Dye visualisation of inclined and skewed synthetic jets in a cross flow
Dye visualisation of inclined and skewed synthetic jets in a cross flow
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横流中倾斜和偏斜合成射流的染料可视化
作者：
S. Zhong;L. Garcillan;N. Wood
摘要在横流实验中对倾斜合成射流和倾斜合成射流进行了染料可视化，并与正常合成射流的结果进行了比较。研究了孔口出口附近的涡旋卷起过程以及结构如何发展并与下游传播的交叉流相互作用，从而了解孔口方向对合成射流行为的影响。研究了由隔膜位移和自由流速度引起的雷诺数、速度比和斯特罗哈尔数的变化对合成射流特性的影响。观察到，与正常射流相比，倾斜和倾斜射流产生的旋涡结构倾向于停留在需要最大流动控制效果的近壁面区域。在这两种情况下，在相对较低的雷诺数和速度比下，合成射流产生的主动结构表现为发夹涡，随着雷诺数和速度比的增加，发夹涡变成了远离壁面的涡环。这些发夹涡在近壁面区域持续存在，因此被认为是延迟流动分离的理想结构。
Abstract Dye visualisation of both inclined synthetic jets and skewed synthetic jets was undertaken in a cross-flow experiment and the results were compared with those of normal synthetic jets. The process of vortex roll-up near the orifice exit and how the structure develops and interacts with the cross-flow as it propagates downstream was investigated so as to obtain an understanding of the effect of orifice orientation on the behaviour of synthetic jets. The effects of varying Reynolds number, velocity ratio and Strouhal number due to changes in diaphragm displacements and freestream velocities on the characteristics of synthetic jets were also examined. It is observed that in comparison to the normal jets vortical structures produced by both inclined and skewed jets tend to stay closer to the near wall region where maximum flow control effect is required. In both cases, at a relatively low Reynolds number and velocity ratio the active structures produced by the synthetic jet appear to be hairpin vortices which turn into vortex rings that migrate away from the wall as the Reynolds number and velocity ratio increase. These hairpin vortices are persistent in the near wall region hence are believed to be desirable structures for delaying flow separation.