平面撞击流的直接数值模拟

Direct Numerical Simulation of Plain Opposed Jet

撞击流因其独特的流场性质在工业过程中有着广泛的应用。本文采用基于有限差分格式的直接数值模拟程序首先对Re=2500的平面射流进了模拟,得到的结果与实验值相当吻合,验证了程序的有效性;然后对喷嘴间距比L/h=10(L为喷嘴间距,h为喷嘴高度)的受限空间内平面撞击流进行了模拟,发现撞击流中轴向射流和径向射流的剪切层出现了和平面射流类似的涡卷起和配对的现象,并且平均速度场中出现了大尺度的回流区。模拟再现了实验中的偏斜振荡和轴向偏移现象,其中轴向偏移显著地增加了撞击区的轴向脉动。

Opposed jet is widely used in industrial process due to its unique flow characteristic. Direct numerical simulation（DNS） based on finite differences method was used to investigate a plain opposed-jets. First of all, a plain jet at Re=2500 was tested. The results fit quite well with the experiment data, which can validate the code. Then plain opposed-jets with nozzle spacing of L/h=lO （L is the distance between two nozzles, h is the height of the nozzle） was simulated, the results show that vortex rolling-up and pairing in the axial jet and radial jet of the opposed-jets is similar to that of the plain jet. Large scale circulation reflux districts exist in the averaged velocity field. The results also capture the evident phenomenon of deflective oscillation and axial skewing, which is similar to that observed in experiments. The axial skewing can significantly increase the axial fluctuating velocity in the impinging zone.