Study on the spatial control of turbulent mixing enhancement using synthetic jets

采用集合平均速度、烟雾可视化和LES数值模拟等方法研究了圆形合成射流中的强湍流和强湍流混合。在距孔段一定距离处观察到强烈的混合现象，这可归因于变形涡环的有组织运动和涡环崩塌过程中纵向涡的混合作用。研究发现，在没有邻近涡圈直接干扰的情况下，涡圈崩塌的位置随着交变流行程的增大而向下游移动。在腔内孔后放置一根短同轴管，研究了其对旋涡坍缩位置的影响。研究了用收缩喷嘴代替孔板的合成射流对旋涡崩塌的影响。结果表明，这些都是合成射流增强湍流混合的空间控制方法。

The high intensity of turbulence and the strong turbulent mixing in a circular synthetic jet are studied by ensemble averaged velocities, smoke visualization and LES numerical simulation. The strong mixing is observed at some distance from the orifice, and it can be attributed to the mixing caused by the organized motion of deformed vortex rings and the longitudinal vortices in the process of vortex ring collapse. It is found that the vortex rings collapse without direct interference by neighbouring vortex rings, and the location of vortex collapse moves to downstream as the stroke of the alternating flow is increased.A short coaxial pipe was placed behind the orifice in the cavity and effect on the location of vortex collapse was studied. And the synthetic jet from a contraction nozzle instead of an orifice was studied to examine the effect on the vortex collapse. The results indicate these are possible methods of spatial control of turbulent mixing enhancement by synthetic jets.