Abstract: This paper presents a numerical investigation of the effect of blockage on the hydrodynamic performance of a generic tidal cross-flow turbine. Flows through a three-bladed turbine with a turbine solidity of 0.125 were simulated at field-test Reynolds numbers, O(105- 106), for three different domain sizes that resulted in cross-stream blockages of 6.25%, 12.5% and 50%.
It was found that increasing the effective blockage from 6.25% to 50% led to an increase in the maximum power coefficient, CPmax, from 0.07 to 1.13.
Furthermore, the power curve shifted to a larger range of tip speed ratios. This was found to be due to a reduced flow impedance, i.e. increased streamwise flow velocity, caused by flow confinement effects that occur at higher blockage ratios.
