| The IVAS (Innovative Ventricular Assist System) pump, which is being developed at The Cleveland Clinic Foundation, is a non-pulsatile centrifugal blood pump. The primary objective of computational fluid dynamics (CFD) in this work is to aid in the design from the fluid mechanics point of view, i.e., to investigate the flow behavior inside the pump. A three-dimensional (3D) unsteady incompressible Navier-Stokes solver has been developed based on a new algorithm. The new flow solver has the following features: (1) accurate mass and momentum conservation; (2) little or no spurious spatial oscillation; (3) a small amount of numerical viscosity; (4) no numerical instability; (5) no difficulties in the pressure equation convergence; (6) robustness for high Reynolds number for the no turbulence model. There are three parts of the pump that need to be analyzed: (a) primary pump; (b) secondary pump; (c) journal bearing. In the investigation of the primary pump, 2-1/2-dimensional (2.5D) and 3-dimensional single passage models, and mean-line Pumpa code (one-dimensional (1D) model) developed by NASA Lewis Research Center are used. The 1D model, based on empirical data is simple and fast. The 2.5D single passage model has been tested as a feasible tool for a parametric study and the 3D model captures some flow structures which can not be seen through the 2.5D model. For the secondary pump, there is no conventional design tool available because of its unconventional features. The 3D computational analysis investigates the flow patterns for different designs and the tip clearance effect on the pressure head. For the journal bearing design, the 3D simulation captures the flow patterns and a parametric study is performed. For all three parts, the shear stress distributions are calculated as a measure of the biological effects of the flow regimes to the blood. The new solvers including the 2.5D, the 3D, and the axisymmetric code work as useful tools in the designing of the IVAS. Simulation results provide designers with important information to improve the flow behavior inside the pump. Furthermore, these tools are not limited to the blood pump design, but can be used for other turbomachinery design as well. |
