Effect of turbulent inlet conditions on the prediction of flow field and hemolysis in the FDA ideal medical device

Abstract

Hemolysis is one of the most important issues of blood contacting artificial organs. Computational fluid dynamics, in conjunction with hemolysis models, has been widely used to predict the flow field and hemolysis during the development phase of these devices. It is widely accepted that hemolysis is related to flow field parameters, such as stress and energy dissipation. It is known that inlet boundary conditions such as turbulent intensity have important effects on flow fields. Nonetheless, the influence of inlet turbulent intensity on hemolysis is not yet clear. This study investigates the influence of turbulent intensity on the prediction of flow field and hemolysis in the FDA benchmark nozzle model. Three configurations are investigated: first is the original nozzle model (with a gradual contraction, throat, and sudden expansion); the second is composed only of the throat and sudden expansion; the third one is similar with the second, but with a shorter throat. Four turbulent intensities are considered, ranging from 1% to 20%. For the first configuration, the influence of turbulent intensity on both flow field and hemolysis is very small and limited prior to the gradual contraction, while for the other two configurations, the influence is considerable. The jet breaks down sooner with increased turbulent intensity. Both turbulence dissipation rate and Reynolds stress increase in the throat with increased turbulent intensity, but decrease after the jet breaks down. The influence of turbulent intensity is more considerable for the configuration with a shorter inlet. The influence of turbulent intensity on the prediction of hemolysis is up to 38.5%. This study shows that turbulent intensity can have considerable influence on the prediction of flow field and hemolysis in blood-contacting devices, thus should be taken in account when conducting blood compatibility design.