Experimental investigation of the fluid dynamics inside any blood pumping device is necessary for several reasons. First, improved understanding about the flow near the walls of a blood pump is important since thrombus formation (blood clotting) may occur when the shear stress is nearly zero. If the shear stress is in the opposite direction to the main body of the flow, a region of stagnation or recirculation is indicated, which may also lead to thrombosis. A second problem of importance to blood flows is hemolysis, the destruction of red blood cells. Hemolysis can be caused by high shear stresses imposed on the blood cells by the flow. Since hemolysis is a function of at least shear stress and residence time, an understanding of how these two variables are coupled is desirable. Third, an accurate measurement of wall shear stress and flow patterns is also necessary to validate computational fluid dynamics (CFD) predictions in the design of blood pumps. It is widely known that improper meshing of the numerical pump model, the use of an incorrect turbulence model, or errors in choosing boundary conditions can lead to a model that is in contradiction to experimental results. Quantitative oil streaking has been implemented in order to measure the wall shear stresses in the pump and supply the necessary information needed to ensure a good pump design.

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