Description AC7-03
Turbulent Blood Flow in a Ventricular Assist Device
Application Challenge AC7-03 © copyright ERCOFTAC 2021
Description
Introduction
Ventricular Assist Devices (VADs) are implanted in patients with severe heart failure. Today, nearly all VADs are designed as turbomachinery, since they have a higher power density as pulsatile pumps, and therefore can be implanted within the human body.
By using Computational Fluid Dynamics (CFD), VADs must be designed and optimised in such a way that they reproduce a physiological pressure increase in order to sufficiently supply the body with enough blood flow. Furthermore, they must be designed in order to guarantee that the blood, which passes the VAD, is not damaged due to non-physiological flow conditions (high shear stresses, stagnation areas, high turbulent kinetic energy (TKE) regions, ...) in the device.
The CFD simulation in a VAD can be challenging, since the inflow is laminar and all turbulence is produced within the pump and decays shortly after the pump outlet. Furthermore, the pump Reynolds number is small with compared to industrial pumps (), and transition might occur.
In this respect, the aim of this study is to investigate the suitability of different URANS methods (with different turbulence models and solver settings) for the flow computation in an axial VAD. Furthermore, the influence of the grid resolution will also be investigated based on a extended grid study. The flow fields of the URANS simulations will be compared with a highly turbulence-resolving large-eddy simulation. Here, both fluid mechanical parameters, such as the pump characteristics and velocity fields, as well as haemodynamic parameters, such as the haemolysis index MIH or stagnation zones, are investigated.
Relevance to Industrial Sector
The flow computation in a Ventricular Assist Device (VAD) is an important procedure for the VAD design and optimization in the pre-clinical evaluation. The aim of these CFD studies is, on the one side, to guarantee that the VAD offers an physiological relevant pressure increase at the chosen desing point to sufficiently support the VAD patient. On the other side, haemodynamical parameter must be evaluated in these design studies. Here, it is important that the CFD reflects relevant regions for potential blood damage or thrombi formation, so that these regions can be minimised in the design procedure. Additionally, CFD studies are important in VAD studies to compare different designs to find the pump with the highest haemocompatibility (lowest blood damage).
When the VAD designer is able to find a good VAD design by CFD, some amount of in-vitro (test-rig for pump performance or hemolysis [red blood cell damage]) or in-vivo (animal trials) testing can be reduced.
Design or Assessment Parameters
Flow Domain Geometry
Flow Physics and Fluid Dynamics Data
Contributed by: B. Torner — University of Rostock, Germany
© copyright ERCOFTAC 2021