Propagation modeling issues for macro/micro scale environments

Abstract

The propagations of acoustic signals through a porous solid and through a bubble cloud are both representative of a class of experiments for environments that are observable on macro and micro length scales. Intuitive models for these propagations are described by theories for poroelastic solids and for frothy fluids, respectively. These theories reflect a different intuitive understanding of the underlying physics that applies to the micro scale, and accommodate different phenomenology that can be observed on the macro scale. A more precise understanding of the linkage between micro and macro scale observations is a fundamental problem that has attracted a number of different approaches that are usually left unrelated. Moreover, there are other phenomenology that, while observable on a macro scale, are not modeled by either theory, and other models that are developed for these other phenomenology. An example of another phenomenology is a continuous backscattering occasioned by micro scale heterogeneity, which results in a kind of localization in one dimension. An example of another model is a radiative transport model. These issues are discussed in the light of still another approach to accommodating macro/micro scale variation, this one based on a phase space, spatial filtering. [Work supported by ONR.]