Study on the special Vortical structure development during flow separation control by VGJs in boundary layer of flat plate with adverse pressure gradient

Experimental and numerical studies were performed at low Reynolds number using VGJs on flat plates with adverse pressure gradient to investigate the physical mechanism of flow separation control by VGJs in boundary layers. The control effects and the statistical characteristics of different control modes were analyzed to explore the development of the large-scale coherent structure. The instantaneous flow analyses show that the hairpin or hairpin-like vortices are two classical vortical structures formed from vertical and angled VGJs in adverse pressure gradient. In downstream of angled VGJs, the additional flow structures are generated as a consequence of the hairpin-like vortices. Its formation could increase the transport of energy and mass, and then improve the dissipation effectively. In addition, the angled VGJs provides more effective separation control than the vertical VGJs.