J. C. Ryu
Mech. Eng. Dept., Chung-Ang Univ., Seoul 156-756, Korea
Ohsan Tech. College, Ohsan 447-749, Korea
Gas bubble behavior immersed in liquid under a high-intensity ultrasonic field was studied by using a self-consistent model. In this model, the temperature distribution of the gas inside the bubble was obtained by solving analytically the continuity and energy equations for the gas. Also heat transfer between the gas inside the bubble and the surrounding liquid was considered by solving the mass, momentum, and energy equation for the liquid. With this model, the polytropic approximation is no longer required to calculate the internal pressure of the oscillating bubble under ultrasonic field. Under the periodic ultrasonic field with an amplitude of 110 kPa and a frequency of 20 kHz, the temperature of air at the bubble center with equilibrium radius of 20 (mu)m reached as high as 5000 K at the time of bubble collapse. The heat flux from the bubble to the surrounding fluid by conduction is above 10 MW/m[sup 2] at this stage. The pressure inside the bubble at this stage is about 10 bar, which is much less than that obtained by a previous model. Calculation results support the hot spot theory, which states that the phenomenon of sonoluminescence is due to chemiluminescence by the high temperature of gas inside the bubble.