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Further experimental studies of area suction for the control of the laminar boundary layer on a porous bronze NACA 64A010 airfoil

Description: Report presenting a low-turbulence wind-tunnel investigation of an NACA 64A010 airfoil with a porous surface to determine the reduction in section total-drag coefficient that can be obtained at large Reynolds numbers by using area suction. While previous testing has been reported on, the focus of this paper is primarily the results of additional tests of the same airfoil model equipped with a porous skin of lower porosity.
Date: May 1950
Creator: Braslow, Albert L. & Visconti, Fioravante
Partner: UNT Libraries Government Documents Department

An experimental study of porosity characteristics of perforated materials in normal and parallel flow

Description: Report presenting an experimental investigation to determine the porosity characteristics of perforated materials for normal and parallel flow. The results indicated that the porosity of the material is primarily governed by its open ratio, but that density has a slight effect. When the material was tested under parallel-flow conditions, the effective porosity dropped markedly as the stream velocity increased.
Date: November 10, 1953
Creator: Stokes, George M.; Davis, Don D., Jr. & Sellers, Thomas B.
Partner: UNT Libraries Government Documents Department

An experimental study of porosity characteristics of perforated materials in normal and parallel flow

Description: Report presenting an experimental investigation to determine the porosity characteristics of perforated materials in normal and parallel flow. The results indicted that the porosity of material is governed principally by its open ratio, but that density has a slight effect.
Date: April 1954
Creator: Stokes, George M.; Davis, Don D., Jr. & Sellers, Thomas B.
Partner: UNT Libraries Government Documents Department

Pressure diffusion waves in porous media

Description: Pressure diffusion wave in porous rocks are under consideration. The pressure diffusion mechanism can provide an explanation of the high attenuation of low-frequency signals in fluid-saturated rocks. Both single and dual porosity models are considered. In either case, the attenuation coefficient is a function of the frequency.
Date: April 8, 2003
Creator: Silin, Dmitry; Korneev, Valeri & Goloshubin, Gennady
Partner: UNT Libraries Government Documents Department

Experimental and theoretical studies of area suction for the control of the laminar boundary layer on an NACA 64A010 airfoil

Description: From Summary: "A low-turbulence wind-tunnel investigation was made of an NACA 64A010 airfoil having a porous surface to determine the reduction in section total-drag coefficient that might be obtained at large Reynolds numbers by the use of suction to produce continuous inflow through the surface of the airfoil (area suction). In addition to the experimental investigation, a related theoretical analysis was made to provide a basis of comparison for the test results."
Date: March 30, 1951
Creator: Braslow, Albert L.; Burrows, Dale L.; Tetervin, Neal & Visconti, Fioravante
Partner: UNT Libraries Government Documents Department

Geological Survey Investigations in the U12b.02 Tunnel, Nevada Test Site

Description: From introduction: The papers comprising the various parts of this report contain the preliminary results of the U. S. Geological Survey investigations in the U12b.02 tunnel at the Nevada Test Site.
Date: October 1958
Creator: Diment, William H.; Wilmarth, V. R.; McKeown, F. A.; Dickey, D. D.; Wilcox, R. E.; Botinelly, Theodore et al.
Partner: UNT Libraries Government Documents Department

GENERIC THERMO-MECHANICAL MODEL FOR JOINTED ROCK MASSES

Description: A new nonlinear thermo-mechanical model for heavily jointed rock masses is presented. The model uses correlation functions between the porosity and the basic rock properties such as elastic moduli, tensile and compressive strength. The model assumes that the media is isotropic and is characterized by two variable parameters: insipient porosity and in-situ-to-intact modulus ratio.
Date: March 8, 2007
Creator: Vorobiev, O
Partner: UNT Libraries Government Documents Department

