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Overpressure

About: Overpressure is a research topic. Over the lifetime, 3236 publications have been published within this topic receiving 34648 citations.


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Proceedings ArticleDOI
05 May 2008
TL;DR: In this paper, an extensive database of low-to normal-intensity booms (overpressures of 0.08 lbf/sq ft to 2.20 lbf /sq ft) was collected for propagation code validation, and initial results and flight research techniques were presented.
Abstract: An extensive sonic boom propagation database with low- to normal-intensity booms (overpressures of 0.08 lbf/sq ft to 2.20 lbf/sq ft) was collected for propagation code validation, and initial results and flight research techniques are presented. Several arrays of microphones were used, including a 10 m tall tower to measure shock wave directionality and the effect of height above ground on acoustic level. A sailplane was employed to measure sonic booms above and within the atmospheric turbulent boundary layer, and the sailplane was positioned to intercept the shock waves between the supersonic airplane and the ground sensors. Sailplane and ground-level sonic boom recordings were used to generate atmospheric turbulence filter functions showing excellent agreement with ground measurements. The sonic boom prediction software PCBoom4 was employed as a preflight planning tool using preflight weather data. The measured data of shock wave directionality, arrival time, and overpressure gave excellent agreement with the PCBoom4-calculated results using the measured aircraft and atmospheric data as inputs. C-weighted acoustic levels generally decreased with increasing height above the ground. A-weighted and perceived levels usually were at a minimum for a height where the elevated microphone pressure rise time history was the straightest, which is a result of incident and ground-reflected shock waves interacting.

15 citations

Journal ArticleDOI
TL;DR: In this article, the authors used Digital Image Correlation and ultra-high speed photography to acquire full-field displacement measurements of panel deflections at frame rates of up to 1,000,000 frames per second and used them in the optimisation of a finite element model, outputting the parameters of an acoustic shock that produces representative displacements, velocities and accelerations.
Abstract: The effect of lightning attachment to structures and vehicles is a cause of major concern to a number of different industries, in particular the aerospace industry, where the consequences of such an event can be catastrophic In 1963, a Boeing 707 was brought down in Maryland killing 81 people on board, triggering the improvement of lightning protection standards However, commercial jets are still struck on average once every 10,000 hours of flight time and between 1963 and 1989 forty lightning related accidents were recorded within the USA alone The rapid increase in the use of composite materials in aircraft design and the consequent increase in complexity when determining the effects of a lightning strike, has led to new challenges in aircraft protection and the requirement for improved understanding and standardisation The attachment of lightning to a structure causes damage through three mechanisms Primarily a supersonic acoustic shock wave, caused by rapid heating of the arc channel during initial attachment, resulting in a large and rapid overpressure Secondly a magnetic force generated by the fields developed in the high current areas around the lightning attachment point Finally a mechanism specifically related to composite materials, where the rapid vaporisation of an expanded copper foil layer (designed to quickly transmit current across a structure, thus reducing its focus) trapped between the composite material and the protective paint layers causes an additional overpressure, which is exacerbated by additional paint layers acting to contain the explosion and direct it inwards The work described in this paper looks to develop a technique to measure these forces in order to better understand and assess their effects A novel methodology has been developed to allow the estimation of peak overpressure forces produced by the acoustic shock wave resulting from the attachment The methodology utilises Digital Image Correlation and ultra-high speed photography to acquire full-field displacement measurements of panel deflections at frame rates of up to 1,000,000 frames per second The experimental results are used in the optimisation of a finite element model, outputting the parameters of an acoustic shock that produces representative displacements, velocities and accelerations The method is currently being validated by performing a series of tests on aluminium panels subject to instrumented impact testing The next stage will be to use the technique developed to aid a program of investigation into the effects of artificial lightning strike events on aluminium and composite panels

15 citations

Journal ArticleDOI
TL;DR: In this article , the effect of ignition, initial pressure and temperature on the lower flammability limit (LFL) of hydrogen/air mixture are investigated experimentally and numerically.

15 citations

Journal ArticleDOI
TL;DR: In this article, an analysis of data obtained from explosion experiments carried out as part of the CEC (Commission of the European Communities) collaborative project MERGE (Modeling and Experimental Research into Gas Explosions).

15 citations

01 Jan 2013
TL;DR: In this paper, a study of up to 2.5 km (8000 ft) of gas-bearing shale has shed new light on the relationship between geochemistry and overpressure.
Abstract: A study of up to 2.5 km (8000 ft) of gas-bearing shale has shed new light on the relationship between geochemistry and overpressure. Our analysis of a few large geochemical data sets has also identified alternative ways to look at down-hole pressures and has revealed some limitations of currently available tools, such as Rock-Eval pyrolysis below a certain depth in Alberta and Quebec. The very thick Ordovician Shale of the St. Lawrence Lowlands in Quebec is gas-bearing and prospective. Whereas the prime target is the carbonate-rich Utica Shale, the overlying and thick Lorraine Shale was also studied. Recent Quebec geochemical data from the St. Lawrence Lowlands was analyzed together with hydraulic fracture and reservoir pressure data from the same wells. The first phase of the study focused exclusively on vertical wells and delivered new insights with respect to pressure domains and fracture gradients. Initial shut-in pressures (ISIPs) measured during hydraulic fracture jobs have been studied per well and per area in conjunction with geochemical data (percentage of methane, ethane, propane, wetness, and carbon isotopes). There is a remarkable correlation between wetness, isotope reversal, and ISIP in each well. Our analysis indicates that the traditional pressure gradient calculation could be challenged because some of the harder and easier rocks to fracture (to initiate breakdown, which depends on SHmin, SHmax, down-hole pressure, well bore orientation, and so on) have seemingly the same fracture gradients. An isotope reversal for both ethane and propane takes place at a depth where Rock-Eval data begin to become erratic because of low S2 peaks. That depth coincides with the ISIP trends per well intersecting the normal fracture gradient and is related to the limit between a naturally pressured domain and an overpressured domain located below it. Our study indicates that this overpressure/isotope reversal depth could be used to accurately calculate the reservoir pressure at any depth within the overpressure domain.

15 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023263
2022504
2021174
2020173
2019171
2018174