Numerical analysis of damping induced by impulse turbines for wave energy conversion

The oscillating water column (OWC) based wave energy devices require a turbine for the conversion of wave energy to electrical energy. Customarily, Wells and impulse turbines have been widely accepted for this energy conversion. However, the damping (i.e. the pressure drop developed based on volume flow rate) induced by the turbine significantly influences the performance of the OWC. The present study involves two different impulse turbines that is, reference and optimized. Initially, the reference turbine was numerically validated with two different turbulence models (k-ε and SST). It was found that the SST predicted better than k-ε in terms of flow separation and efficiency. This numerical methodology was extended to the optimized turbine and detailed flow physics has been presented in this article. Furthermore, both the turbines were compared in terms of pressure drop, turbine pressure coefficient, and turbine damping coefficient. It was observed that the induced damping by the optimized turbine is less than the reference turbine. Finally, different diameters were arrived from the optimized turbine by the principle of dynamic similarity to match with an available optimum range of damping.