Turbulent Blood Flow in a Ventricular Assist Device

Application Challenge AC7-03 © copyright ERCOFTAC 2021

CFD Simulations

Overview of CFD Simulations

Various large-eddy simulations (LES) and unsteady Reynolds-averaged Navier-Stokes (URANS) computations were carried out using the commercial flow solver /*ANSYS CFX (ANSYS Inc., PA, USA)/*. All simulations were performed at the nominal operation (design) point of the VAD. In total, five LES computations on different grid sizes were conducted for the verification of the LES results. The simulation at the finest grid was used as the reference case for the comparison with URANS. For the URANS cases, an extended grid convergence study was performed using seven URANS grids to analyze the influence of the spatial discretization on the main assessment parameters. Additionally, URANS computations with different turbulence models were performed on the finest grid for the comparison with the LES results. The used URANS turbulence models were: a $k$ - $\omega$ model, a $k$ - $\omega$ -SST model, and a $\omega$ -based Reynolds stress model.

Computational Domain

The whole VAD was considered in the numerical analysis. A sketch of the computational domain can be seen in Fig. X. Inflow and outflow cannulas were included in the computational domain. The inlet and outlet of the cannulas were placed sufficiently far away (four and seven impeller diameters respectively) from the pump in order to minimze the influences of the boundary conditions on the results.

Block-structured grids with hexahedral-elements were created using ANSYS ICEM CFD. Since URANS and LES have different requirements for grid resolution and quality, two different, final meshes were created: