A parametric evaluation of the interplay between geometry and scale on cross-flow turbine performance

Cross-flow turbines harness kinetic energy in wind or moving water. Due to their unsteady fluid dynamics, it can be difficult to predict the interplay between aspects of rotor geometry and turbine performance. This study considers the effects of three geometric parameters: the number of blades, the preset pitch angle, and the chord-to-radius ratio. The relevant fluid dynamics of cross-flow turbines are reviewed, as are prior experimental studies that have investigated these parameters in a more limited manner. Here, 223 unique experiments are conducted across an order of magnitude of diameter-based Reynolds numbers ($\approx 8\!\times\!10^4 - 8\!\times\!10^5$) in which the performance implications of these three geometric parameters are evaluated. In agreement with prior work, maximum performance is generally observed to increase with Reynolds number and decrease with blade count. The broader experimental space identifies new parametric interdependencies; for example, the optimal preset pitch angle is increasingly negative as the chord-to-radius ratio increases. Because these experiments vary both the chord-to-radius ratio and blade count, the performance of different rotor geometries with the same solidity (the ratio of total blade chord to rotor circumference) can also be evaluated. Results demonstrate that while solidity can be a poor predictor of maximum performance, across all scales and tested geometries it is an excellent predictor of the tip-speed ratio corresponding to maximum performance. Overall, these results present a uniquely holistic view of relevant geometric considerations for cross-flow turbine rotor design and provide a rich dataset for validation of numerical simulations and reduced-order models.Comment: SUBMITTED to Renewable and Sustainable Energy Review

Experimental data from "A parametric evaluation of the interplay between geometry and scale on cross-flow turbine performance"

The provided MATLAB file contains data from 223 cross-flow turbine experiments conducted at the University of Washington and University of New Hampshire, which are described in detail in "A parametric evaluation of the interplay between geometry and scale on cross-flow turbine performance" by Hunt et al. The "data" struct in the provided file includes time-average and phase-median performance, rotor geometry specifications, and flow properties for each experiment. The "comments" struct describes each field of the "data" struct in detail. Please contact Aidan Hunt at [email protected] or Brian Polagye at [email protected] if you have questions about the data.This data was collected with support from the U.S. Navy's Naval Facilities Engineering and Systems Command (NAVFAC) under N0002410D6318 / N0002418F8702