Showing papers on "Effective porosity published in 1971"

Stability and Drag of Parachutes with Varying Effective Porosity

Abstract: : The tangent force, normal force, and moment coefficients versus the angle of attack of ten different types of parachutes were determined by means of wind tunnel measurements Models formed from sheet metal as well as made out of non-porous and porous cloth were used The nominal porosity of the cloth varied from 10 to 275 cu ft/sq ft min under a differential pressure of 1/2 inch of water This corresponds to a range of effective porosity from 0003 to 0096 The aerodynamic coefficients were related to the effective and nominal porosity characteristics expressed as derivatives with respect to the porosity term It was found that the static stability of all types of parachutes could be significantly improved through higher porosity, although this reduces slightly the air resistance for the parachute

Method for estimating effective porosity in a rubble chimney formed by an underground nuclear explosion

Abstract: Explosion of a nuclear device underground at the Nevada Test Site produced a rubble chimney which was completely dewatered at the time of its formation and required a period of about 5 yr for infill to the pre-explosion water level. Numerous pumping tests conducted during the period of infill of the chimney disclosed that pumping often caused an interruption in the rise of water level in the chimney. A method was devised for estimating the effective porosity of the chimney in selected zones by comparing the volume of water removed during a pumping test with the observed interruption in water-level rise resulting from infill. The porosity of the rubble chimney, determined by this method is between 1.5 and 7.9%.

Genetic Classification of Porosity Formation and Destruction in Carbonate Rocks: ABSTRACT

Abstract: For a proper evaluation of the reservoir potentialities of carbonate rocks the exact causes of porosity formation and destruction need to be known. Such a genetic approach to a classification has to be practical enough to be applicable at the well site, yet sophisticated enough to allow meaningful interpretations. All old attempts at classification of porosity have been either descriptive or insufficiently accurate. For example, the term "leaching" is meaningless, unless it is specified if it pertains to subaerial leaching, or leaching accompanying recrystallization, or leaching resulting from dolomitization. An attempt is made herein to propose a genetic classification which has been tested in its applicability, both at the well site and in the laboratory. There are basically 2 types of porosity--primary and secondary. Primary porosity developments were formed at time of deposition prior to diagenetic alterations of the sediment. Secondary porosity formations are introduced after deposition by early or late or even post-diagenetic activity. Primary porosity may be subdivided into intergrain and intragrain porosity. Secondary porosity formation may represent the following types: (1) subaerial leaching of the grains (moldic porosity) or the carbonate mud matrix; (2) recrystallization porosity, based primarily on (a) leaching accompanying the recrystallization process, (b) rearrangement of the crystal fabric (interstitial porosity), and (c) preservation of primary porosity by fast diagenetic hardening; (3) dolomitization porosity, based primarily on (a) leaching resulting from the dolomitization process, (b) volume reduction caused by a slight density difference between calcite and dolomite, (c) preservation of the primary porosity by fast diagenetic hardening, and (d) interstitial porosity created by dolomitization and subsequent recrystallization; (4) fracture porosity, either by itself or furthe enlarged by subsequent leaching. Partial or complete porosity destructions in carbonates result primarily from (a) fibrous calcite wall linings, (b) sparry calcite precipitation, (c) sparry dolomite precipitation, (d) anhydrite and gypsum infills, (e) infilling by other evaporites, (f) infill by clay, silt, or sand, (g) infill by carbonate mud, (h) infill by isolated dolomite rhombohedra, and (i) collapse of the former depositional fabric. End_of_Article - Last_Page 154------------

Causes of the occurrence of an “effective” porosity in granular media

Abstract: The cause of the difference between the total ɛ (geometric) and “effective” ɛef (hydrodynamic) porosity of granular media is established