Mach stem formation in outdoor measurements of acoustic shocks

Leete, Kevin M.; Gee, Kent L.; Neilsen, Tracianne B.; Truscott, Tadd

doi:10.1121/1.4937745

Cited by 7 publications

(5 citation statements)

References 14 publications

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“…In this study, ETN blast wave parameters were compared with those of TNT and PETN, the peak overpressure was compared with standard curves of TNT (Baker, MITI87, and NRIPS09), and the TNT equivalent for each explosive was obtained. The effect of the reflected wave on the peak overpressure was identified; therefore, the waveforms and the Mach stem position were evaluated carefully . Figure shows that the height of the triple point was still below 0.6 m, where the pressure sensor was placed; therefore, the incident and reflected waves were separately recorded by the sensor at 3 m (Figure ).…”

Section: Discussionmentioning

confidence: 99%

“…and Leete et al. by using software (Photoshop Elements 10, Adobe). The differences between two adjacent frames were subtracted, and the gamma values and white balances were adjusted.…”

Section: Methodsmentioning

confidence: 99%

“…To help visualizet he shock front, ac hecked cloth was placed behind thee xplosion site. Camera images were edited to clarify the shock front according to Kudo et al and Leete et al [19,20] by using software (Photoshop Elements 10, Adobe). The differences betweent wo adjacent framesw ere subtracted, and the gamma values and white balances were adjusted.T he distance in the images was calculated by software (Pixel Runner,T ellusImage, Co.,L td.…”

Section: Visualization Of Shock Front By Using High-speed Camera Imagesmentioning

confidence: 99%

See 2 more Smart Citations

Blast Waves and Fragment Velocities of Erythritol Tetranitrate

Tagawa

Hiyoshi

Takeuchi

et al. 2016

Propellants Explo Pyrotec

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Erythritol tetranitrate (ETN) is a highly sensitive nitrate ester that has a similar molecular structure to nitroglycerine and penta‐erythritol tetranitrate (PETN). In this study, experiments detonating 175 g of ETN were repeated three times to measure blast waves 0.6 m above the ground. TNT and PETN were also tested under the same conditions for comparison. The average peak overpressure of ETN was about 30 kPa at 3 m from the explosion center (5.4 m kg−1/3 scaled distance), which was much higher than that of TNT (about 22 kPa) and similar to PETN. The effects of the reflected wave from the ground appeared at greater distances of 5 and 7 m (8.9 and 12.5 m kg−1/3, respectively), as verified by the waveforms and high‐speed camera images. Previous TNT data for peak overpressure vs. scaled distance were used to calculate the TNT equivalents for the experimental data, which revealed that ETN had a similar value to PETN. The fragments velocities of steel cylinders were measured, and that of ETN (1040 m s−1) was higher than that of TNT (957 m s−1) and lower than that of PETN (1260 m s−1). The Gurney constant for each explosive was obtained by using the initial fragment velocities.

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Section: Discussionmentioning

confidence: 99%

“…and Leete et al. by using software (Photoshop Elements 10, Adobe). The differences between two adjacent frames were subtracted, and the gamma values and white balances were adjusted.…”

Section: Methodsmentioning

confidence: 99%

Section: Visualization Of Shock Front By Using High-speed Camera Imagesmentioning

confidence: 99%

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Blast Waves and Fragment Velocities of Erythritol Tetranitrate

Tagawa

Hiyoshi

Takeuchi

et al. 2016

Propellants Explo Pyrotec

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“…Recent studies reporting experiments of weak shock reflection but at a larger scale than the present experiment showed a good agreement with a cubic law. 18 Although in our previous study with the same source a linear trajectory was reported, 13 that study was done for a small range of propagation distances r from 7 up to 13 cm. In the present study, the length of the Mach stem is analyzed from the three sets of data and at greater distances: with the Schlieren technique in the range from 10 up to 33 cm; with the interferometer in the range from 10 up to 37 cm, and with simulations up to 70 cm.…”

Section: Evolution Of the Mach Stemmentioning

confidence: 95%

“…In previous studies on shock wave reflections, optical methods were mainly used only for visualizing reflection patterns to determine the type of reflection. [15][16][17][18] Irregular reflection patterns and Mach stem formation can even be observed in one hundred-years-old photographs of pressure waves propagating in small room models. 19 However, in most cases, optical methods only provide a visualization of the location of shocks and do not provide a quantitative measure of pressure waveforms.…”

Section: Introductionmentioning

confidence: 99%

Irregular reflection of spark-generated shock pulses from a rigid surface: Mach-Zehnder interferometry measurements in air

Karzova

Lechat

Ollivier

et al. 2019

The Journal of the Acoustical Society of America

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The irregular reflection of weak acoustic shock waves, known as the von Neumann reflection, has been observed experimentally and numerically for spherically diverging waves generated by an electric spark source. Two optical measurement methods are used: a Mach-Zehnder interferometer for measuring pressure waveforms and a Schlieren system for visualizing shock fronts. Pressure waveforms are reconstructed from the light phase difference measured by the interferometer using the inverse Abel transform. In numerical simulations, the axisymmetric Euler equations are solved using finite-difference time-domain methods and the spark source is modeled as an instantaneous energy injection with a Gaussian shape. Waveforms and reflection patterns obtained from the simulations are in good agreement with those measured by the interferometer and the Schlieren methods. The Mach stem formation is observed close to the surface for incident pressures within the range of 800 to 4000 Pa. Similarly, as for strong shocks generated by blasts, it is found that for spherical weak shocks the Mach stem length increases with distance following a parabolic law. This study confirms the occurrence of irregular reflections at acoustic pressure levels and demonstrates the benefits of the Mach-Zehnder interferometer method when microphone measurements cannot be applied.

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