Cavitation-induced vibration and erosion of pipes is a potentially damaging factor in piping systems. To prevent it, a detection method for cavitation phenomena should be developed. In power plants, especially, it is desirable to detect them from outside pipes during operation. Detection of cavitation phenomena was experimentally investigated in this paper using accelerometers mounted on the outer surface of a pipe upstream and downstream from an orifice. The following results were obtained. (1) With the progression of cavitation, output voltage of the accelerometer varied, and the amplitude and number of the pulse-shaped signals increased. However, it would likely be difficult to distinguish them from noises in an operating plant. (2) It was difficult to recognize the characteristic frequency of cavitation, because the power spectrum density was broad up to the accelerometer limit of 45 kHz. (3) The flow directional distribution of RMS (root mean square) values of accelerometer output voltage varied greatly with the progression of cavitation. Therefore, from comparison of RMS values obtained upstream and downstream from the orifice it seems possible to detect cavitation phenomena in the piping systems of operating plants.

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An experimental study is presented on the erosion process caused on the target specimens by solid particle impingement, in which precise quantifications are given as to the dependencies on collision angle and collision velocity. In order to eliminate fluid-dynamic drag force that retards the particles' motion before they impinge upon the targets, the experiments are performed in the vacuum vessel. In the process of erosion, the existence of so-called incubation period is confirmed. Measured exponents of the velocity are considerably smaller than those for the handy application and are rather close to semi-theoretical values of Bitter and Finnie, which suggests that they can be used in the numerical prediction. Regarding the dependency on collision angle, it was found clear discrepancy between the experimental results and predicted one by means of models of Bitter and Finnie as the collision angle increased. For the spherical particles, the cutting erosion actually ceases before the collision angle becomes normal.

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An experimental study is presented on the erosion process caused on the target specimens by solid particle impingement, in which precise quantifications are given as to the dependencies on collision angle and collision velocity. In order to eliminate fluid-dynamic drag force that retards the particles' motion before they impinge upon the targets, the experiments are performed in the vacuum vessel. In the process of erosion, the existence of so-called incubation period is confirmed. Measured exponents of the velocity are considerably smaller than those for the handy application and are rather close to semi-theoretical values of Bitter and Finnie, which suggests that they can be used in the numerical prediction. Regarding the dependency on collision angle, it was found clear discrepancy between the experimental results and predicted one by means of models of Bitter and Finnie as the collision angle increased. For the spherical particles, the cutting erosion actually ceases before the collision angle becomes normal.