Wake Velocity Distribution Of Vertical-axis Tidal-current Turbine

The research of turbine wake is important for the research of the characteristics of the flow field around the tidal current turbine,the analysis of load and hydrodynamic performance of turbine.It is also important for the arrangement of tidal current turbine array.The thesis uses both theoretical method and CFD simulation to simulate the flow field of vertical axis tidal turbine wake using k-? model and to compare the results of CFD simulation and theoretical deduction with the results of former researchers.Equations to predict velocity distribution of vertical axis turbine wake have been proposed.The equations to predict velocity distribution of vertical axis turbine wake consist of efflux velocity equation and the lateral velocity distribution equation.The equation used to predict the efflux velocity is derived based on the axial momentum theory and dimensional analysis.The equation used to predict the lateral velocity distribution is derived based on Gaussian probability distribution.These two equations can predict the velocity distribution of the whole flow field of the vertical axis turbine wake.On the basis of the equations,different thrust coefficients are obtained for different tip ratios and solidities.In this way,efflux velocities for different conditions can be obtained.These equations are the foundation of the analytical method for wake prediction of a vertical-axis turbine and the research of the vertical-axis turbine array.Besides the research on single vertical-axis turbine wake,double vertical-axis turbine wake has been studied in this thesis.CFD models of double vertical-axis turbine wake and mirrored single vertical-axis turbine wake have been built and the simulations have been conducted.Compared the velocities in the wake of mirrored single and double vertical-axis turbine,the efflux velocity and lateral velocity distribution equations of mirrored single and double vertical-axis turbine wake have been proposed.The results of this research can provide reference for related scientific work.In addition,comparision of turbulence intensities of single and double verticalaxis turbine wake.The distribution of turbulence intensities is compared with velocities distribution.The wake structures of single and double vertical-axis turbine wake have been proposed.