Study of Relationship between Cavitation Light Emission and Erosion in an Orifice Flows

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A relationship between the light emission of an orifice cavitation flow and the caviation erosion is investigated. A very weak light emission can be found in the cavitation flow. For the visualization of the light emission pattern in the flow, CT technique in which Abel transformation is modified is applied. The experiment is systematically performed by changing the conditions of the upstream pressures and orifice diameters. Empirical formula for the cavitation emission intensity is obtained. The damage rate of the cavitation erosion is also measured by a new experiment system, where a copper rod is placed on the axis of the tube through an orifice hole. It is found that the position of cavitation damage slightly deviates from the position of light emission. But the maximum cavitation damage rate strongly relates to the maximum emission intensity. In order to verify the above results in the more complex flow, a similar research is also advanced for the cavitation generated around the c … More ylindrical column on the flat plateThe light emission in the orifice cavitation occurs easily, but it is influenced by the flow pattern and bubble distributions. Hence, a unique experimental method using a water hammer is proposed. The device can generate very high pressure of a water hammer of about 100 atm, The bubbles are instantaneously compressed by the pressure. Then a fairly strong light emission occurs in a tube. It is clarified that the light emission accurately progresses with the shock front of the water hammer. This result is expected to be utilized for the detection of a water column separation in a piping system. Theoretical calculation of a single bubble behavior is performed for the estimation of emission intensity. A theoretical prediction of emission intensity is constructed by using the equilibrium radiation theory considering the ionization and recombination of the atom. Calculation result shows that the light emission is strongly effected not only by the thermal conductivity but also by the ionization energy. Less