Erosion of a Copper Rod in a Light Emission Flow of an Orifice Cavitation

Cavitation bubbles emit very weak light (luminescence) due to the bubble collapses. It is expected that the light emission may be closely related to the cavitation erosion. In order to confirm the relationship between the erosion damage rate and the luminescence intensities, erosion tests are performed for a water orifice cavitation flow in a circular pipe. In the experiments, a unique method of erosion test is used to prevent a secondary occurrence of cavitations, that is, a copper rod polished like a mirror is put on the central axis of the circular pipe from the upstream side of the orifice to the downstream side. The damage rate is estimated by counting the number of damage pits, and the luminous intensity is measured by a photon counter. The image of the cavitation light emission is also taken by an image intensifier. It is shown that the profile of the damage rate is shifted marginally downstream from the profile of emission intensity, though their positions are within the region of the pressure recovery, and that the maximum damage rate has a strong relationship with the maximum emission intensity.