Bionic Study Of Horizontal Axis Tidal Turbine Blade Based On Shark Fin

Blades are the core components of horizontal axis tidal turbines. Their efficiencyhas an important impact on the utilization of tidal current energy. At present, manyresearchers actively explore the performance optimization of tidal current turbineblades. After many years natural evolution shark has become the outstandingrepresentative of high speed in marine fish. Their biological structure and movementpattern are extremely suitable for underwater survival, enable sharks possessextraordinary underwater movement performance. Biology research shows that theswimming ability of shark mainly profits from the performance of its caudal andventral fins. Thus this paper will apply the excellent hydrodynamic performance ofshark fins to the blades of horizontal axis tidal turbine, so as to improve theperformance of the turbine from the point of view of bionics.Carcharhinus menisorrah, one of species of sharks, was used as experimentsubjects for this research.Reverse engineering technology was adopted in theextraction process of three-dimensional coordinates of shark fins, then cloud data andbiological feature of which was obtained by the3D optical scanner. Reverse softwaremodule was employed for processing the original data and establishing curved surface.The3D digital model of the shark fin was built subsequently. Thus the bionic blademodel of horizontal axis tidal was finally established.On the basis of which, softwareof CFD and WORKBENCH were employed to analyze the hydrodynamicperformance of bionic blade. Power coefficient and fluid field characteristic of thebionic blade were studied to obtain the value of torque and power under differentworking conditions, the optimal pitch angle that allow highest capacity coefficienttaken place was calculated. Thus the only variable–position relation between theblade chord and rotating plane—was determined. Three-dimensional model of bionicturbine blade based on pectoral and caudal fin were successfully established.Simulated and analyzed the hydrodynamic performance of two kinds of bionicturbine with the method of CFD, obtained performance parameters and flow fielddistribution of bionic turbine. The results with were compared with that of traditionalturbine designed according to the theory of blade element momentum theory. Thedifferences and advantages of bionic turbine were analyzed accordingly.Numericalsimulation deeply revealed the pressure and velocity distribution of bionic blade at rated external flow conditions. Conclusion was drew as follows: bionic turbine basedon shark fin has higher power efficiency coefficient than standard turbine under lowtip-speed ratio range. Bionic blade based on pectoral fin has higher capacitation thanthat based on caudal fin in the larger range of of tip-speed ratio condition;From thestandpoint torque coefficient, the bionic turbine torque coefficient lower than standardturbines in the same conditions, illustrating bionic turbine will need higher flow speedfor startup bionic turbine in practical operation.In low range of tip-speed ratio, bionicturbine can improve the energy efficiency of turbine in certain conditions, generatemore electrical capacity, but the axial force of bionic turbine will increase accordingly,pressure distributions are also unsteady. Thus, each factor should be considered in thepractical application according to the demand of comprehensive balance.Based on the above results, Physical model of bionic turbine was producedaccording to the calculation of optimal pitch angle. Experimental scheme，testequipments and control system were prepared for the conduction of performanceexperiments of bionic turbine. The experimental results are in agreement withoutcome of numerical simulation, the trend of both are in consistence, proving that thenumerical simulation results are relatively correct. The methodologies and outcome ofexperiment provides valuable reference for follow-up study of bionic application intidal turbine. The paper provides an innovative idea for the research of turbine blade,has certain positive role and guiding significance to the development and applicationof tidal current energy.