The Influence Of The Gradient Multi-index And Different Excitation Sound Fields On The Single Bubble Cavitation Motion

In this paper, an expression of the gaseous polytrophic index with the variation of the velocity of bubble wall is put forward. This expression can be applied into the R-P equation of the single bubble dynamics. Then, the solution of the R-P equation with gradient index and adiabatic condition is obtained by numerical calculation. The numerical results of the modified R-P equation are fitted well with the experimental data when the results are compared with the experimental results. Especially in the first expansion period, the results are better than the R-P equation under adiabatic condition. Comparing with the cavitation bubble motion equation at adiabatic state with different sound pressure amplitude, initial radius, frequency, the simulation results show that: when the sound signal is in the low frequency band, the sound pressure amplitude near the cavitation threshold, and the initial radius is quite small, these two kinds of numerical simulation results are quite different, so the process of cavitation bubble can not be considered as an adiabatic process; the bigger the sound pressure amplitude, the greater the initial radius and the higher the frequency, these two kinds of numerical simulation results are more similar, which means the cavitation bubble cavitation process is closer to adiabatic process.The motion of bubble with different sound signals is numerically simulated Based on the R-P equation. The main work and conclusions are as followed:(1) The cavitation bubble motion with the excitation of the single frequency sinusoidal signal is analyzed. The results show that there is an optimal initial phase that can enhance the collapse of bubble.(2) The cavitation bubble motion with the excitation of the signal which composed of fundamental wave and higher harmonic is analyzed. It is found that the composed signal can effectively enhance the bubble cavitation, and there are an optimal sound pressure amplitude ratio and initial phase enhancing the process.(3) The cavitation bubble motion with the excitation of the signal which composed of fundamental wave and half wave sine wave is analyzed. It is found that the composed signal can effectively enhance the bubble cavitation(4) The cavitation bubble motion with the excitation of rectangular wave is analyzed. In the case of the same frequency and sound pressure amplitude, the bubble cavitation under square wave excitation is more severe, and the larger the duty ratio, bubble collapse is fiercer when compared with the sine wave. But when the duty ratio reaches a certain value, bubbles will no longer crash.(5) The cavitation bubble motion with the excitation of the saw tooth wave is analyzed. In the case of the same frequency and sound pressure amplitude, the collapse of bubble is greatly enhanced under the excitation of the sawtooth wave when compared with the sine wave.