Data from: Performance characteristics and bluff-body modeling of high-blockage cross-flow turbine arrays with varying rotor geometry

While confinement is understood to increase the power and thrust
coefficients of cross-flow turbines, how the optimal rotor geometry
changes with the blockage ratio---defined as the ratio between the array
projected area and the channel cross-sectional area---has not been
systematically explored. Here, the interplay between rotor geometry and
the blockage ratio on turbine performance is investigated experimentally
with an array of two identical cross-flow turbines at blockage ratios from
35% to 55%. Three geometric parameters are varied---the number of blades,
the chord-to-radius ratio, and the preset pitch angle---resulting in 180
unique combinations of rotor geometry and blockage ratio. While the
optimal chord-to-radius ratio and preset pitch angle do not depend on the
blockage ratio, the optimal blade count increases with the blockage
ratio---an inversion of the relationship between efficiency and blade
count typically observed at lower blockage. To explore the combined
effects of rotor geometry, rotation rate, and the blockage ratio on array
performance, we utilize two bluff-body models: dynamic solidity (which
relates thrust to the rotor geometry and kinematics) and Maskell-inspired
linear momentum theory (which describes the array-channel interaction as a
function of the blockage ratio and thrust). By combining these models, we
demonstrate that the array time-average thrust coefficient increases with
dynamic solidity in a manner that is self-similar across blockage ratios.
Overall, these results highlight key design principles for cross-flow
turbines in confined flow and provide insights into the similarities
between the dynamics of cross-flow turbines and bluff bodies at high
blockage.