TEAMER: Cross-flow Turbine Hydrodynamics

The objective of this work is to validate RANS and LES computations of cross-flow turbine hydrodynamics using laboratory scale measurements. Validation involves the comparison of time-and phase averaged performance metrics and flowfields across the widest practical range of turbine kinematics and geometry. Turbine performance was monitored use a series of six-axis load cells and flowfields were measured using a particle image velocimetry (PIV), both within the rotor and in the wake. Six test cases were chosen. Three involve operating a turbine with symmetric foils at a constant rotation rate and under intracycle speed control (both optimally and sub-optimally). Intracycle control of cross-flow turbines has been shown to have significant potential to increase turbine power output. Such control significantly modulates separation and recovery dynamics and therefore poses a challenging set of cases for simulation validation. The second group of three cases kept the rotation rate constant while varying the geometric camber of the foils by up to 2% in either direction. By changing camber, the pressure gradients and flow curvature on the surface of the blade can be varied, providing a significant test of the efficacy of near-blade modelling.

A total of six primary validation cases are explored in two broad categories. For each of these cases experimental and computational performance and flowfields are compared. A significantly greater number of experimental and computational cases were obtained to broaden the parameter space and to inform the sensitivity of either the experimental or computational parameter space, some of which are summarized below. Exploration of intracycle control kinematics for a two-bladed turbine: (1) Optimal tip-speed ratio for constant speed control. (2) Intracycle kinematics corresponding to optimum power enhancement at the same mean tip-speed ratio (3) Intracycle kinematics corresponding to poor performance at the same mean tip-speed ratio Exploration of cambered blade geometry for a one-bladed turbine operating under constant speed control: (4) Symmetric NACA 0018 foil at TSR = 2 (5) Cambered NACA +2418 foil at TSR = 2 (6) Cambered NACA -2418 foil at TSR = 2

A portion of the intracycle control data were published by Athair et al (2023) and presented at EWTEC 2023. See "Intracycle Control Sensitivity of Cross-Flow Turbines" resource below.

A portion of the cambered foil data is being prepared for peer reviewed publication which will be added to this submission when available. A. Athair, C. Consing, J. Frank, O. Williams. The impacts of geometric camber on cross-flow turbine performance and hydrodynamics.

Both experimental and corresponding simulation data are available in this dataset. The simulation data were generated by the team of Jennifer Franck at the University of Wisconsin-Madison.