Modeling The Drag Forces Of Porous Media Acoustics
Name
1992.5 Pride.pdf
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863.51 KB
Format
Adobe PDF
Checksum (MD5)
b566d8798d126dd6ba45a7fae5ed91e7
Author(s)
Pride, Steve
Date Issued
1992
Publisher
Massachusetts Institute of Technology. Earth Resources Laboratory
Series/Report no.
Earth Resources Laboratory Industry Consortia Annual Report;1992-05
Abstract
The drag forces controlling the amount of relative flow induced in a fluid-saturated
porous material by a mechanical wave are modeled here from first principles. Specifically, analytical expressions are derived for the drag force in material models that possess variable-width pores; Le., pores that have widths that vary with distance along their axis. The dynamic (complex, frequency-dependent) permeability determined for
such a variable-width pore model is compared to estimates made using the models of
Johnson, Koplik, and Dashen (JKD) and of Biot. Both the JKD model and the Biot
model underestimate the imaginary part of the dynamic permeability at low frequencies
with the amount of discrepancy increasing with the severity of the convergent/divergent
flow; Le., increasing with the magnitude of the maximum pore-wall slope relative to
the channel axis. It is shown how to modify the JKD model to obtain proper low-frequency
behavior; however, even with this modification, discrepancies still exist near
the transition frequency that separates viscous-force-dominated flow from inertial-force-dominated flow. The amount of discrepancy is again a function of the severity of the
convergent/divergent flow (maximum pore-wall slope).
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