流体中PIV检测方案(粒子图像测速)

Numerical simulations of particle image velocimetry (PIV) experiments con- ducted with vortex generating jets (VGJs) on a °at plate, at a Reynolds number based on plate length of 50,000, were performed for three °ow conditions using a time-accurate hybrid Navier-Stokes solver. Time-averaged steady blowing of angled jets, subjected to a zero pressure gradient, yielded excellent agreement with the PIV data in terms of vortex formation and strength. Observed °ow features include pri- mary and secondary vortices, where the primary vortex eventually dominates the downstream region. A shell wall structure, created by smaller vortical structures sur- rounding the developing vortices, was also observed. A pulsed jet in a zero pressure gradient was then initialized from a no-control case. A qualitative comparison be- tween averaged experimental and instantaneous numerical results was performed with good agreement in terms of the convected size and distance of the wake. Analysis of the instantaneous numerical °ow ¯eld agreed well with various °ow visualization experiments describing the formation of \kidney" vortices. Various indicators point to the production of a primary vortex by the reduced mass °ow of the pulsed jet. Finally, an adverse pressure gradient was applied, inducing a laminar separation zone on the plate. A pulsed angled jet induced strong spanwise vortices in the separated shear layer which appear to weaken the separation zone and allow the bulk jet °uid to °ush the remaining low-momentum °uid out of the domain. It is reasonable to assume that reduced blowing ratios and duty cycles would produce similar shear layer vortices and comparable loss reductions. In°uences of both turbulent transition and dominant vortical structures were observed, though the spanwise shear layer vortices appear to be critical to the laminar separation reduction scenarios observed in this study.