Investigation of phase difference and separation distance effects in the design of a dual flapping hydrofoil turbine

Abstract

In this study, a parametric analysis was conducted for the design of a suggested dual flapping hydrofoil turbine. A Navier–Stokes‐based computational fluid dynamics code was utilized for the analysis while varying the pitch angle, reduced frequency, separation distance, and phase difference. The smallest pitch angle of 60° and the reduced frequency of 0.1 among the given ranges of the parameters were fixed for the first parametric analysis. After an assessment, the 90° front‐lead with the longest distance of 6c and the 90° rear‐lead with the shortest distance of 2c were chosen for further parametric analysis based on a suggested performance indicator and a margin for improvement. It was derived from a subsequent parametric analysis that a 70° pitch angle, 0.12 reduced frequency, and a 4c distance for the 90° front‐lead was the final optimum with 59.48% efficiency and 55.44% fluctuation according to the performance indicator as well as the system length and power balance of dual hydrofoils.