Computational Fluid Dynamics Analysis of Blade Tip Clearances on Hemodynamic Performance and Blood Damage in a Centrifugal Ventricular Assist Device

Abstract

An important challenge facing the design of turbodynamic ventricular assist devices (VADs) intended for long-term support is the optimization of the flow path geometry to maximize hydraulic performance while minimizing shear-stress-induced hemolysis and thrombosis. For unshrouded centrifugal, mixed-flow and axial-flow blood pumps, the complex flow patterns within the blade tip clearance between the lengthwise upper surface of the rotating impeller blades and the stationary pump housing have a dramatic effect on both the hydrodynamic performance and the blood damage production. Detailed computational fluid dynamics (CFD) analyses were performed in this study to investigate such flow behavior in blade tip clearance region for a centrifugal blood pump representing a scaled-up version of a prototype pediatric VAD. Nominal flow conditions were analyzed at a flow rate of 2.5 L/min and rotor speed of 3000 rpm with three blade tip clearances of 50, 100, and 200 μm. CFD simulations predicted a decrease in the averaged tip leakage flow rate and an increase in pump head and axial thrust with decreasing blade tip clearances from 200 to 50 μm. The predicted hemolysis, however, exhibited a unimodal relationship, having a minimum at 100 μm compared to 50 μm and 200 μm. Experimental data corroborate these predictions. Detailed flow patterns observed in this study revealed interesting fluid dynamic features associated with the blade tip clearances, such as the generation and dissipation of tip leakage vortex and its interaction with the primary flow in the blade-blade passages. Quantitative calculations suggested the existence of an optimal blade tip clearance by which hydraulic efficiency can be maximized and hemolysis minimized.

Numerical Simulation of LVAD Inflow Cannulas with Different Tip

“…The estimation value of blood damage was between 5 × 10 -5 % to 20 × 10 -5 %. The acceptable estimation value of blood damage for LVAD was 10 -3 % [27,28]. So the blood damage in inflow cannula was negligible.…”

Validation of an Open Source Framework for the Simulation of Blood Flow in Rigid and Deformable Vessels

“…where Σ̂s and Σ̂p are appropriate approximations of the structure Schur complement and the pressure Schur complement To approximate Σ s , we use (C + r f R f ) −1 ≈ H, where H is defined in (10). Thus, we have:…”

“…We can rewrite (6)- (7) in the form (8) where (9) At every time level t n+1 , to solve system (8) we use the left preconditioned GMRES method. As preconditioner, we use an upper-triangular variant of the pressure corrected Yosida splitting [23,39] given by (10) The above preconditioner is a suitable approximation of the U factor in the exact block LU factorization of matrix A in (9): (11) See also [40,41,42,43] for more details.…”

“…It has been extensively applied over the years to study the physiology and physiopathology of the cardiovascular system [1,2,3] and to patient-specific planning of interventions for cardiovascular disease [4,5,6]. It has been used in the medical device industry to develop and/or analyze the performance of prosthetic heart valves [7], stents [8,9], ventricular assist devices [10], blood filters [11] etc. In addition, CFD results are also being used by some manufacturers to help demonstrate safety and efficacy of a device as part of the pre-market device submissions to the U.S. Food and Drug Administration (FDA) [12].…”

Towards computational prediction of flow-induced damage of blood cells using a time-accumulated model

“…In this paper, we compare three power-law models: i) average shear stress model (Goubergrits and Affeld, 2004), ii) Temporal Differential Model (Goubergrits and Affeld, 2004), and iii) Total Differential model (Yeleswarapu et al, 1995). The power-law model established by Giersiepen et al (1990) has been considered in various studies as a fundamental model to estimate blood damage (Einav and Bluestein, 2004;Nobili et al, 2008;Wu et al, 2010;Wu et al, 2011). The limitation of this model is the requirement of empirically deriving the coefficients of the power law formulation for each prosthetic device (Ozturk et al, 2016), and their physical inconsistencies.…”