The three dimensional near wake flow topology behind a blunt trai領(lǐng) edge flat plate is investigated for a Reynolds number range varying from 500 to 4.6x104 using a combination of flow visualization, numerical simulations and experiments. The secondary wake instabilities are identified using vorticity maps from CFD and performing Proper Orthogonal Decomposition (POD) on PIV data from experiments to identify the underlying dominant coherent structures. These structures are found to appear at a spanwise spacing ranging from 2.2 to 4.8. At higher Reynolds numbers the secondary wake instabilities appear to be unsteady in space and time. 德國LaVision PIV/PLIF粒子成像測速場儀