Quantitative Schlieren Measurement of Explosively‐Driven Shock Wave Density, Temperature, and Pressure Profiles

Tobin, Jesse D.; Hargather, Michael

doi:10.1002/prep.201600097

Cited by 19 publications

(4 citation statements)

References 31 publications

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“…Further quantification to temperature, pressure, or concentration measurements depends on a detailed knowledge of the gas species present as well as other flow properties. If only a single gas is involved, a simple state equation is used to determine temper ature from density if the pressure is known, or vice versa [35,98]. Evaluating gas mixtures this way requires accounting for variations in refractive index among the gases involved.…”

Section: Quantitative Analysis Of Schlieren Imagesmentioning

confidence: 99%

A review of recent developments in schlieren and shadowgraph techniques

Settles¹,

Hargather

2017

Meas. Sci. Technol.

328

154

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Schlieren and shadowgraph techniques are used around the world for imaging and measuring phenomena in transparent media. These optical methods originated long ago in parallel with telescopes and microscopes, and although it might seem that little new could be expected of them on the timescale of 15 years, in fact several important things have happened that are reviewed here. The digital revolution has had a transformative effect, replacing clumsy photographic film methods with excellent-though expensive-high-speed video cameras, making digital correlation and processing of shadow and schlieren images routine, and providing an entirely-new synthetic schlieren technique that has attracted a lot of attention: background-oriented schlieren or BOS. Several aspects of modern schlieren and shadowgraphy depend upon laptop-scale computer processing of images using an imagecapable language such as MATLAB ™. BOS, shock-wave tracking, schlieren velocimetry, synthetic streak-schlieren, and straightforward quantitative density measurements in 2D flows are all recent developments empowered by this digital and computational capability.

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Section: Quantitative Analysis Of Schlieren Imagesmentioning

confidence: 99%

A review of recent developments in schlieren and shadowgraph techniques

Settles¹,

Hargather

2017

Meas. Sci. Technol.

328

154

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“…100 gram spheres, cylinders, and cubes were handpacked into 3D printed molds to an average density of 1.5 g/cm 3 from rubberized Datasheet explosive, shown on a one-inch grid in Figure 5. The datasheet is a flexible sheet explosive consisting of 68 % PETN, 28 % acetyl tributyl citrate, and 8 % nitrocellulose [29]. The charges were placed on a 0.5 meter cardboard tube and initiated by an Austin Powder Rockstar electric blasting cap inserted 1.3 centimeters into the base of the charge.…”

Section: Methodsmentioning

confidence: 99%

Blast Wave Shaping by Altering Cross‐Sectional Shape

Williams

Langenderfer

Olbricht

et al. 2021

Propellants Explo Pyrotec

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Standoff distances for people and equipment are determined using a scaled distance calculation that assumes a uniform distribution of explosive energy, which only occurs with center-initiated spherical charges in free air without ground effects. There is a significant amount of data available for spheres and cylinders in air and hemispheres on the ground, but little has been published for other geometries. Published studies of spherical, cylindrical, and planar charges demonstrate that there is a focus on the blast wave resulting from charge geometry. From these studies, it appears that the highest overpressure occurs in the orientation of the largest presented surface area. This paper presents experimental pressure data recorded from the detonation of spherical, cylindrical, and cubic charges at two scaled distances. The non-spherical charges were in-strumented normal to two adjacent sides and the interjacent edge. The pressure normal to the sides of the cubic and cylindrical charges was up to 1.5 times that of the spherical charge in the near field, but lower in the far-field indicating that a simple multiplication factor will not accurately predict the overpressure over distance for complex charges from spherical data. The sides of the cubic charge produced a near field overpressure relative to its surface area consistent with those observed from the side and end of the cylindrical charge. In the far-field, the pressure from the sides of the charge was less than that of the sphere indicating that there is a lateral movement of energy behind the shock front causing a reversal of peak pressure in the measured orientations.

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“…As the temperature plays an important role in this process, a direct measurement of the gas temperature profiles is of great help in understanding the mechanism of the transition process. To achieve this goal, the quantitative Schlieren techniques [74] are good choices.…”

Section: Schlieren Observations For Long Sparksmentioning

confidence: 99%

Schlieren techniques for observations of long positive sparks: Review and application

Wang

Zhao

et al. 2022

High Voltage

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Understanding the mechanism of positive leader discharge is important in lightning protection engineering and the external insulation design in high voltage power transmission systems. During the propagation of a positive leader, some processes without light-emitting, for example, the insulation recovery process after the breakdown, cannot be observed by optical photography techniques. With the combination of the digital high-speed imaging system, the conventional Schlieren techniques offer new vistas in the long air gap discharge observation. The important features of high spatial resolution, high sensitivity, and easy arrangement make Schlieren techniques powerful and effective tools for characterising the discharge processes without light-emitting. This work presents a brief review of current Schlieren techniques and discusses the design of the Schlieren optics system for long spark observations. Several interesting phenomena discovered at different phases of long sparks with high-speed Schlieren techniques are also presented.

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Quantitative Schlieren Measurement of Explosively‐Driven Shock Wave Density, Temperature, and Pressure Profiles

Cited by 19 publications

References 31 publications

A review of recent developments in schlieren and shadowgraph techniques

A review of recent developments in schlieren and shadowgraph techniques

Blast Wave Shaping by Altering Cross‐Sectional Shape

Schlieren techniques for observations of long positive sparks: Review and application

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