On the mechanisms of cavitation erosion – Coupling high speed videos to damage patterns.

Recently van Rijsbergen et al. (2012), by simultaneous observation of cavitation and acoustic emission measurements, and Petkovsek and Dular (2013), by simultaneous observation of both cavitation structures and cavitation damage, have pointed to the fact that the small scale structures and the topology of the cavitation clouds play a significant role in cavitation erosive potential. Despite the two, before mentioned, studies opened some new insights to the physics of cavitation damage, many new questions appeared. In the present study we attached a thin aluminum foil to the surface of a transparent Venturi section using two sided transparent adhesive tape. The surface was very soft – prone to be severely damaged by cavitation in a very short period of time. Using high speed cameras, which captured the images at 30,000 frames per second, we simultaneously recorded cavitation structures (from several perspectives) and the surface of the foil. Analysis of the images revealed that five distinctive damage mechanisms exist – spherical cavitation cloud collapse, horseshoe cavitation cloud collapse, the “twister” cavitation cloud collapse and in addition it was found that pits also appear at the moment of cavitation cloud separation and near the stagnation point at the closure of the attached cavity. [ABSTRACT FROM AUTHOR]