Sound Speed and Attenuation in Multiphase Media
Final rept. 1 Feb 2004-31 Mar 2011
BOSTON UNIV MA DEPT OF MECHANICAL ENGINEERING
Pagination or Media Count:
This report discusses an investigation of the sound speed and attenuation in multiphase media, sandy and muddy sediments, that has shown that a simplified-Biot theory adequately predicts the sound speed and attenuation in sandy sediments with porosities of less than 65. In addition for muddy sediments with porosities of greater than 70 mixture theory can describe the sound speed. This report discusses the experimental and theoretical basis for these conclusions and related this investigation to other contemporary ONR sponsored research projects. A key finding is the conclusion that in waveguides with a sandy boundary that the effective attenuation obeys a power law with an exponent of 1.8 as proposed by Rosenfeld 2001 and Holmes 2007. Theory predicted a quadratic dependence, exponent of 2. This research has shown that energy removed by shear wave conversion explains this difference, that is the exponent of 1.8 compared to 2. Finally a card house theory was developed to explain the properties of high porosity muddy sediments and that a Mallock-Wood mixture equation describes the slow sound speed.
- Physical and Dynamic Oceanography