Experimental measurements of surface stiffness on water-saturated porous solids

Journal Article · Tue Feb 01 04:00:00 EST 1994 · Journal of the Acoustical Society of America; (United States)

DOI:https://doi.org/10.1121/1.408393· OSTI ID:5434613

Nagy, P B; Blaho, G ^[1]

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1. Department of Welding Engineering, The Ohio State University, Columbus, Ohio 43210 (United States)

The surface impedance of a fluid/fluid-saturated porous solid interface is defined as the ratio of the pressure difference between the fluids on the two sides of the interface and the volume velocity of the fluid through the surface pores. In most cases, the surface pores are inherently open'' and the surface impedance is negligible when the sample is fully submerged in fluid. On the other hand, due to surface tension, practically closed-pore boundary conditions can prevail at an interface between a nonwetting fluid (e.g., air) and a porous solid saturated with a wetting fluid (e.g., water). This effect is caused by the high stiffness of the microscopic fluid membranes extended by capillary forces over the otherwise open surface pores. We have determined the quasistatic surface stiffness of different water-saturated porous materials by changing the hydrostatic pressure and directly measuring the average surface displacement by an acoustical sensor. Generally, the surface stiffness is proportional to the surface tension of the wetting fluid and inversely proportional to the static permeability of the specimen. For cylindrical pores, the measured surface stiffness is in good agreement with theoretical predictions. For more irregular geometries, such as consolidated spherical beads, the surface stiffness is still inversely proportional to the static permeability but its value is orders of magnitudes lower than for cylindrical pores of comparable permeability.

• DOE Contract Number: FG02-87ER13749
• OSTI ID: 5434613
• Journal Information: Journal of the Acoustical Society of America; (United States), Journal Name: Journal of the Acoustical Society of America; (United States) Vol. 95:2; ISSN 0001-4966; ISSN JASMAN
• Country of Publication: United States
• Language: English

Related Subjects

661300* -- Other Aspects of Physical Science-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BOUNDARY CONDITIONS
IMPEDANCE
INTERFACES
MATERIALS
MECHANICAL IMPEDANCE
PERMEABILITY
POROUS MATERIALS
SATURATION
SOUND WAVES
SURFACE PROPERTIES
SURFACE TENSION
WATER SATURATION