Showing papers on "Overpressure published in 1970"

An Experimental Study of Tectonic Overpressure in Franciscan Rocks

Abstract: Approximately 4 kb tectonic overpressure was required, according to one theory, for the formation of jadeite-aragonite-bearing rocks of the Franciscan. Strength of two common Franciscan rocks—massive graywacke, and thin-bedded shale and graywacke—was determined to see if this tectonic overpressure could have been generated under the conditions of metamorphism; that is, 4 kb confining pressure, 200 to 300° C, in the presence of aqueous pore fluid. The strength was found to depend markedly on both pore and total pressures. The required tectonic overpressure could only have been generated in massive graywacke, and only when pore pressure was less than hydrostatic. With even moderate amounts of interbedded shale, tectonic overpressure could not have exceeded 1 kb.

Shock Wave from a Four-Meter Spark

Abstract: The shock wave emitted by a 4‐m spark of energy 2×104 J has been measured at distances from spark midgap of between 0.34 and 16.5 m. Close to the spark, a single dominant shock wave is observed; farther from the spark, a number of significant shock waves (generally 3 or 4) are observed. For distances less than 2 m, both the shock overpressure and the duration of the overpressure are between a factor of 1.5 to 5 less than predicted by cylindrical shock‐wave theory. The discrepancies between the experimental data and cylindrical shock‐wave theory are partially explained by consideration of the spark channel tortuosity.

Device for sonic boom reduction and improving aircraft performance

Abstract: Method and means for improving the performance of, and particularly for reducing the sonic boom produced by a supersonic aircraft, comprising the production of a jet stream of approximately equal pressure but higher Mach number than the ambient supersonic flow, which steam is directed below the wing leading edge to intercept and interact with the wing shock wave. The interaction weakens the wing shock and decreases its propagation velocity, so that the wing shock, which normally reinforces the leading nose shock at the ground, will be shifted aftward spatially and in time in the boom signature, and will be delayed in its arrival with respect to the leading nose shock at any fixed position on the ground. By thus altering the signature, both the peak overpressure and the positive impulse of the boom may be substantially reduced without affecting the lift in support of the aircraft. Indeed, proper use of the stream will increase the lift on the aircraft, permitting some decrease in the angle of attack in maintaining level flight, which further weakens the wing shock to add to the altering of the boom signature. Also, the increase in lift, occurring largely on the aft part of the wing, results in reduction in drag, aftward shift of the center of pressure, and increase in the aerodynamic efficiency factor or lift-to-drag ratio, so that the jet stream can be used to improve various aspects of aircraft performance. Supersonic aircraft equipped with the anti-boom means, and a particular feasible means for producing the antiboom jet using existing technology are described, along with particular alternatives for the manner of incorporating the means on existing supersonic transports.

Electromagnetic propulsion device for use in the forward part of a moving body

Abstract: At least two parallel annular electrodes are disposed on the outside dielectric surface of the body starting from the forward edge thereof, perpendicularly to the direction of the symmetry axis of a magnetic field around the body. A propulsion electromagnetic force field is produced around the body such as to substantially decrease the overpressure in front of said moving body while accelerating the surrounding fluid backward and aside from said body, thereby to reduce the shock wave due to said overpressure.

On shock impedance

Abstract: The objective of the paper is to formulate a physically realistic definition of shock impedance. The definition obtained, expression (15), is consistent with the acoustic limit, with the Polachek & Seeger result for head-on shock incidence, and with the various reflexion limits. It seems to be applicable to all known regular and irregular refractions, with the possible exception of a refraction containing a Guderley patch. It is shown that one result of increasing impedance mismatch is to produce precursor and postcursor waves. It is thought the impedance mismatch caused by the jets of supersonic aircraft might be used to reduce the sonic boom overpressure.

Aerosol can with overpressure venting and entrapping means

Abstract: The present invention relates to an improvement in pressurized aerosol-dispensing containers, wherein a pressure-responsive overpressure relief means is strategically located as a structural part of the pressurized envelope and is combined with entrapping means thereon for restraining the violent escape of the dispensed product in the event that overpressure occurs.

