Experimental Study On Hydraulic Characteristics Around Surface Irregularity-Offset Into Flow And Marine Current Energy Converter

This thesis has included two main parts: (1) Experimental study on testing flow field of irregularity---offset into flow with PIV, (2) Experimental study on marine current energy converter.With the height of discharge structures increasing, the problem of high-velocity flow cavitation has been concerned. Restricted by construction conditions, there are many irregularities in spillway dams, spillway tunnels and chute spillways of high-head discharge structures. When high-velocity flows over them, cavitation phenomena will occur. Cavitation erosion arises from the cavity flow from underpressure to higher pressure. In order to prevent the erosion due to the cavitation in high-velocity flow, an economic and effective measure is to set up aerators for generating forced aeration in underpressure cavitation regions or upper locations liable to cavitation erosion. By far, the research on aeration cavitation-alleviation for spillway dam is relative thorough. But there is lack of researches on the corresponding relations of every parameter in the cavitaton region, which needs a theoretical research breakthrough.At the one part of this thesis, the aerated behaviours in cavitation region of high-velocity flows over surface irregularity---offset into flow are investigated. Velocity Field and pressure Field in cavitation region with different air concentrations were observed in details by using three-dimensional Particle Image Velocimetry in the Hydraulics Laboratory at Zhejiang University of Technology. By studing, the 2D-structure of the cavitation region was investigated. The relationship between Flow velocity distribution and entrained air rate was obtained. And the Variation of pressure and cavitation number with change of air concentration were also obtained. The cavitation noise-abatement was preliminary analysed. Based on the principle of compressible flow, the problems of sound speed and shock waves for high-velocity aerated flow on the order of 50m/s was dealt with in the end of this paper.At the other part of this thesis, marine 0current energy converter is investigated. Marine Current Energy is a kind of clean and renewable energy, which can be used for generating electricity based on the principles similar to those used in wind power generation. The exploitation of marine current energy not only can alleviate the pressure caused by energy resources consuming and adjust the structure of energy resources in china, but also can be beneficial to environment. There is lack of researches on marine current energy at present in this country, so this paper studies on marine current energy conversion system and two different kinds of marine current energy converter were presented, which can increase the output of marine current energy. The findings of this paper can be widely used in power generation of marine current energy, which would effectively help ease the energy crisis in the coastal areas, and provide a broader prospect for exploring and utilizing low-velocity marine current energy.