Background-oriented schlieren with natural background for quantitative visualization of open-air explosions

Mizukaki, Toshiharu; Wakabayashi, Kunihiko; Matsumura, Tomoharu; Nakayama, Katsuyuki

doi:10.1007/s00193-013-0465-4

Cited by 26 publications

(18 citation statements)

References 11 publications

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“…Since the spread of breathing air may exceed this distance, BOS was used in further investigations to avoid these spatial restrictions. BOS as a relatively young visualization method (Meier 1999) is used in numerous fields, such as the visualization of open-air explosions (Mizukaki et al 2014), three-dimensional reconstruction of large-scale blade-tip vortices of a flying helicopter (Bauknecht et al 2015), and instantaneous three-dimensional density field reconstruction (Nicolas et al 2016).…”

Section: Introductionmentioning

confidence: 99%

The spread of breathing air from wind instruments and singers using schlieren techniques

Becher¹,

Gena²,

Alsaad³

et al. 2021

Preprint

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In this article, the spread of breathing air when playing wind instruments and singing was investigated and visualized using two methods: (1) schlieren imaging with a schlieren mirror and (2) background-oriented schlieren (BOS). These methods visualize airflow by visualizing density gradients in transparent media. The playing of professional woodwind and brass instrument players, as well as professional classical trained singers, were investigated to estimate the spread distances of the breathing air. For a better comparison and consistent measurement series, a single high and a single low note as well as an extract of a musical piece were investigated. Additionally, anemometry was used to determine the velocity of the spreading breathing air and the extent to which it was still quantifiable. The results presented in this article show there is no airflow escaping from the instruments, which is transported farther than 1.2 m into the room. However, differences in the various instruments have to be considered to assess properly the spread of the breathing air. The findings discussed below help to estimate the risk of cross-infection for wind instrument players and singers and to develop efficacious safety precautions, which is essential during critical health periods such as the current COVID-19 pandemic.

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Section: Introductionmentioning

confidence: 99%

The spread of breathing air from wind instruments and singers using schlieren techniques

Becher¹,

Gena²,

Alsaad³

et al. 2021

Preprint

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show abstract

“…Hence, the aforementioned research and other optical-based image tracking studies, e.g. [17] and [18], focus on the intermediate to far-field region where the shock front is freely expanding and has detached from the detonation product fireball. Alternative approaches use pressurised glass spheres [19] or detonation transmission tubing [20] in place of the explosive.…”

Section: Introductionmentioning

confidence: 99%

Reflected Near-field Blast Pressure Measurements Using High Speed Video

et al. 2020

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Background: The design and analysis of protective systems requires a detailed understanding of, and the ability to accurately predict, the distribution of pressure loads acting on an obstacle following an explosive detonation. In particular, there is a pressing need for accurate characterisation of blast loads in the region very close to a detonation, where even small improvised devices can produce serious structural or material damage. Objective: Accurate experimental measurement of these near-field blast events, using intrusive methods, is demanding owing to the high magnitudes (> 100 MPa) and short durations (< 1 ms) of loading. The objective of this article is to develop a non-intrusive method for measuring reflected blast pressure distributions using image analysis. Methods: This article presents results from high speed video analysis of nearfield spherical PE4 explosive blasts. The Canny edge detection algorithm is used to track the outer surface of the explosive fireball, with the results used to derive a velocity-radius relationship. Reflected pressure distributions are calculated using this velocity-radius relationship in conjunction with the Rankine-Hugoniot jump conditions. Results: The indirectly measured pressure distributions from high speed video are compared with directly measured pressure distributions and are shown to be in good qualitative agreement with respect to distribution of reflected pressures, and in good quantitative agreement with peak reflected pressures (within 10% of the maximum recorded value). Conclusions: The results indicate that it is possible to accurately measure blast loads in the order of 100s MPa using techniques which do not require sensitive recording equipment to be located close to the source of the explosion.

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“…Since its introduction, the BOS technique has attracted the attention of many scholars and is still continuously developed [21]. At present, the BOS technique is mainly used in the field of density measurements of a fluid field, fluid field visualization, temperature measurements, aero-optical wavefront measurements, and optical transfer function measurements [25,27,28]. The spot pattern in the digital image correlation method can be used as the background pattern in the BOS technique.…”

Section: Principle Of Background-oriented Schlierenmentioning

confidence: 99%

A Correction Method for Heat Wave Distortion in Digital Image Correlation Measurements Based on Background-Oriented Schlieren

Zeng

Zhang

et al. 2019

Applied Sciences

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Digital image correlation (DIC) is a kind of displacement and strain measurement technique. It can realize non-contact and full-field measurement and is widely used in the testing and research of mechanical properties of materials at high temperatures. However, many factors affect measurement accuracy. As the high temperature environment is complex, the impact of heat waves on DIC is the most significant factor. In order to correct the disturbance in DIC measurement caused by heat waves, this paper proposes a method based on the background-oriented schlieren (BOS) technique. The spot pattern on the surface of a specimen in digital image correlation can be used as the background in the background-oriented schlieren technique. The BOS technique can measure the distortion information of the images caused by heat flow field. The specimen images taken through the heat waves can be corrected using the distortion information. Besides, the characteristics of distortions due to heat waves are also studied in this paper. The experiment results verify that the proposed method can effectively eliminate heat wave disturbances in DIC measurements.

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Background-oriented schlieren with natural background for quantitative visualization of open-air explosions

Cited by 26 publications

References 11 publications

The spread of breathing air from wind instruments and singers using schlieren techniques

The spread of breathing air from wind instruments and singers using schlieren techniques

Reflected Near-field Blast Pressure Measurements Using High Speed Video

A Correction Method for Heat Wave Distortion in Digital Image Correlation Measurements Based on Background-Oriented Schlieren

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