圆形冲击射流混合过程的LIF研究-边界条件效应
We consider the effects of the mixing conditions at the nozzle, on the mixingin a circular impinging jet. Two situations are considered: the completely premixed traceror a locally injected tracer. The local instantaneous concentration field is determined byusing Planar Laser-Induced Fluorescence (PLIF) technique. The premixed injectionvariant reveals the mixing effects of the outer shear layer, while the local mixing approachhelps in understanding how to utilize the local injection for controlling the mixing of ascalar in an impinging jet. The concentration statistics and the mixing properties indicatedby concentration probability density function (PDF) with the two injection methods arepresented. The results show the well-known structural features in the turbulent impingingjet, the nature of mixing varies significantly in different regions of the jet. In the jet coreregion and the impingement region, the mixing is dominated mainly by the large-scalecoherent structure, while in the mixing layer and wall jet region, both the large-scalestructure and small scale turbulence control the mixing.