| The stability of cavitation bubble interface could be affected by the external acoustic field which is important to the hydraulic turbines,noise control and biomedical applications.For example,when a bubble collapses near the solid wall,the jet of the bubble will damage the surface.During the expansion and shrinkage of the bubble,a large pressure wave will be generated,causing the deteriorate operation of the hydraulic mechinery through the modification of the local or the global flow.There are four kinds of the stability mechanisms of the bubble oscillation:spherical stability,stiffness stability,diffusional stability and positional stability.The present paper focuses on the staibility relating with the first three mechanisms.In the literature,the bubble stability status and the related rectified mass diffusion process has not been clearly given.The present paper focuses on the oscillation and stability status of the complex cavity in Newtonian liquids.Firstly,we derived a complete equation of bubble motion with the consideration of the mass transfer and the liquid compressibility.Based on the perturbation method,the bubble motion equation is modified and we obtained quantitative contributions of the different damping mechanisms(e.g.viscous damping,thermal damping,acoustic damping and mass damping).The results show that effect of mass transfer is quite influential on the determination of the polytropic exponent,natural frequency and energy dissipation.Secondly,the present paper discussed the stability status of vapor and vapor-gas bubbles governed by the spherical and the stiffness mechanisms together with the critical values.The influential factors include the acoustic frequency,bubble radius,gas content and liquid temperature,etc.The critical pressure amplitudes of spherical stability of a bubble will be converged at fixed values in the condition of high-frequency or low-frequency limits.Finally,the present paper studies the stability status of a gas bubble affected by the rectified mass diffusion and its influential factors(e.g.gas concentration,equilibrium bubble,and acoustic frequency).The high acoustic excitation frequency will lead to the stability status moving towards the small-radius and the large-pressure-amplitude zone. |
