Hydrodynamic Anlysis Of Two-dimensional Oscillating Hydrofoil

Tidal energy is clean and renewable energy, its development and utilizationtechnique has the following characteristics: kinetic energy of the flow which is usedto drive the generator is obtained by using tidal current energy conversiondevice.Oscillating hydrofoil is one kind of tidal current energy conversion device,The core part of the device for the hydrofoil, and its hydrodynamic performance has adirect impact on capacity utilization rate, Therefore, the2-D numerical simulation ofthe device is studied in this dissertation.The development of hydrofoil has been reviewed in this dissertation, includingthe finite element method, the flow field calculation based on SIMPLE algorithm, andthe unsteady flow around the turbulence model.Moreover, hydrodynamic performanceof the hydrofoil is also discussed. such as,lift force, drag force and vortex field,which lay the theoretical foundation for the following numerical analysis.In this dissertation，thrust characteristics of oscillating hydrofoil are analyzed bythe FLUENT (CFD code) which is secondly developed based on Reynolds-AveragedNavier-Stokes equations.Meanwhile,the method of dynamic mesh and PostProcessing system are also used. The effects on the oscillating hydrofoil unsteadyhydrodynamic characteristics caused by initial angle of attack, Reynolds number,reduced frequency, amplitude and other parameters are calculated in detail.Conclusions are as follows:Firstly, the periodic motion of oscillating hydrofoil, the generation and sheddingof vortex have influences on lift and drag coefficient and the velocity field. Changesin the pressure of the hydrofoil surface have influences on hydrofoil lift and dragcoefficient. In addition, the hydrofoil lift and drag coefficient and the flow fieldinfluence mutually.Secondly, the best hydrodynamic performance of the hydrofoil and a higherenergy efficiency can be obtained when the initial attack angle is10degree, thevibration frequency is from5°to10°, flow velocity is between1m/s to1.5m/s andthe vibration amplitude is5°to10°.Thirdly, the hydrofoil tip is sensitive to the incoming flow at high velocity, highangle of attack, large vibration amplitude and high frequency. In this case, it is easy tocause energy loss.In this dissertation, the hydrofoil lift force, drag force and flow field areinvestigated under different conditions, The change rules that are found in theresearch lay a foundation, for the future in-depth study of hydrofoil.