Thermodynamic Effects on Cavitation in Water and Cryogenic Fluids

Abstract

The present study focuses on the formation of cavitation in cold and hot water and in cryogenic fluid, characterized by strong variations in fluid properties caused by a change in temperature. Cavitation phenomenon is investigated in water and nitrogen flows in a convergent-divergent nozzle through pressure measurements and the optical visualization method. High-speed photographic recordings have been made, the cavitation phenomena evolution and the related frequency content are investigated by means of pixel intensity time series data. The results obtained concur with those obtained with the spectral analysis of the pressure signals. In the case of cryogenic fluid frequency peaks are shifted towards lower frequencies, with respect to cold water and the magnitude of the signal rises, in particular at low frequencies, for nitrogen and hot water. This can be due to thermal effects that contribute also to the low frequencies in the case of cryogenic fluid. To verify the validity of this assumption, a simple model based on the resolution of Rayleigh equation is used.