Geological Survey Investigations in the U12b.01 Tunnel, Nevada Test Site

Description: From introduction: This report includes a brief description of the stratigraphy and structure, and data on petrology, mineralogy, and chemical and physical properties of the rocks that are exposed in the U12b.01 tunnel of the U12b (Rainier) tunnel system.
Date: March 1959
Creator: Diment, William H.; Wilmarth, V. R.; McKeown, F. A.; Dickey, D. D.; Botinelly, Theodore; Hinrichs, E. Neal et al.
Partner: UNT Libraries Government Documents Department

Laboratory measurements of compressional and shear wave speeds through methane hydrate

Description: Simultaneous measurements of compressional and shear wave speeds through polycrystalline methane hydrate have been made. Methane hydrate, grown directly in a wave speed measurement chamber, was uniaxially compacted to a final porosity below 2%. At 277 K, the compacted material's compressional wave speed was 3650 {+-} 50 m/s. The shear wave speed, measured simultaneously, was 1890 {+-} 30 m/s. From these wave speed measurements, we derive Vp/Vs, Poisson's Ratio, bulk, shear and Young's moduli.
Date: October 25, 1999
Creator: Durham, W B; Waite, WF; Pinkston, J C; Stern, L A; Kirby, S H; Helgerud, M B et al.
Partner: UNT Libraries Government Documents Department

A TIME-DEPENDENT METHOD FOR CHARACTERIZING THE DIFFUSION OF RADON-222 IN CONCRETE

Description: The porosity and diffusion length of concrete have been determined by measuring the time-dependent diffusion of radon through a thin slab of the material, One surface of the slab is exposed to a large, fixed radon concentration beginning at t=0. The radon that diffuses out of a portion of the opposite surface is collected during several contiguous time intervals. The total activity collected over a set of intervals beginning at t=0 and the steady-state flux of activity are used to calculate the porosity and diffusion length, As a test of these parameters, they are then used to predict the activity collected during other time intervals and for other sample thicknesses, Samples from two types of concrete were tested: one type yielded a porosity of 0.068 and a diffusion length of 12.6 cm; the respective values for the other were 0.32 and 16.9 cm. The predicted and experimental results agreed well, thereby verifying the assumption that concrete may be treated as a homogenous diffusion medium for radon.
Date: July 1, 1981
Creator: Zapalac, Geordie H.
Partner: UNT Libraries Government Documents Department

THE EFFECT OF MAGNETICALLY ALIGNED POWDER ON THE MAGNETOSTRICTION OF SINTERED RARE EARTH-IRON LAVES PHASE COMPOUNDS

Description: A powder metallurgical approach is utilized to prepare grain oriented Laves phase compounds of Tb{sub x}Dy{sub 1-x}Fe{sub 2}. The magnetostrains observed in the oriented compounds, though containing {approx}20% porosity as presently prepared, are far superior to those of arc cast and highly dense liquid phase sintered materials. Also, it is shown that the alignment achieved is strongly dependent on the Tb/Dy ratio.
Date: October 1, 1977
Creator: Malekzadeh, M. & Pickus, M.R.
Partner: UNT Libraries Government Documents Department

Poroelastic measurement schemes resulting in complete data sets for granular and other anisotropic porous media

Description: Poroelastic analysis usually progresses from assumed knowledge of dry or drained porous media to the predicted behavior of fluid-saturated and undrained porous media. Unfortunately, the experimental situation is often incompatible with these assumptions, especially when field data (from hydrological or oil/gas reservoirs) are involved. The present work considers several different experimental scenarios typified by one in which a set of undrained poroelastic (stiffness) constants has been measured using either ultrasound or seismic wave analysis, while some or all of the dry or drained constants are normally unknown. Drained constants for such a poroelastic system can be deduced for isotropic systems from available data if a complete set of undrained compliance data for the principal stresses are available - together with a few other commonly measured quantities such as porosity, fluid bulk modulus, and grain bulk modulus. Similar results are also developed here for anisotropic systems having up to orthotropic symmetry if the system is granular (i.e., composed of solid grains assembled into a solid matrix, either by a cementation process or by applied stress) and the grains are known to be elastically homogeneous. Finally, the analysis is also fully developed for anisotropic systems with nonhomogeneous (more than one mineral type), but still isotropic, grains - as well as for uniform collections of anisotropic grains as long as their axes of symmetry are either perfectly aligned or perfectly random.
Date: November 20, 2009
Creator: Berryman, J.G.
Partner: UNT Libraries Government Documents Department

