On the applicability of background oriented optical tomography for large scale aerodynamic investigations

Raffel, Markus; Richard, Hugues; Meier, G. E. A.

doi:10.1007/s003480050408

Cited by 159 publications

(61 citation statements)

References 15 publications

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“…It then calculates per-pixel deflection vectors using the optical flow. This class of methods [23,18] can acquire the shifts of pattern positions due to refractions but not directions. The 3D tomography technique by Atcheson et al [2] captures distorted wavelet noise patterns through the gas volume from multiple viewpoints.…”

Section: Related Workmentioning

confidence: 99%

Reconstructing Gas Flows Using Light-Path Approximation

2013

2013 IEEE Conference on Computer Vision and Pattern Recognition

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Section: Related Workmentioning

confidence: 99%

Reconstructing Gas Flows Using Light-Path Approximation

2013

2013 IEEE Conference on Computer Vision and Pattern Recognition

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“…Diagnostics of flows in supersonic and hypersonic facilities by BOS has been carried out in references [22][23][24][25][26], while in references [27][28][29] BOS has been used in the outdoors, with a large field of view. Several improvements of the technique are proposed, mainly in obtaining 3D measurements by tomographic imaging, [30][31][32], or by increasing the accuracy through colored backgrounds, [33].…”

Section: Principles Of Bosmentioning

confidence: 99%

Review of background oriented schlieren and development for ballistic range applications

Gojani

Kamishi

Obayashi

2013

EPJ Web of Conferences

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Abstract. Quantitative measurements of fluid flow can be achieved by flow visualization techniques, and this paper reviews and outlines background oriented schlieren, with emphasis on its performance: measurement sensitivity and uncertainty. Since the technique depends on cross-correlation, an assessment of image evaluation is also conducted. Background oriented schlieren is applied to two flows: shock reflection from a wedge in a shock tube, and natural cooling by convection. It is estimated that the technique can be applied to ballistic facilities.

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“…The setup of PIV mode is simpler than that of the Schlieren mode, and is more usable in full-scale flight tests, such as the flow-fields around helicopter airscrews [9], explosions [8] and gunshots flow-field [10]. The relatively low spatial resolution is the result of a lack of BOS of PIV mode.…”

Section: Bos-wtmentioning

confidence: 99%

“…For unsteady flows, however, several cameras and background images must be used to perform simultaneous measurements [5]. Additionally, the surrounding landscape can be used in BOS background images for full-scale flight tests [8][9][10][11].…”

mentioning

confidence: 99%

Aero-optical wavefront measurement technique based on BOS and its applications

Tian

Zhao

et al. 2011

Chin. Sci. Bull.

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A collimated light beam will be refracted if it propagates through a flow-field with index-of-refraction variations, and its wavefront will be distorted. If we measure the deflection angle of the light beam, the gradient of the wavefront can be obtained using the Malus law, and the wavefront aberration can be computed with a reconstruction algorithm. Two characteristics of background oriented schlieren (BOS) are conducive to wavefront aberration measurement: BOS can be used to measure the deflection angle of a light beam by measuring the displacement field between the reference image and the experiment image. Moreover, in a BOS system of Schlieren mode, only the ray perpendicular to the background image can be captured with a camera. This is helpful to measure wavefront aberrations that occur after a planar wavefront has passed through the flow-field. Based on these characteristics of BOS of Schlieren mode, a new wavefront measurement technique, which is called the BOS-based wavefront technique (BOS-WT), is proposed in this paper. It works by constructing the relationship between the displacement of the background image and the aero-optical wavefront gradient and uses the Southwell wavefront reconstruction algorithm. A BOS-WT system was assembled, and its temporal resolution was found to be 6 ns, and its temporal-correlation resolution reached 0.2 μs. A BOS-WT can measure the time-correlation transient wavefront quantitatively. It is simple and easy to operate. In this paper, we also present a study of the aero-optical performance of supersonic mixing layer based on our BOS-WT transient wavefronts at an interval of 5 μs. The results showed the wavefront was transient and distorted after it had passed through the mixing layer. Through the analysis of the data at the 5 μs interval, the temporal evolution of wavefront can be obtained. between them can be computed using cross correlation algorithms. Compared with traditional Schlieren, the facility of a BOS system is simpler. Also, BOS can measure the density gradients quantitatively in both the directions that are perpendicular to the light beam. Since its first demonstration, many researchers have been studying and estimating the properties of BOS, including its sensitivity, accuracy and spatial resolution. This has shown that the accuracy of BOS is very high [2][3][4]. However, there is some difficulty in studying the detached shock wave [3]. The sensitivity of a BOS system is primarily dependent on the arrangement of the BOS setup, the resolution of the CCD and the focal length of the CCD lens [5]. For BOS, the spatial resolution depends on the integration window size, grid size, and BOS, aero-optics, wavefront

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On the applicability of background oriented optical tomography for large scale aerodynamic investigations

Cited by 159 publications

References 15 publications

Reconstructing Gas Flows Using Light-Path Approximation

Reconstructing Gas Flows Using Light-Path Approximation

Review of background oriented schlieren and development for ballistic range applications

Aero-optical wavefront measurement technique based on BOS and its applications

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