mbnu FY2016 Annual Report 3.1.1

Figure: (Left) The cross-slot geometry where fluid is introduced from two opposite directions (blue arrows) and meet at the center of the geometry around a stagnation point. A special flow configuration allows to obtain quantitative micro-particle imaging velocimetry measurements and reveal the structure of a vortex with a simple Newtonian fluid such as water (top image) and how this vortex changes its structure and intensity with a slight addition of polymer solution (bottom image). (Right) vortex intensity ψ plotted with the Reynolds number (Re) for several fluids with increasing elasticity (El). As El is increased critical Re and vortex intensity decreases. Hysteresis is not consistent in all fluids. Experimental results are in good agreement with numerical simulations.