Topology optimization method applied to ventricular assis device impeller and volute design.

Author(s)

Luís Fernando Nogueira de Sá

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Escola Politécnica (EP/BC)
• Defense date: 2019-10-24

Examining board members

Emilio Carlos Nelli Silva; Aron Jose Pazin de Andrade; Oswaldo Horikawa; Renato Pavanello; Juan Sergio Romero Saenz

• Advisor: Emilio Carlos Nelli Silva

Abstract

Ventricular assist devices (VADs) are mainly small-scale pumps that assist the blood to flow. The design of VAD has as the primary requirement low shear stress in order to avoid the death of red blood cells. The topologies of the rotor and volute of the VAD can directly influence the flow condition. This work aims to optimize the design of the rotor and volute of a radial VAD, based on the topological optimization method. The constitutive equations are solved by using the finite element method for the Carreau-Yasuda blood flow model, in a rotational reference in the case of the rotor, and in a fixed reference frame in the case of the volute. The fluid flow is modeled in porous media using the Brinkman equation; also, the turbulence model of Spalart-Allmaras is used. The objective function is the minimization of viscous energy dissipation, aiming to minimize the hemolysis rate indirectly. The implementation of the algorithms is performed using the FEniCS environment coupled with the dolfin-adjoint and pyIpopt libraries. The optimization problem is solved using the PyIpopt algorithm. The optimized topologies are built using 3D printing. The prototypes are tested with water, and the results are used to calibrate a 3D complete VAD computational model. Finally, the model is simulated with blood at 5l/min and 100mmHg and compared with a straight blade impeller. A reduction of 20% in the viscous dissipation is observed. (AU)

• FAPESP's process: 16/19261-7 - Topology Optimization Method Applied to Ventricular Assist Device Rotor and Volute design
• Grantee: Luís Fernando Nogueira de Sá
• Support Opportunities: Scholarships in Brazil - Doctorate