Theoretical vertical-axis tidal-current-turbine wake model using axial momentum theory with CFD corrections

Abstract

The wake from a tidal current turbine has a significant impact on a tidal farm. A single turbine wake would affect the turbine located adjacent or downstream. Two equations are proposed to predict the mean velocity within the wake of a vertical-axis turbine. The first equation used to predict the efflux velocity is derived based on the axial momentum theory and dimensional analysis. Efflux velocity is the minimum velocity closest to the turbine downstream. The second equation used to predict the lateral velocity distribution is derived based on Gaussian probability distribution. The predictions are compared with the existing experimental and numerical results. Validation of the equations gives a variation in the range of 0-1.13% for the efflux velocity by comparing the proposed theoretical works and Dai and Lam's experimental measurements. These equations are the foundation of the analytical method for wake prediction of a vertical-axis turbine.

Temporal Evolution of Seabed Scour Induced by Darrieus-Type Tidal Current Turbine

“…However, the outside tail of the sand dune is a little longer than the inside tail. This is due to the wake asymmetry of Darrieus-type tidal current turbine which has been proposed in paper [17]. In summary, the turbine model used in our experiments is small scale model compared with real tidal current turbine under the constraints of the experimental setup.…”

“…However, the outside tail of the sand dune is a little longer than the inside tail. This is due to the wake asymmetry of Darrieus-type tidal current turbine which has been proposed in paper [17].…”

“…Flow acceleration can be clearly observed close to the rotating blade tips. Ma et al [17] proposed a wake model for vertical-axis tidal current turbine. In their model, the minimum velocity position in lateral wake distribution deviated from centerline at efflux plane.…”

Tip-Bed Velocity and Scour Depth of Horizontal-Axis Tidal Turbine with Consideration of Tip Clearance

“…Generally, the empirical equation could estimate the seabed scour of a tidal turbine within a 30% error range. Based on Hill et al [22], and Chen [38] results, the statistical functions using correlation coefficient (R), mean absolute error (MAE), root mean squared error (RSME), and scatter index (SI) in Equations (22)- (25) [40][41][42] were calculated to evaluate the performance and accuracy of Equation (19).…”

“…The rotating propeller releases energy into the water through the production of forward thrust, and a turbine extracts energy from the water through rotations. Lam et al and Ma et al [18,19] found that strong shadowing effects appeared on the turbine through the analysis of experimental and numerical results. Chen and Lam [5] studied the shadowing effect of a turbine rotor and showed that the velocity of a slipstream is accelerated by about 105%.…”