Numerical Simulation And Experimental Study On Hydrodynamic Characteristic Of Vertical Axis Tidal Turbine

As a kind of renewable energy, the tidal current energy (TCE) is becoming a hot researchtopic in all over the world. TCE has promising exploitation potentiality in China because ofrich resource. Vertical axis tidal turbine is one type of the extensive application devices forTCE, which has no influenced with current direction. Some research fruits have beenachieved in recent years. However, the study about understanding and analysis method for thecharacteristics and mechanism of unsteady flow field, the hydrodynamic performance andloads of turbine, the influence of the parameters etc, are still very limited. So, based on thebackground of the hydrodynamic design of vertical axis tidal turbine, the hydrodynamicproblems of two kinds of vertical axis tidal turbines-the fixed pitch and free variable pitch-have been systematically studied and analyzed in this paper. Theoretical analysis, model testsand numerical simulating methods are used to set up the dynamic model and method. Thiswork has theoretical and practical significance to in-depth grasp of the mechanism,phenomena and laws of the hydrodynamic of vertical axis turbine, and to provide theoreticalmethods and design techniques for developing reliable and efficient tidal current energydevices.At first the working principle, classification and performance characteristics of verticalaxis tidal turbine are described in this thesis. And the motion and force characteristic of bladeand turbine are analyzed during running. The hydrodynamic parameters and similarity rate ofturbine have been analyzed by dimensional analysis, and then the affect of major factors havebeen preliminarily discussed for the hydrodynamic characteristics of the turbine.A model test system of vertical axis tidal turbine has been designed and manufactured aswell as a test platform of hydrodynamic characteristics. The test scheme and test methods forthe performance and loads are presented and then model experiments are carried out aboutthose two kinds of turbine. Based on the test results, the hydrodynamic characteristics andaffecting factors of the two type turbines have been analyzed in order to get a morecomprehensive understanding and preliminarily optimization of the main parameters. Theanalysis of the test results supplies a lot of useful information for the hydrodynamic design ofvertical axis tidal turbine and all of these results can be used to validate numerical simulationmethod.One aim of this work is to improve the performance of CFD method for the vertical axistidal turbine, so the accuracy and reliability of CFD are carried out by analyzing the effect of turbulence models, mesh size and time step on the calculation results by comparing with theexperimental results. A method based on Euler-Lagrange particle tracking model is proposedto capture the wake of the blade. The developing process of the blade wake and interferencebetween blade-wake can be successfully expressed by this method. The advantage of CFDmethod is that it can provide more physical quantities and flow field details than experiment,such as velocity distribution, pressure distribution and vorticity distribution, which aredifficult to measure in experiment.In the research of turbine hydrodynamic characteristics, a coupled dynamic model and acoupled numerical simulation method are proposed for the unsteady rotating of vertical axistidal turbine in this thesis. Then the coupled method is validated by comparing calculationresults with experimental ones. Finally based on the results of series examples, the detailedanalysis is conducted on the hydrodynamics of fixed pitch vertical axis turbines under theinfluences of different principal parameters such as TSR, density, Reynolds number, bladepreset pitch and blade installation position. The mechanism, manner and law of the influenceby these parameters are summarized by combing with the test results. The simulation of freevariable pitch turbine is achieved, based on the coupled numerical simulation of fixed pitchturbine and the dynamics and kinematics equations of free variable pitch turbine. And then theeffects of principal parameters are studied for the turbine. At the end of this research work, the3D and3D with free surface simulation are carried out for free variable pitch vertical axistidal turbine, the effect of3D and free surface on the hydrodynamic characteristics of turbineare studied. The research about wall interference has been done also.