Porous ceramic scaffolds with complex architectures

Description: This work compares two novel techniques for the fabrication of ceramic scaffolds for bone tissue engineering with complex porosity: robocasting and freeze casting. Both techniques are based on the preparation of concentrated ceramic suspensions with suitable properties for the process. In robocasting, the computer-guided deposition of the suspensions is used to build porous materials with designed three dimensional (3-D) geometries and microstructures. Freeze casting uses ice crystals as a template to form porous lamellar ceramic materials. Preliminary results on the compressive strengths of the materials are also reported.
Date: March 15, 2008
Creator: Saiz, Eduardo; Munch, Etienne; Franco, Jaime; Deville, Sylvain; Hunger, Phillip; Saiz, Eduardo et al.
Partner: UNT Libraries Government Documents Department

Pore-fluid effects on seismic waves in vertically fractured earth with orthotropic symmetry

Description: For elastically noninteracting vertical-fracture sets at arbitrary orientation angles to each other, a detailed model is presented in which the resulting anisotropic fractured medium generally has orthorhombic symmetry overall. Some of the analysis methods and ideas of Schoenberg are emphasized, together with their connections to other similarly motivated and conceptually related methods by Sayers and Kachanov, among others. Examples show how parallel vertical-fracture sets having HTI (horizontal transversely isotropic) symmetry transform into orthotropic fractured media if some subsets of the vertical fractures are misaligned with the others, and then the fractured system can have VTI (vertical transversely isotropic) symmetry if all of the fractures are aligned randomly or half parallel and half perpendicular to a given vertical plane. An orthotropic example having vertical fractures in an otherwise VTI earth system (studied previously by Schoenberg and Helbig) is compared with the other examples treated and it is finally shown how fluids in the fractures affect the orthotropic poroelastic system response to seismic waves. The key result is that fracture-influence parameters are multiplied by a factor of (1-B), where 0 {le} B < 1 is Skempton's second coefficient for poroelastic media. Skempton's B coefficient is itself a measurable characteristic of fluid-saturated porous rocks, depending on porosity, solid moduli, and the pore-fluid bulk modulus. For heterogeneous porous media, connections between the present work and earlier related results of Brown and Korringa are also established.
Date: May 15, 2010
Creator: Berryman, J.G.
Partner: UNT Libraries Government Documents Department

The minimum pore size obtainable in a silica gel during drying

Description: The pore size r{sub p} in a gel is determined by the extent of shrinkage of the gel network during drying. Shrinkage is driven by the collapse of the gel network in response to the capillary pressure P{sub c} exerted by the pore fluid. The extent of shrinkage depends on the balance between the capillary pressure P{sub c} in the pore fluid and the bulk modulus K{sub p} of the gel. The hydraulic pore radius, r{sub H} = 2V{sub p}/S{sub a}, where V{sub p} is the pore volume and S{sub a} is the apparent N{sub 2} BET surface area, is often used to characterize the pore size of a gel. A series of acid catalyzed silica gels dried in pore fluids with different {gamma}{sub lv}, showed that there is a limit to the minimum apparent r{sub H} obtainable in a gel, and when the volume fraction of porosity {phi} {le} 0.37, r{sub H} becomes constant and {approximately}0.8 nm. In contrast, experimental data show that the true pore size r{sub p} of gels continues to decrease when {phi} {le} 0.37. Analysis of their adsorption isotherms show that while r{sub H} apparently stays constant: (a) the BET C constant continues to increase, (b) the width and average of their pore size distributions continue to decrease, and (c) as shrinkage continues the gels eventually become non-porous to N{sub 2} at 77K but are still porous to CO{sub 2} at 273K. This paper reviews these results and addresses micropore formation in silica gels with the goal of determining how P{sub c} influences the final r{sub p}, and why r{sub p} and r{sub H} diverge when {phi} {le} 0.37.
Date: December 1994
Creator: Wallace, S.; Brinker, C. J. & Smith, D. M.
Partner: UNT Libraries Government Documents Department

