Chapter 6 - Introduction to Bubble Dynamics and Cavitation

Abstract

In underwater acoustics, sound propagation may be influenced by the dynamics of suspended gas bubbles in the liquid. If the liquid flows past bodies, cavitation may occur if the static pressure in the fluid decreases below some critical value. Since an understanding of both propagation in bubbly fluids and cavitation requires some knowledge of the dynamics of bubbles; this chapter will examine the dynamics of bubbles; the linear perturbations of gas-filled bubbles by small amplitude pressures, the propagation through bubbly mixtures, the onset of nonlinear large-amplitude bubble motions, and implosive collapses that produce sound. The subject of nonlinear bubble dynamics as covered here is introductory to our coverage of hydrodynamic cavitation inception and noise in the next chapter. Accordingly, we emphasize the basic behavior of air bubbles in water and illustrate the various uses of the theory of single-bubble dynamics in estimating bubble motion and critical pressure for nonlinear growth. We will also show how a related linear modeling of the acoustics of bubble swarms is useful in describing the wave dispersion characteristics in water filled hydrodynamic test environments.