Characterization and numerical evaluation of flow and blood damage in a pulsatile left ventricular assist device
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(2020) 42:522
TECHNICAL PAPER
Characterization and numerical evaluation of flow and blood damage in a pulsatile left ventricular assist device Amir Hossein Vakilzadeh1 · Kourosh Javaherdeh1 Received: 7 January 2020 / Accepted: 3 September 2020 © The Brazilian Society of Mechanical Sciences and Engineering 2020
Abstract Each year, thousands of people lose their lives due to left-sided heart failure. Left ventricular assist device (LVAD) is a mechanical pump utilized to aid the function of the left ventricle of the weakened heart. This study investigates flow dynamics, hemolytic and thrombocytopathic characteristics of LVAD with pulsatile flow. To this end, computational fluid dynamics simulations are utilized to predict the levels of hemolysis, thrombosis susceptibility potential and particle residence time in a quantitative manner, and furthermore, we perform dye ejection analysis to understand the pump’s capability to eject old materials. Thus, a set of time-dependent nonlinear partial differential equations are coupled with each other. Blood flow is acquired by solving continuity and momentum equations and levels of hemolysis are computed by coupling two additional scalar transport equations based on a Eulerian transport approach with the governing equations of fluid flow. Additionally, we assess particle residence time and rate of dye ejection according to a continuum-based model. It is depicted, the value of maximum velocity in the pump is much smaller than the axial ones which causes to reduction in red blood cell damage. Average hemolysis obtained its maximum value at the clearance zone, and hemolysis index at the exit of pump is one order lower compared to continuous ones. It is also observed that for all instances of the cycle the maximum residence time concentrates near the outlet domain representing the no accumulation of particles in interior of the pump and capability of the pump to eject material efficiently. Keywords Hemolysis · Thrombosis susceptibility potential · Residence time · Dye ejection List of symbols u Velocity ν Kinematic viscosity f Frequency of piston movement A Amplitude of piston movement Db Mechanical dose HI Hemolysis index H The ratio of plasma-free hemoglobin to total blood hemoglobin MRT Maximum particle residence time TSP Thrombosis susceptibility potential Q Volumetric flow rate
𝜀ij Strain rate HL A scalar variable equal to H1/β c Empirical constant α, β Empirical constants τ Scalar shear stress µ Dynamic viscosity of fluid ṁ Mass flow rate 𝜍 A scalar quantity V Volume of computational domain t Time A Amplitude of piston movement 𝛾̇ w Scalar wall shear rate
Technical Editor: Edson José Soares PhD.
1 Introduction
* Kourosh Javaherdeh [email protected] Amir Hossein Vakilzadeh [email protected] 1
Faculty of Mechanical Engineering, University of Guilan, Rasht, Iran
Cardiovascular disease is the major cause of fatality globally [1]. About a quarter of America’s deaths in 2010 were due to heart diseases [2]. Heart failure (HF) is
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