NUMERICAL COMPARISON OF SHEAR AND ELONGATIONAL STRESSES IN ROTARY VENTRICULAR ASSIST DEVICES

Introduction Ventricular Assist Devices (VADs) are becoming the gold standard treatment for end stage heart failure [1]. However, many of these post-surgical complications are related to damage to the blood components by the fluid dynamic stress in the mechanical pump. To date, most numerical models for blood damage are functions of the scalar shear stress (SSS) [2], the second invariant of the strain rate, Sij, in analogy with von Mises Stress. Since rotary VADs are assumed to exert mainly shear stress, the data for these models is obtained from Taylor-Couette flow experiments which create shear stress on the blood. However, alternative experimental data show the existence of elongational stress alongside shear stress that deform cells differently [3]. So the aim of this work was to assess the accuracy of the assumption and significance of elongational stress, in comparison with shear stress in rotary VADs using computational fluid dynamics (CFD).