Stress Isotherms of Porous Thin Materials: Theoretical Predictitions From a Nonlocal Density Functional Theory

Description: Recent beam bending (BB) experiments of microporous t31rns with very small pores have shown that the fluid confined in these pores exhibits monotonic compressive stresses as the relative pressure is varied from vacuum to saturation (relative vapor pressure, p/p. = 1). The variation of the stress near saturation is found to be linear in hz(p) and given by the saturated liquid density to within 20%. Capillary condensed fluids are traditionally described by the Laplace-Kelvin (LK) theory. LK theory correctly predicts the slope of the stress near saturation to be pl, but also predicts that the stress should be zero at saturation and tensile between saturation aud the capillary transition pressure. Hence LK theory does not capture the monotonic compressive stress observed in BB experiments. This report describes the results of density functional theory calculations for a simple fluid continued to a slit pore network. We show how the presence of even a small amount of polydispersity in pore size leads to both a monotonic compressive stress as well as the observed LK slope.
Date: November 11, 1998
Creator: Frink, L.J.D. & van Swol, F.
Partner: UNT Libraries Government Documents Department

Estimates of frequency-dependent compressibility from a quasistatic double-porosity model

Description: Gassmann's relationship between the drained and undrained bulk modulus of a porous medium is often used to relate the dry bulk modulus to the saturated bulk modulus for elastic waves, because the compressibility of air is considered so high that the dry rock behaves in a drained fashion and the frequency of elastic waves is considered so high that the saturated rock behaves in an undrained fashion. The bulk modulus calculated from ultrasonic velocities, however, often does not match the Gassmann prediction. Mavko and Jizba examined how local flow effects and unequilibrated pore pressures can lead to greater stiffnesses. Their conceptual model consists of a distribution of porosities obtained from the strain-versus-confining-pressure behavior. Stiff pores that close at higher confining pressures are considered to remain undrained (unrelaxed) while soft pores drain even for high-frequency stress changes. If the pore shape distribution is bimodal, then the rock approximately satisfies the assumptions of a double-porosity, poroelastic material. Berryman and Wang [1995] established linear constitutive equations and identified four different time scales of ow behavior: (1) totally drained, (2) soft pores are drained but stiff pores are undrained, (3) soft and stiff pores are locally equilibrated, but undrained beyond the grain scale, and (4) both soft and stiff pores are undrained. The relative magnitudes of the four associated bulk moduli will be examined for all four moduli and illustrated for several sandstones.
Date: September 16, 1998
Creator: Berryman, J. G. & Wang, H. F.
Partner: UNT Libraries Government Documents Department

New perspectives on the fracture of Nicalon fibers

Description: Experimental studies have been conducted to examine the strength and fracture behavior of monofiliment Nicalon{sup 3} SiC fibers ranging in diameter from 8 to 22 {mu}m. The effects of varying fiber diameter, flaw location and flaw population on the tensile behavior of individual fibers were investigated using fractography. Results indicate that variations in fiber diameter influence the apparent fiber fracture toughness K{sub 1c}, with higher K{sub 1c} values observed for decreasing fiber diameters. Observations also suggest that the location of the critical flaw may play a role in the fracture of Nicalon fibers. In addition to surface flaws, three distinct internal flaw populations are seen to cause fracture in Nicalon fibers.
Date: November 1, 1997
Creator: Taylor, S.T.; Lowe, T.C. & Butt, D.P.
Partner: UNT Libraries Government Documents Department