Fluid Theories

Abstract

The term “fluid theory” is to be interpreted in the nomenclature of Ch. 2. That is, “wave theory,” “propagation theory,” or, simply, “theory,” refer to systems of equations governing wave motion and boundary conditions for sound pressure fields (and related fields) in sediments. The term “theory” is distinct from the term “model” which is reserved for applications of theory (often with simplifying approximations) to produce specific predictions, e.g., of sound scattering. The next three chapters will consider, in order of increasing complexity, fluid, elastic, and poroelastic theories. These theories are required for the scattering and penetration models treated in Chs. 13–15. The acoustic modeler will usually choose the simplest theory that can account for the phenomena evident in the data at hand. Because of the close relationships between the various theories, the discussion of research issues will be unified and placed at the end of Ch. 10.