方管横向射流流动特性的DPIV实验研究

Digital particle imaging velocimetry (DPIV) was used to me as ure the transient and time-averaged flow field in the mixing region and the wak e of a square jet into crossflow at jet-to-crossflow velocity ratio (VR) o f 0.5 and 2. The phenomenon of vortex instantaneously shedding from the jet ho le was investigated, and the flow turbulence intensity was estimated. The compl ex vortical structures encountered at VR of 2 were analyzed. Compulsively o ppressed by the main flow, the jet attached to the wall at VR of 0.5, and l ifted off the wall to develope into the main flow at VR of 2. The twisted v ortices in the leeward of jet contributed to the transportation of the crossflow boundary-layer fluid into the near wake, causing intensive turbulence. Strong vortices formed near the jet hole soon broke down and dissipated, yet the weak counter-vortex pair still held in the far wake.