Interaction between instream axial flow hydrokinetic turbines and uni-directional flow bedforms

A series of experiments were completed to investigate the interactions between relatively large-scale sediment dunes and axial flow hydrokinetic turbines. Baseline experiments were completed under clear water conditions to assess local scour impacts of single and two-turbine installations. Spatio-temporal measurements of bed elevation were obtained simultaneously with turbine voltage output, from which a measure of the instantaneous rotor angular velocity was used as a proxy for turbine response to unsteady loads. These experiments were completed in a mobile bed of 1.8 mm coarse sand with migrating bedforms. A bedform tracking routine was used to analyze streamwise bed elevation profiles to estimate bedform geometric characteristics and their corresponding impact on turbine performance. Cross-correlation analysis was also performed, investigating critical relationships between approaching bedform crest location, height and the corresponding turbine voltage output. In parallel with the analysis on bedform effects on turbine performance, an extended region downstream of the rotor location was analyzed to investigate how bedform geometric characteristics changed along the channel after turbine deployment.