Research On Sound Propagation In Cavitation Cloud

This paper simulates the sound propagation phenomenon in a cavitation cloud by employing the nonlinear wave equation coupled with the bubble dynamic equation to explore the related law and characteristics,focusing on the appearance of frequency gap,on cavitation enhanced heating process during the propagation,on acoustic cavitation of a mixture consisting of two kind of bubbles.When the parameters of cavitation cloud satisfy some certain conditions,there will appear a gap at specific position on frequency spectrum of the sound signal in the cavitation liquid.On weak driving amplitude conditions,the starting position of the frequency gap is consistent with what predicted by the classic linear multiple scattering cases.However,on intense driving amplitude conditions,the frequency gap of some cases disappears even though it did appear for the same case on the weak driving amplitude condition.The current appearance of the gap has a strict requirement for the bubble radius.The spatial distribution of the in-gap frequency acoustic component shows an oscillating cut-off or exponential decay.Based upon the theoretical results,under laboratory conditions,an experiment system was designed and set up to record the acoustic signals of different cavitation condition then observing and analyzing the frequency spectrum characteristic.Guided by the requirements of the theoretical results,much effort was made to find a proper experiment method.Finally,by making a particular experiment liquid environment,we succeeded to capture the same frequency gap.The real cavitation cloud is supposed to consist of bubbles who have different radii.In this paper,simulations of the acoustic cavitation consists of two kind of bubble in a cylindrical container were conducted.The results about the acoustic dissipation absorbing effect of the container wall,about the respective dynamical behavior of each kind of bubbles,about the variation of relative acoustic intensity and mean bubble radius for different bubble proportion were discussed.The results reveal that small bubbles(4.5um)is very sensitive to the existence of large bubbles(30um),and obviously suppressed by big bubbles.The large bubbles dominate the cavitation process.The interactive radiant pressure analysis shows that the acoustic radiation pressure of large bubbles is overwhelmingly stronger than the one of small bubbles.Besides,this paper studied on the cavitation enhanced heating phenomenon.Based upon the discussion about the mechanism for cavitation heating,the viscous dissipation at the interface between liquid and gas is supposed to be very important for the cavitation heating.By analyzing the case for heat production of one individual bubble,this paper shows the relationship between heat production and bubble resonance.Based on heat conduction equation,simulations about the process of one dimension cavitation cloud heating were conducted,discussing the temperature rise and its spatial distribution under different bubble radius and driving amplitude conditions in certain position.The conceptional experiment was conducted to observe the temperature rise under acoustic cavitation.