DOI: 10.5061/dryad.mpg4f4r8p
title: Data from: An experimental evaluation of the interplay between geometry and scale on cross-flow turbine performance

description: 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 (≈8×104–8×105) 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 clarifies parametric interdependencies; for
 example, the optimal preset pitch angle is increasingly negative as the
 chord-to-radius ratio increases. As 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.
description: This data was collected using custom experimental test rigs at
 the University of Washington and University of New Hampshire, both of
 which are described in the supporting manuscript. The raw data for each
 experiment was processed using custom MATLAB code, and the aggregate
 time-average and phase-median results for all experiments are provided
 here.
description: # Data from: An experimental evaluation of the interplay between geometry
 and scale on cross-flow turbine performance Dataset:
 [https://doi.org/10.5061/dryad.mpg4f4r8p](https://doi.org/10.5061/dryad.mpg4f4r8p) Supporting Article (*Renewable and Sustainable Energy Reviews*): [https://doi.org/10.1016/j.rser.2024.114848](https://doi.org/10.1016/j.rser.2024.114848) Supporting Article (Open-Access on arXiv): [https://doi.org/10.48550/arXiv.2310.20616](https://doi.org/10.48550/arXiv.2310.20616) ## Description of the data and file structure This dataset represents 223 cross-flow turbine experiments exploring the effects of the Reynolds number, blade count, chord-to-radius ratio, and preset pitch angle on turbine performance. The experimental methods and results are described in detail in our paper: ["An experimental investigation of the interplay between geometry and scale on cross-flow turbine performance"](). The experiments were conducted at the University of Washington and the University of New Hampshire. The experimental data for all experiments is provided as a single file, `HuntEtAl_GeometryScaling_DataSet.mat`, which contains two variables, `data` and `comments`. #### `data` The `data` variable contains a structure of aggregate performance data, flow field data, and rotor geometry details for all turbine experiments. Each row of the structure provides performance, flow field, and geometry data from an individual turbine experiment. Each experiment corresponds to a unique combination of the Reynolds number, blade count, chord-to-radius ratio, and preset pitch angle tested across a range of tip-speed ratios. The fields of `data` are categorized and described below: ***Experiment specification*** * `label`: Identifier of the Re, N, c/R, alpha_p configuration of each turbine tested. * `ReD_nom`: Nominal diameter-based Reynolds number. Correpsonds to Reynolds number shown on heatmaps in the publication. * `note`: Additional information about the data corresponding to this experiment. ***Geometric specification*** * `N`: Number of blades. * `cToR`: Chord-to-radius ratio. * `alpha_p`: Preset pitch angle [degrees]. Negative angle corresponds to "toe-out" pitch. * `solidity`: Solidity of turbine, calculated as Nc/(2*pi*R). * `R`: Radial distance to quarter-chord point on blade [m]. * `RPrime`: Radius of the outermost circle swept by the turbine blades [m]. ***Time-Average Performance*** * `TSR`: Measured tip-speed ratio. * `cp`: Turbine-level efficiency as a function of TSR. * `cp_b`: Blade-level efficiency as a function of TSR. * `ct`: Turbine-level thrust coefficient as a function of TSR. * `cl`: Turbine-level lateral force coefficient as a function of TSR. ***Phase-Median Performance*** * `theta`: Azimuthal positions [degrees] that correspond to the provided phase-median data (e.g., cp_phase). * `cp_phase`: Phase-median turbine-level efficiency as a function of TSR and theta. Rows correpsond to the entries of TSR, whereas columns correspond to the entries of theta. * \`cp_b_phase: Phase-median blade-level efficiency as a function of TSR and theta.Rows correpsond to the entries of TSR, whereas columns correspond to the entries of theta. * `cp_std`: Standard deviation of the phase-median turbine-level efficiency curves at each TSR. Equivalent to standard deviation of phase-median blade-level efficiency curves. * `ct_phase`: Phase-median turbine-level thrust coefficient as a function of TSR and theta.Rows correpsond to the entries of TSR, whereas columns correspond to the entries of theta. * `ct_std`: Standard deviation of the phase-median turbine-level thrust coefficient curves at each TSR. * `cl_phase`: Phase-median turbine-level lateral force coefficient as a function of TSR and theta.Rows correpsond to the entries of TSR, whereas columns correspond to the entries of theta. * `cl_std`: Standard deviation of the phase-median turbine-level lateral force coefficient curves at each TSR. ***Flow Parameters*** * `Uinf`: Freestream velocity [m/s] as a function of TSR. * `h`: Dynamic depth [m] as a function of TSR. * `TI`: Turbulence intensity [%] as a function of TSR. * `ReD`: Diameter-based Reynolds number as a function of TSR as measured during the experiment. * `ReRatio`: Ratio between nominal chord-based Reynolds number and measured ReD as a function of TSR. * `Frh`: Depth-based Froude number as a function of TSR as measured during the experiment. * `Frs`: Submergence-based Froude number as a function of TSR as measured during the experiment. * `B`: Channel blockage ratio [%] as a function of TSR as measured during the experiment. Further detail regarding each of these fields can be found in the supporting paper. ### `comments`  The `comments` variable contains a structure that describes the meaning and format of each field in the `data` structure as provided above. Each field of `comments` contains a description for the corresponding field in `data`. ## Code/software It is recommended that MATLAB/Octave be used to view this dataset. ## Access information Other publicly accessible locations of the data: * UW ResearchWorks: [http://hdl.handle.net/1773/50607](http://hdl.handle.net/1773/50607)