An experimental investigation on erosive partial cavitation has been carried out based on the measurement of cavitation induced vibrations in a broadband frequency range up to 100 kHz. The use of acceleration transducers mounted on the test section is valid to study the physical characteristics of this type of cavitation. The analysis of the vibrations spectral content and the amplitude demodulation of the acceleration signals filtered from 45 kHz to 50 kHz permits us to quantify the cavitation intensity and to identify the main cavity shedding frequency. A series of tests have been carried out with sheet (stable) and cloud (unstable) cavitation regimes using the NACA 65012 hydrofoil corresponding to incidence angles of 4 deg and 6 deg, respectively. In each regime, cavity lengths of about 20 % and 40 % of the chord have been reproduced at various free stream velocities from 15 m/s to 30 m/s. The shedding process of cloud cavitation follows a constant Strouhal value based on the main cavity length of about 0.28, meanwhile, for sheet cavitation it follows a constant value of about 0.16. At low free stream velocities, no modulation is detected for sheet cavitation When the length of the mam cavity is reduced from 40 % to 20 % of the chord, the modulation frequency peak is lowered and widened out The intensity of the erosive partial cavitation has been measured based on the mean square acceleration of the modulation frequency peak The effect of increasing the flow free stream velocity has been well quantified for cloud cavitation In particular, the intensity shows a power law dependency on the velocity with an exponent of about 6.7. A good correlation has also been found between the modulation level and the actual average pitting rate measured on the hydrofoil stainless steel samples for cloud cavitation.
Dynamics and intensity of erosive partial cavitation
Dynamik und Intensität partieller erosiver Kavitation
Transactions of the ASME, Series I. Journal of Fluids Engineering ; 129 , 7 ; 886-893
2007
8 Seiten, 13 Bilder, 1 Tabelle, 19 Quellen
Article (Journal)
English
High Speed Video Observations and Erosive Cavitation
British Library Conference Proceedings | 2004
|AIAA | 1983
|AIAA | 1986
|AIAA | 2003
|Solid propellant erosive burning
AIAA | 1987
|