Motion of a Spherical Gas Bubble in an Oscillatory Pressure Field.

Abstract

An experimental and numerical study on nonlinear radial oscillation of a gas bubble in liquids is presented. In the experimental part of this study, an oscillatory pressure field is generated in a cylindrical cell, which consists of two piezoceramic transducers and a glass cylinder. A new bubble generator is developed. The generator is able to generate a bubble filled with an arbitrary kind of gas. The bubble motion is observed by high-speed photography. The time history of bubble radius is measured from the pictures to compare with the numerical results. The pressure field has a frequency of 19.2 kHz and an amplitude of 40 kPa. The gas in the bubble is air. The bubble has an initial radius within the range from 0.1 mm to 0.25 mm. A highly viscous silicone oil, whose kinematic viscosity is 100 mm2/s, is used for the liquid to keep the spherical shape of the bubble. In the numerical part of this study, the radial motion of a bubble is calculated by using the Keller equation, which is an approximate equation for the bubble motion in a compressible liquid. The Euler equations, in which the thermal diffusion is taken into account, are solved numerically for precisely estimation of the motion of gas in the bubble. A quantitatively good agreement between the experimental and numerical results is obtained in terms of not only radial-time curves but also frequency responses.