One-way approximation for the simulation of weak shock wave propagation in atmospheric flows

Gallin, Louis-Jonardan; Rénier, Mathieu; Gaudard, Eric; Farges, Thomas; Marchiano, Régis; Coulouvrat, François

doi:10.1121/1.4869685

Cited by 28 publications

(8 citation statements)

References 30 publications

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“…The same type of variability was documented by Loucks et al [23] (their figures 15,16). As further illustrated on Fig.…”

Section: On the Shot-to-shot Variabilitysupporting

confidence: 61%

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Sensitivity of shot detection and localization to environmental propagation

Cheinet

Broglin

2015

Applied Acoustics

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“…The same type of variability was documented by Loucks et al [23] (their figures 15,16). As further illustrated on Fig.…”

Section: On the Shot-to-shot Variabilitysupporting

confidence: 61%

“…The understanding and prediction of these effects are an area of research (e.g. [16]). -Absorption and molecular relaxation by atmospheric gases cause an attenuation of high-frequency components of the signal with range.…”

Section: Shot Detection and Localizationmentioning

confidence: 99%

Sensitivity of shot detection and localization to environmental propagation

Cheinet

Broglin

2015

Applied Acoustics

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“…The meteorological conditions were not known with a sufficient time and space accuracy; thus, they induced a more important error than considering a straight line propagation. Advanced numerical simulations (Gallin et al, ) are too demanding for the present application.…”

Section: Methodsmentioning

confidence: 99%

Acoustical Measurement of Natural Lightning Flashes: Reconstructions and Statistical Analysis of Energy Spectra

et al. 2018

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Twenty-seven natural flashes of three thunderstorms which occurred during October 2012 in Southern France are acoustically reconstructed and analyzed in the [0.1 − 180]-Hz frequency bandwidth and the [0.3−20]-km distance range. A 50-m triangular array of four recalibrated microphones sampled at 500 Hz has been used for the recording. A novel method of separation of return strokes from intracloud discharges within the acoustical signal is detailed and systematically applied. It shows the possibility to separate nearby cloud-to-ground (CG) events or nearby and distant CGs of the same flash. The separation method yields a total of 36 return stroke signals and spectra, along with some intracloud signals. The combination of reconstruction, separation, and frequency analysis provides new insights on the origin of thunder infrasound, showing unambiguously that thunder infrasound originate dominantly from return strokes. Apart from the higher amplitude of CGs, no clear difference between intracloud and CG spectra is observed. No sharp frequency peaks can be put into evidence. The spectral variability with distance is highlighted, especially for the total acoustic energy and the center frequency and bandwidth. A link between acoustic energy and impulse charge moment change is also found, though only by a small number of data.The description of these two mechanisms explaining the infrasonic and audible acoustic content of thunder has been summarized by Few (1995). Regarding the audible content, the sudden core heating (25,000-30,000 K) just after the electric discharge produces a chain of strong shock waves along the lightning channel. The time dependence of pressure within the lightning channel was estimated by Orville (1968a) from the first measured time resolved optical spectra (Orville, 1968b), with peak overpressure exceeding 80 kPa. Based on a radiation thermodynamical model, Hill (1971) could simulate such values, with even higher shock amplitudes for shorter times (see his Figure 5). The different steps to switch from strong shock waves to weak shock waves and finally to acoustic waves are developed by Few (1969). Theory for self similar strong shock wave was proposed by Taylor (1950) for point sources and Lin (1954) for line sources and then numerically extended to transition and weak shock regimes by Brode (1955) for spherically symmetric shocks. The cylindrical symmetry was described by Plooster (1970). An empirical match between strong and weak shock theories has been applied to lightning by Jones et al. (1968) assuming a rectilinear channel. However, lightning channel tortuosity has been observed optically by Hill (1968), who proposed a mean value of 16 ∘ deflection of one segment to the next. Synthesizing these previous studies, Few et al. (1967) andFew (1969) assumed that the transition between strong and weak shocks takes place approximately in the same range of distances as the transition between cylindrical and spherical divergence. This distance is called relaxation radius. Indeed,

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“…Note however that ray theory is a high‐frequency approximation whose application at low frequencies is questionable. For the frequency bandwidth (1–100 Hz) and the propagation range (a few kilometers) over the ground here considered for thunder, numerical comparison between ray theory and simulations of nonlinear wave theory [ Gallin et al , , see their Figure 12] showed a good agreement for highest frequencies (50 or 100 Hz), while the typical features of ray theory such as formation of shadow zones or waveguides get largely blurred at lower frequencies (10 Hz). Moreover, ray tracing requires an accurate description of the meteorological profiles at the time when thunder is recorded by MPA.…”

Section: Acoustic Reconstruction Of Lightning Flashesmentioning

confidence: 99%

Statistical analysis of storm electrical discharges reconstituted from a lightning mapping system, a lightning location system, and an acoustic array

et al. 2016

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In the framework of the European Hydrological Cycle in the Mediterranean Experiment project, a field campaign devoted to the study of electrical activity during storms took place in the south of France in 2012. An acoustic station composed of four microphones and four microbarometers was deployed within the coverage of a Lightning Mapping Array network. On the 26 October 2012, a thunderstorm passed just over the acoustic station. Fifty‐six natural thunder events, due to cloud‐to‐ground and intracloud flashes, were recorded. This paper studies the acoustic reconstruction, in the low frequency range from 1 to 40 Hz, of the recorded flashes and their comparison with detections from electromagnetic networks. Concurrent detections from the European Cooperation for Lightning Detection lightning location system were also used. Some case studies show clearly that acoustic signal from thunder comes from the return stroke but also from the horizontal discharges which occur inside the clouds. The huge amount of observation data leads to a statistical analysis of lightning discharges acoustically recorded. Especially, the distributions of altitudes of reconstructed acoustic detections are explored in detail. The impact of the distance to the source on these distributions is established. The capacity of the acoustic method to describe precisely the lower part of nearby cloud‐to‐ground discharges, where the Lightning Mapping Array network is not effective, is also highlighted.

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One-way approximation for the simulation of weak shock wave propagation in atmospheric flows

Cited by 28 publications

References 30 publications

Sensitivity of shot detection and localization to environmental propagation

Sensitivity of shot detection and localization to environmental propagation

Acoustical Measurement of Natural Lightning Flashes: Reconstructions and Statistical Analysis of Energy Spectra

Statistical analysis of storm electrical discharges reconstituted from a lightning mapping system, a lightning location system, and an acoustic array

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