Effect of leading edge and trailing edge serrations on a rotating Wells turbine

Wells turbine used for wave and wind power generation is known to generate loud noise during its operation. Aerodynamic noise reduction is an important issue in the design of the turbines. Since aerodynamic noise depends highly on behavior of the vortices around the turbine and the flow structure in the wake region, understanding of behavior of the unsteady flow past a rotating turbine plays important role. In this study, we modeled Wells turbine with normal (solid) blades and serrated turbine. To visualize the flow separation and vortex generation near the rotating turbine at its startup, LES simulations were performed by using moving mesh and transient inlet condition. In addition to the detailed flow structure around the turbine, the results show that the axial torque of the turbine increases with respect to the monotonically increasing inlet velocity. It is also found that positive axial torque generated for the normal and trailing edge serrated turbines as the inlet flow velocity increased, but no torque was obtained for the leading edge serrated turbine due to flow separation at the leading edge.