Experimental and theoretical investigation of the mean acoustic pressure in the cavitation field

Abstract

The cavitation field radiated by a 20 kHz sonotrode-type transducer is experimentally and theoretically analyzed. Special interest is paid to the origin of the strong fluid streaming appearing in low frequency sonoreactors. A new experimental procedure is proposed to evaluate the mean acoustic pressure inside the fluid. This parameter has been quantified for different points and amplitudes. The velocity of the radiating surface is controlled by a laser interferometer and is always sinusoidal. Train wave excitation is used. The pressure wave and amplitude are measured in the tank with a calibrated hydrophone. The acoustic mean pressure is estimated from the total pressure value at the end of the pulse after an adequate filtering. An analytical nonlinear second order model based on the coupling of the equations of the fluid mechanics with the Rayleigh-Plesset equation is developed in order to relate the measured acoustic parameters to the cavitation state of the fluid. The distributions of the fundamental amplitude and mean pressure are calculated as a function of bubble density and bubble size. A qualitative theoretical description of the experimental data is presented. Quantitative differences and model limitations are commented.

Two-dimensional Numerical Simulations of Nonlinear Ultrasonic Propagation in Bubbly Liquids

“…This fact has already been observed by the authors in other numerical and experimental works referred to bubbly media [16,9], in particular when waves interferences occur [17,10,13]. The nonlinear bubble vibration strongly affects the distribution of energy in the frequency domain but not the distribution of energy in space, which remains highly concentrated at the focus.…”

Unsteady translation and repetitive jetting of acoustic cavitation bubbles

“…Small bubbles show weak or no volume pulsations and accordingly feel weak and negligible primary Bjerknes forces [3,16]. They are probably advected by bulk (Eckart-type) acoustic streaming [19] away from the tip (downward). From the drift of the smallest discernible bubbles at the resolution limit (≈5 μm) and fluorescent particle tracking [17], acoustic streaming is found to direct downward with speeds from about 0.2 to 0.7 m/s.…”

Ultrasound‐Promoted Reaction of 2‐Chlorobenzoic Acids and Aliphatic Amines

“…If the fre- quency is increased, the production of cavities in the liquid is decreased and therefore the sonochemistry effect is less effective. [28][29][30][31][32] To demonstrate the scope of the ultrasound-assisted method, several 2-chlorobenzoic acids and different primary or secondary amines were used. The results are shown in Table 1.…”