The Response Of Civil Engineering StructuresTo Impulsive Loads

Abstract: The paper considers the accidental damage to buildings from explosive blast loading which has been back analysed to estimate the overpressure regime produced by the explosion. Such analyses in the past have led to the

Ground motion from sonic booms

Abstract: To ascertain the degree of hazard to structures from sonic-boom-induced ground vibrations, seismic measurements were made under NASA support during a series of sonic boom tests in 1967 and 1968. The maximum ground vibration velocity observed was 340 ju/sec at 90 Hz, corresponding to a sonic boom overpressure of 3.5 lb/ft. This is less than 1% of the structural damage threshold established experimentally by the U.S. Bureau of Mines and others, of 50,800 ju/sec. It is therefore very unlikely that any structural damage to slabs, foundations, wells, etc., can occur because of sonic booms. Incidental to the study, seismic precursor waves were observed which provide a possible basis for automatic warnings of approaching sonic booms, to reduce their startle effect.

Variation of Shock Overpressure with Distance in a Shock Tube Driven by an Exploding Gas Mixture

Abstract: Results are reported of calculations and measurements of the shock overpressure as a function of distance in an air shock tube driven by an exploding mixture of propane and oxygen.

Analytical Model for High Explosive Munitions Storage

Abstract: : Analytical models and subsequent computer codes have been developed for predicting peak overpressure, positive unit impulse, the distribution and impact velocity of bomb fragments, crater dimensions and ejecta thickness from the detonations of typical bomb stacks used by the Air Force. These models consider aboveground barricaded stacks with an equivalent net weight high- explosive range of 10 to 500 tons of TNT. The peak overpressure and impulse from a detonation are obtained by modifying the known results of a bare hemispherical charge to take into account the stack and barricade geometries and the interaction effect of bombs. Fragment dispersion patterns are predicted by combining experimental results for single bombs and using the trajectory equations for the motion of a steel fragment in air. By using basic principles and experimental data, crater and ejecta dimensions are predicted. Based on output from the computer codes, illustrative examples are given together with recommendations for future tests to obtain needed data. Programs for optimizing munition storage areas are also suggested.

Injection and dosing arrangements

Abstract: An arrangement for injecting a defined volume of a first fluid into a second streaming fluid is provided. The injection is carried out by separating two normally sealed tube sections through which the streaming fluid passes. The fluid to be injected is supplied to a chamber which surrounds the junction of the sections. An overpressure is obtained in the chamber, the overpressure generating an axial force which separates the sections and opens a passage through which the fluid is injected.

Blast Wave Yields for an Explosion

Abstract: : A blast wave overpressure-time history contains voluminous data which can be greatly simplified by converting them into equivalent yield. This calculation requires two independent parameters, usually chosen from measurements on peak overpressure, impulse, standoff distance, or travel time. Representative computations are described. Concurrence among the results of these for a particular explosion indicates a simple explosion situation and reliable data; divergence implies some effect such as focussed blast, or perhaps errors in measurement. All such information is useful in evaluation of blast wave data, and can contribute to our understanding of explosion phenomena.

Pressure equilibration around ejecta in a nuclear surface burst.

Abstract: : In order to simulate the equilibration of air blast overpressure around an ascent ejecta fragment in a nuclear surface burst, calculations were made of impulsive viscous flow of a polytropic gas into an L-shaped crack. (Author)

Effects of Air Blast on Urban Fires.

Abstract: : An experimental investigation was conducted of the effect of simulated nuclear blast waves on fires, simulating those that would be started in urban interiors due to thermal radiation that would have emanated from a 1 Mt-yield weapon assumed to be the source of the simulated blast. Blast waves in the range 1 to 5 psi nominal overpressure propagated through windows in a non-failing wall into full-scale test rooms furnished as typical living room, bedroom and office occupancies. The fire-blast interaction, in various combinations of occupancy and incident overpressure, and for non-failing walls having two different window areas, was documented by conventional and high-speed motion picture photography, and by post-test photography and recorded observations. (Author)