Equations used to predict the velocity distribution within a wake from a horizontal-axis tidal-current turbine

The investigation of the wake from a tidal-current turbine becomes important when considering a tidal farm. Each single turbine wake in a turbine farm would significantly affect the performance of another turbine located adjacent or downstream. In this study, two novel analytical equations are developed to predict the mean velocity within the wake of a tidal-current turbine. The equations are proposed to predict the initial velocity close to the turbine and the lateral distributions at various sections downstream, respectively. The first equation for the initial flow prediction is derived based on the axial momentum theory and dimensional analysis, while the second equation for lateral velocity distribution prediction is derived based on Gaussian probability distribution. The derivation of the proposed equations is presented and their predictions are compared with the existing experimental and numerical results. Validation of these novel equations gives a variation of 6% at the initial flow and 8% at the lateral sections compared to the experimental and numerical results. These equations are potentially the foundation of the analytical method for wake prediction of a tidal turbine.