.