Numerical Simulation of Unsteady Flow Past a Rotating Wells Turbine with Modified Blades

Wells turbines used in wave power generation have the advantage of being usable in reciprocating flow, but they also face many unsolved problems, such as self-starting performance, low efficiency, and noise. The purpose of this study is to assess the effect of serrations added to symmetrical blades used in Wells turbines on stall characteristics and lift–drag ratio. In this study, large eddy simulation was employed as numerical method to clarify the spatio-temporal behavior of the flow field, including flow rate fluctuations. In addition to turbine blade modifications, this study also evaluated the effect of changes in rotor solidity on turbine performance. The results show that the serrated turbine had up to a 30% increase in torque over the normal-blade turbine. Additionally, power fluctuations caused by blade stalling were also suppressed. For a tandem arrangement of blades, the effect of wake flow from the front blades on the rear blades was evaluated. Simulations of a serrated blade cascade and turbine rotors have shown that serration processing can improve the performance of Wells turbines. It was also found that not only the interaction between serrated blades but also the serrations themselves have a significant effect on airfoil performance.