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.

Large eddy simulation as a fast and accurate engineering approach for the simulation of rotary blood pumps

“…may influence the credibility of "Light LES" results. In a recent study, Wu et al investigated the influence of inlet turbulence intensities (TI) for the FDA idealized medical device, 23 found inlet TI have a considerable impact on the downstream flow field, the breakpoint of downstream jet moved upwards as TI increased. In this study, no perturbations of the inlet velocity were assumed.…”

“…Therefore, as a comprise, smaller turbulent scales are modeled, leading to turbulence modeling techniques of LES [20][21][22] and Reynolds-averaged Navier-Stokes (RANS). 23 In LES, the large energy-containing motions are resolved while the smaller eddies are modeled, thus provides a better representation of the turbulent flow field compared with the RANS method, for which the whole turbulent field is modeled. Thus, LES has been introduced to predict the flows in medical devices recently, including blood pumps.…”

Numerical simulations of biological flows and their engineering applications

“…15 investigate cell capture in a U-shaped sieve-based microfluidic device by using an immersed boundary–lattice Boltzmann method; Wu et al. 16 present the effect of turbulent inlet conditions on the prediction of flow field and hemolysis in the FDA (US Food and Drug Administration) ideal medical device; Ji et al. 17 investigate the cell localization by considering the dynamic-coupling of dielectrophoresis, alternating current electroosmosis and electrothermal flow; Wang et al.…”

“…Regarding numerical tools used, there are seven papers using immersed boundary methods, 5,7,11,13–15,18 nine papers using body-fitted mesh methods 6,8–10,12,16,17,19,21 and two papers using other methods. 20,22 Among the applications involving moving boundaries, there are seven papers using immersed boundary methods, 5,7,11,13–15,18 one paper using an open source finite element software Elmer, 6 and three papers using commercial software Ansys/Fluent, 8–10,12 indicating that the immersed boundary method is an emerging alternative in solving flows involving moving boundaries and fluid-structure interaction (see also a recent review paper 23 ).…”