AC7-03

Front Page

Description

Test Data

CFD Simulations

Evaluation

Best Practice Advice

Abstract

Heart failure is a cardiovascular disease, which affects millions of people worldwide. If the heart failure is to severe, a heart transplantation is the gold standard for treatment. Unfortunately, a significant shortage of donor hearts exists worldwide. A technical solution to overcome this gap between demand and availability are Ventricular Assist Devices (VADs). The VADs are mainly implanted within the body of the patients and assist the weak heart by creating the needed pressure to sufficiently supply the circulatory systems.

The devices must be designed in such a way that the VADs operating range maintain the blood flow in the circulatory system. For this purpose, a defined pressure head $H$ must be built up at a certain blood flow rate $Q$. Whether a VAD design meets these fluid mechanical requirements can be checked by flow simulations in the pre-clinical evaluation. Furthermore, a VAD must be designed for highest hemocompatibility, which means that the blood components in the flow are not damaged due to non-physiological flow condition. This can be checked by analysing the fluid dynamical stresses $\tau$ by flow simulations and combine them with a numerical blood damage prediction model (these are called the hemodynamical parameters in the following).

In this context, the present ERCOFTAC KB Wiki entry examine the turbulent flow field in a VAD, which is computed by flow simulations. A highly turbulence-resolving large-eddy simulation (LES) is compared as a reference with a unsteady Reynolds-averaged Navier-Stokes simulation (URANS) using a $k$-$\omega$-SST turbulence model (standard simulation setup by industry for VAD simulations) with respect to the computed fluid mechanical and hemodynamical parameters. In particular, the question shall be answered to what extent URANS can reproduce the fluid mechanical parameters (head, efficiency) and hemodynamical parameters (shear stresses and blood damage prediction results) compared to the reference LES. Furthermore, two verficiation methods will be presented by which an adequate shear stress computation for URANS and LES can be checked. In this context, the grid dependency of the analyzed flow quantities will be discussed in detail.

The presented results are part of various publications by the author. More information on the topic can be found in References [1] to [6].

---

Contributed by: Benjamin Torner — University of Rostock, Germany

Front Page

Description

Test Data

CFD Simulations

Evaluation

Best Practice Advice

© copyright ERCOFTAC 2021