Research On Hydrodynamics Of Tidal Turbine Bionic Blades

As a core component of the impeller-type tidal turbine,the hydrodynamic performance of the blade will directly affect the power generation efficiency of tidal turbines.It is found that imitation of the leading-edge tubercula of the humpback whales has a good effect on the aerodynamic performance of the airfoil.In this paper,the influence of the leading-edge protuberances on the hydrodynamic performance of the tidal turbine straight blade is studied by the flume experiment and numerical simulation method.It also provides experimental basis for the research of tidal turbines for bionic blades with leading-edge protuberances.First of al,studying the effect of Reynolds Number on the improvement of Hydrodynamic Performance by leading-edge protuberances through flume experiments,Reynolds number is an important research parameter in fluid mechanics research.The object are a standard blade model with a smooth leading-edge and a bionic blade model with a leading-edge protuberances and both of them with an airfoil section of NACA0018.flume experiments are carried out to investigate the hydrodynamics performance of a baseline straight blade and a bionic blade at Reynolds numbers 0.4×10~5,1.2×10~5,1.6×10~5,and 2.2×10~5.The experiments show that in the range of angle of attack less than 33°,the characteristics of lift coefficient,drag coefficient and lift-to-drag ratio of the bionic blade and the standard blade have the same tendency under four different Reynolds numbers.Although the bionic blade loses the maximum lift coefficient of the standard blade,the leading-edge protuberances has the effect of significantly delaying stall and drag reduction.In post-stall regime,The maximum lift coefficient of the bionic blade is increased by 14.09%,the resistance coefficient is reduced by 30.28%,and the maximum lift-drag ratio is increased by 63.64%than standard blade.So,The bionic blade with leading-edge protuberances has better hydrodynamic performance than standard blade.Secondly,When Re=0.4×10~5,study on the influence of the leading-edge protuberances on the flow field around the blade through the flow field display experiment,Tracking the change of flow field in the section of standard blade and cross section of crests and troughs of bionic blades by dyeing method,It show that:Bionic blades are more prone to flow separation at wave troughs,and the flow is not easily separated at the wave crests,and the reverse vortices and free vortices are easily formed on both sides of the wave crests,thereby suppressing the flow separation and achieving the effect of delayed stal ing.Finally,the principle of action of the leading-edge protuberances on the flow field is studied through numerical simulation.When Re=3.6×105,Numerical simulation analysis of bionic blade model and standard blade model by ANSYS CFX software,The results show that the bionic blade's lift coefficient,drag coefficient,and lift-drag ratio increased by 4.755%,decreased by 47%,and increased by 11.94%,The analysis of the blade surface pressure and streamlines results in the same conclusion as the flow field display.The results of the study found that the leading-edge protuberances and vortex generators have similar working principles.The results of the flume experiments and numerical simulations made in this paper can be used as the basis for the study of tidal turbines.