Numerical investigation of hemolysis phenomena in the FDA nozzle benchmark : mind the extensional stresses

Abstract

In recent years, the idea of using a pump as a left ventricle assist device is being well developed by several groups. Meanwhile, one of the challenges in this field is the occurrence of biological phenomena such as hemolysis. From an engineering point of view, a solution to this problem is to provide an accurate and efficient numerical method to predict the phenomenon. Hemolysis models are typically based on equivalent scalar stress and exposure time. This paper aims to study the impact of considering extensional stresses as the main reason for hemolysis in the FDA Nozzle benchmark. The idea comes from an experimental article. First of all, flow’s hemodynamic was validated by comparing the results of normalized axial velocity in several sections with the experimental data. In this case, three different RANS models k− , k−ω and k−ω SST were employed. As expected, it is clear that the k−ω SST is the most accurate model. In the next step, hemolysis simulations performed for different equivalent stresses. In this case, the impact of scaling up the extensional stresses on predicted hemolysis is studied by adding a coefficient Cn to equivalent stress. It is concluded that by applying these new modifications the hemolysis index would be in a reliable range.