A novel mechanism of turbulent kinetic energy harvesting by horizontal-axis wind and hydrokinetic turbines

We present a study on the influence of the turbulence generated by a cylinder on the performance of a free horizontal-axis turbine. The analysis focuses on the power coefficient, flow characteristics, and Turbulence Kinetic Energy (TKE) spectral density distribution. The mean velocity, turbulence intensity, and TKE are evaluated in the upstream and downstream planes of the turbine for configurations with and without the upstream cylinder. The results show that the power coefficient exhibits a peak when the rotor rotation frequency coincides with the frequency of vortex shedding from the cylinder, indicating a mechanism of conversion of TKE carried by large-scale structures into mechanical power. It was also observed that the turbine generates downstream turbulence in the absence of the cylinder but reduces the downstream turbulence when the cylinder is present. Spectral analysis of TKE confirms the influence of the frequency of vortex shedding on the velocity recovery of the turbine wake. The main contribution of this paper is the identification of a new mechanism of conversion of the TKE contained in large coherent turbulent structures into mechanical power. This study provides a further understanding of the complex phenomena involved in the interaction between the turbine and the upstream turbulent flow.