Analysis and validation of hydrokinetic turbine turbulent wake predictions

Turbulent simulations using URANS, DES and LES models are performed for a three-blade marine turbine appended with support struts. Predictions of thrust, power, and the mean and turbulent wakes in the near and intermediate wake region are compared with experimental data. The thrust and power coefficient predictions compare within 5% of the experimental data and results did not show significant dependence on turbulence modeling. The mean wake prediction compares within 7% of the data in the near wake, but shows large 25-35% errors in the intermediate wake. The large errors in the intermediate wake are due to poor predictions of cross plane turbulent fluctuations, which results in the under prediction of the wake diffusion and recovery. LES performs better than other models in the far-wake and behind the struts, when the resolved turbulence is triggered. However, shows the largest error in the intermediate wake as the turbulence in the blade tip region is not predicted accurately. Ongoing simulations are focused on understanding the role of numerical dissipation in the LES. Keywords— Hydro-turbine, Wake, Computational Fluid Dynamics, Turbulence model, Validation

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