Recent research in cavitation erosion has been mainly aimed at discovering the correlations with other macroscopic phenomena to be used as efficient monitors of the inception and intensity of erosion (Lush, 1986, ITTC, 1987 and 1990). The first step consisted in the adoption of an efficient descriptor of the erosion intensity. To this end, cumulative mass loss, mass loss rate, erosion 'intensity', erosion 'strength', mean depth penetration rate and surface density of pits have been progressively introduced. Then, the correlations were searched between the erosion intensity and the characteristics of the fluid flow, where applicable, or with other phenomena characteristic of cavitation, i.e. noise (global or spectral components), electrochemical current intensity and sonoluminescence intensity. Many studies have been devoted to the use of noise as a monitor of erosion. This was suggested by the ease of noise measurements at different testing conditions and to the unwanted effects produced by noise itself, especially in ship propulsion. As regards the use of electrochemical current, which is the basis for the DECER cavitation detector, some experimental results [4] indicate that the electrochemical potential difference during cavitation is one order of magnitude larger than the potential difference excited by the ultrasound only. Only a few studies refer to the use of sonoluminescence. Among these, Van der Meulen (1986) concludes that further research is needed to clarify the correlation between sonoluminescence and erosion intensities. Acoustic signals or sonoluminescence correlate in fact with the collapse intensity of cavitation bubbles, but not always with the severity of erosion. This paper concerns experiments performed in a vibratory cavitation rig where a stationary aluminum specimen is subjected to an ultrasonic beam. Aluminum has been chosen since this metal has often been considered with interest in the cavitation erosion literature. With a mind also to underwater applications, the tests have been conducted with hydrostatic pressure as a parameter.
Experimental Study of Some Electrochemical Effects Connected with Cavitation
FRANCESCUTTO, ALBERTO;
1994-01-01
Abstract
Recent research in cavitation erosion has been mainly aimed at discovering the correlations with other macroscopic phenomena to be used as efficient monitors of the inception and intensity of erosion (Lush, 1986, ITTC, 1987 and 1990). The first step consisted in the adoption of an efficient descriptor of the erosion intensity. To this end, cumulative mass loss, mass loss rate, erosion 'intensity', erosion 'strength', mean depth penetration rate and surface density of pits have been progressively introduced. Then, the correlations were searched between the erosion intensity and the characteristics of the fluid flow, where applicable, or with other phenomena characteristic of cavitation, i.e. noise (global or spectral components), electrochemical current intensity and sonoluminescence intensity. Many studies have been devoted to the use of noise as a monitor of erosion. This was suggested by the ease of noise measurements at different testing conditions and to the unwanted effects produced by noise itself, especially in ship propulsion. As regards the use of electrochemical current, which is the basis for the DECER cavitation detector, some experimental results [4] indicate that the electrochemical potential difference during cavitation is one order of magnitude larger than the potential difference excited by the ultrasound only. Only a few studies refer to the use of sonoluminescence. Among these, Van der Meulen (1986) concludes that further research is needed to clarify the correlation between sonoluminescence and erosion intensities. Acoustic signals or sonoluminescence correlate in fact with the collapse intensity of cavitation bubbles, but not always with the severity of erosion. This paper concerns experiments performed in a vibratory cavitation rig where a stationary aluminum specimen is subjected to an ultrasonic beam. Aluminum has been chosen since this metal has often been considered with interest in the cavitation erosion literature. With a mind also to underwater applications, the tests have been conducted with hydrostatic pressure as a parameter.Pubblicazioni consigliate
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