|Institution:||University of Illinois – Urbana-Champaign|
|Keywords:||Experimental Fluid Mechanics; Turbulence; Particle Image Velocimetry; Vortex Generators|
|Full text PDF:||http://hdl.handle.net/2142/90652|
The turbulence past thin tabs of rectangular, triangular, and ellipsoidal geometries is experimentally investigated using particle image velocimetry at Reynolds number Re=2000 and Re=12900 based on the tabs height and freestream velocity. Turbulence statistics including streamwise velocity, turbulent kinetic energy (TKE), and vortex swirling strength are obtained in the symmetry plane of each tab. The results show a strong dependency of the tab geometry on the strength of the induced vortical structures at the low Re. The turbulent flow regime at high Re promotes high shear stress and TKE production right past the tabs, where the rectangular tab induces greater mixing. The spanwise vortices from the rectangular tab have an average vortex cores radius 20% larger and nearly 30% greater circulation as compared to those from the ellipsoidal tab. Compared to the ones produced by the triangular tab, the core radius is 25% larger and the circulation is almost 50% higher. Our results also show, for the rst time, that hairpin structures are possible in triangular tabs. Finally, we conclude that geometrical singularity plays an important role in the strength of the primary vortical structures shed by the tabs.