Heterogeneous comparative effects of casing grooves on a submersible axial turbine performance for wave energy conversion

Wells turbines that extract power for oscillating water columns suffer from low performance and limited operating range. In the present work, the submersible axial turbine is used to overcome these drawbacks. The performance of the submersible turbine is accomplished firstly to introduce a proof of concept and then execute the new modifications such as the casing groove treatments. In sequence, six shapes of tip grooves are performed in the current work to improve the overall turbine performance. The turbine performance is herein demonstrated by solving numerically 3D incompressible Reynolds Averaged Navier–Stokes equation. The performance is demonstrated according to the flow coefficient, pressure coefficient, torque coefficient, and turbine efficiency, as well as the flow and pressure distributions around the turbine blades. The results showed that the immersed Wells turbine has higher performance with a wider operating range compared with the conventional Wells turbine. Furthermore, a comparison was done between six and eight blade rotors, where the latter is more convenient for different operating conditions. Additionally, more performance enhancements and a wider range are achieved using three of the proposed groove shapes, where the triangle shape was the best choice.