The Scattering of Flexural Waves from a Coated Cylindrical Anomaly in a Thin Plate
by
Vernon A Squire
University of Otago
Coauthors: Tony W Dixon

Early scattering theory models of the Marginal Ice Zone (MIZ) based on an extension of single floe scattering to the entire ice field do not match field observations perfectly. However, recent advances in the scattering theory of electromagnetic and acoustic waves passing through random media have demonstrated excellent agreement with experiment, despite the fact that microscale phenomena are being extended to the macroscale. With this in mind we have initiated efforts to apply these techniques to the MIZ. By treating the MIZ as a discrete random medium (an analogue of a material with two different dielectric constants), we are attempting to construct a fictitious continuum effective medium that incorporates the multiple-scattering behaviour of the real random medium to first order. To find the effective medium as a function of wave number we will focus on a single scatterer (ice floe) that we `coat' with some of the background medium (water). The size of the coating is dependent on the concentration of the scatterers. This new scattering unit (coated scatterer) is then embedded in an effective medium that replaces the remainder of the random medium. The properties of the effective medium can then be determined by allowing a plane wave to impinge on the coated scatterer using an appropriate criterion. Unfortunately, no random medium theory exists for flexural wave motion through an elastic plate (our model for a single ice floe) as governed by the Euler-Bernoulli equation and, accordingly, we have proceeded to develop the theory ourselves. We are first considering the scattering of pure flexural waves in an elastic plate, disregarding the presence of ocean waves for the moment. To apply the theory to an example we have solved a simple matching problem, namely plane waves impinging on a single coated cylindrical anomaly in a thin plate. The talk will discuss this solution.

Date received: June 17, 1999

Copyright © 1999 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # cacc-49.