High-Speed Video Observations and Acoustic-Impact Measurements on a NACA 0015 Foil

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

“…A similar explanation was recently suggested by van Rijsbergen et al [1]. Based on acoustic emission measurements they came to a conclusion -that only cloud implosions where the emitted shock wave has a clear orientation (the highest impact occurs when the wave front is directed toward the wall) lead to stress on the surface and erosion.…”

“…However, obviously, many questions remain open. Recent studies by van Rijsbergen et al [1] and Petkovsek and Dular [2] hypothesized that it is either (i) that the number and the distribution of the single bubbles in the vicinity of the wall have a mayor role in the process of cavitation erosion or (ii) that the shock waves that originate from the cloud collapse are not perfectly spherical and have a clear orientation -the highest impact occurs when the wave front is directed toward the wall. The original motivation behind the present study was to gain a more in-depth knowledge of the process and the either confirm or deny the mentioned hypotheses.…”

“…Foeth et al [7] have shown that the cloud cavitation that is associated with the break up of sheet cavitation is essentially an organized mixture of cavitating vortices. Boorsma and Whitworth [8] and van Rijsbergen et al [1] related the structures to the acoustic emission signals and suggested that the orientation of the shock wave should be considered. Large scale primary spanwise vortices were studied by Pereira et al [9] and Kawanami et al [10], who observed their development by stereography and holography, respectively.…”

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a b s t r a c tRecently 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.

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Experimental and Numerical Investigation of the Cavitating Flows over a Modified NACA0009 Foil

“…They concluded that the collapse of the cloud cavitation structures is responsible for 80 percent of the erosion damage. Van Rijsbergen et al [3] used high-speed visualization, paint test, and acoustic measurement to investigate the behavior of the cavitating flow over a NACA0015 foil with the aim to identify the role of different cavitating structures in the cavitation erosion. Similar to Dular and Petkovsek [2], they found that the collapse of cavitating cloudy structures is associated with high risk of cavitation erosion.…”