Development, validation and use of a CFD model for iterative design improvement of the Calon MiniVAD

Aim: Develop and validate a computational fluid dynamics (CFD) model of theCalon MiniVAD, and use it to produce an impeller design with a flat pressure–flow (HQ) curve, maximum efficiency (η) and minimal shear stress.Methods: A set of impellers were designed and built with identical bladeshapes, but with differing heights. Flow domains were extracted fromthe CAD drawings and meshed. ANSYS CFX was used to calculate theblood flow. A discretization study was performed, and the effects ofpressure-pressure vs pressure-flow boundary conditions, steady vs transient,time step and residuals sizes have been analysed. Flow fields werethen calculated at points along the HQ curve and the estimated pressureheads were compared with those measured in an experimental flowloop. The validated numerical model was then used to implement a seriesof design improvements on the blade (shape, length, width, outlet/inlet angle and number) and on the rotor geometry, volute, outlet pipe andsecondary flow.Results: As the height of the blades on the initial impellers increased from1.5 to 4.5 mm the speed to reach the design point (100 mmHg and 5 l/min)decreased from 5,900 to 5,000 rpm. Characteristics at 10 l/min were:H<35 mmHg and η<12%. After the changes the design speed was reduced(4150 rpm) and the HQ curve was significantly flatter: at 10 l/min, H = 70 mmHgand η = 32%. Additionally pressure loss and shear stress have beendecreased.Conclusions: A validated numerical model of the Calon MiniVAD has been developed and used to improve the characteristics of the pump.