Topology Optimization Method Applied to Ventricular Assist Device Rotor and Volute design

Abstract

This work is part of the thematic project "Sistemas Propulsores Eletromagnéticos para Coração Artificial Implantável e Dispositivos de Suporte Circulatório Mecânico", Fapesp number 2013/24434-0. One of the project topic is ventricular assist devices (VAD), which is interpreted here as a small scale radial flow machine (pump) for non-newtonian fluid. The VAD design has a special requisite of low energy consumption and low shear stress aiming to avoid blood cells damage. This objective depends on the rotor and volute topologies. Thus, the rotor and volute can be designed by using the topology optimization method (TOM), which is capable of working with multi-objective requisites and lowers the development time of VADs. Hence, this work aims to optimize the rotor and volute of a VAD by using the topology optimization method. The constitutive equations are solved by using the finite element method considering blood flows (non-newtonian) in a rotary reference frame for the rotor and in a static frame for the volute. The fluid flow is modeled by using a porous media and the Brinkman equations. The modeling of the optimization problem presents a multi-objective function aiming to minimize the pressure loss caused by viscous dissipation, power consumption, vorticity in order to lower the blood stagnation, and the hemolysis ratio. The material model used is based on the density method. This problem will be implemented using the FEniCS environment and the PyIpopt optimizer. The resulting topologies will be built by using a 3d printer an experimental characterization is performed by measuring fluid flow and pressure head. Hemolysis tests will be performed in a partnership with Instituto Dante Pazzanese, which participates in the thematic project. Design for rotors of bi-dimensional radial flow machines of small scale that work in laminar flow, aiming to use them in ventricular assist pumps, and also the experimental comparison between prototypes will be presented as results.