Experimental And Numerical Investigation Of Oscillating Water Column Wave Energy Convertor

Oscillating Water Column (OWC) wave energy convertor for electricity generation is most widely used in the world. The investigation of the OWC wave energy convertor can provide guidance to the research and design of the highly efficient wave energy converting and utilizing system, which is also extremely important to solving the nowadays energy and environmental crisis. In order to develop the OWC wave energy converting system practically, the physical model experiments and numerical simulations are employed to investigate the wave energy converting device systemically.In the experimental study on the air chamber, it is found that the oscillating amplitudes of the free surface and relative pressure in the chamber and the air flow velocities in the duct are related to the incident wave parameters. The effects of the chamber width, the draft of the chamber skirt, the thickness of the chamber skirt, bottom slope and the opening styles on the chamber performance are studied. The key parameters are selected for the numerical simulations, which will be different according to the variation of the chamber profiles.The 2D and 3D numerical wave tanks are established based on the two-phase air-water VOF model. The free surface methods applied in the thesis are validated with the experimental results. The numerical results of the wave parameters such as wave periods, wave lengths and wave heights show good agreement with the analytical solutions.In the 2D numerical simulation of the air chamber, the distributions of the relative amplitudes against the incident wave period are divided into the short-period zone, peak-value zone and long-period zone. The still water depth in front of the chamber, the draft of the chamber skirt and the thickness of the chamber skirt have effects on the chamber performance when the chamber width is small. The peak-value zone will disappear when the chamber width is large, and the effects of the above parameters are minor.The 3D numerical wave tank can predict the relative amplitudes and the relative pressure in the chamber and the air velocities in the duct more precisely than the 2D numerical wave tank. In the 3D numerical study, the effects of the chamber width, the chamber length and the duct diameter on the chamber performance are evident. The duct length and its installed position have little influence on the chamber wave energy converting ability. The wave focusing devices can improve the chamber performance in the long period zone. The porous media model can be applied to simulate the pressure loss in the chamber-duct system induced by the impulse turbine, which also has effects on the air flow rate in the duct.The 3D numerical predicting method on the impulse turbine based on the multiple reference frame model is established in the paper. The turbulence model, mesh type and mesh numbers are selected. The comparison with experimental results shows that the 3D numerical results are better than that of the 2D calculation. The air flow field and pressure distribution in the turbine are obtained. The optimal design value of the rotor blade number, the gap ratio of the turbine, the blade inlet angle, the blade setting angle, and the hub-to-tip ratio and the tip clearance are predicted in the calculation. The optimizing design of the ring-type plate covering the blade top and the staggered angle of the rotor blade are also provided.