Effects of dimensionless parameters on the performance of a cross-flow current turbine

Abstract

Cross-flow turbine performance is sensitive to multiple dimensionless parameters, including the Reynolds number, blockage ratio, and Froude number, based on both turbine submergence depth and overall channel depth. Here, we experimentally isolate the effects of each parameter. Turbine performance and free surface deformation were characterized in a recirculating flume at a baseline operating condition. Then, each parameter was independently increased by approximately 30% from the baseline case while all others were held roughly constant. Turbine performance, quantified by the power coefficient, was most sensitive to an increase in Reynolds number, followed by the blockage ratio and submergence depth Froude number. Increasing the channel depth Froude number had a negligible effect on performance. In contrast, increasing the channel depth Froude number caused the largest change in free surface deformation, and increasing the Reynolds number had a negligible effect on free surface deformation relative to the baseline case. Turbine performance changes are caused by a combination of blade hydrodynamics and strut losses, both of which are affected differently by each dimensionless parameter. These results suggest that each dimensionless parameter describes different fluid dynamics and that all four parameters should be considered during experimental design. Notably, we observe that turbine performance is sensitive to the submergence depth Froude number, a parameter that has not been previously explored in the archival literature.