Validation of CFD Density Field Validation in Supersonic Axisymmetric Flows Using BOS and Differential Interferometry

Sourgen, F.; Haertig, J.; George, A.; Rey, Christian

doi:10.2514/6.2005-6036

Cited by 5 publications

(6 citation statements)

References 2 publications

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“…Therefore, its accuracy and sensitivity depend strongly on the characteristics of the BOS system. Sourgen et al [2,3] and Elsinga et al [4] studied the accuracy via comparison of experimental data derived using BOS, differential interferometry and computational fluid dynamics. The results showed that the accuracy of BOS is about 2% in most regions of the flow field.…”

Section: Principle Of Bos-wtmentioning

confidence: 99%

“…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].…”

mentioning

confidence: 99%

“…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 magnification factor [2]. Similar to traditional Schlieren, BOS is usually used for planar or axisymmetric flow-fields [2][3][4]6,7].…”

mentioning

confidence: 99%

“…For BOS, the spatial resolution depends on the integration window size, grid size, and magnification factor [2]. Similar to traditional Schlieren, BOS is usually used for planar or axisymmetric flow-fields [2][3][4]6,7]. For three-dimensional steady flows, a BOS system performs several measurements in various directions, and then reconstructs the results.…”

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confidence: 99%

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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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Section: Principle Of Bos-wtmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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

Tian

Zhao

et al. 2011

Chin. Sci. Bull.

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“…In 2004, Venkatakrishnan and Meier went into particulars the principle the BOS, and measured the density field of a cone cylinder model in supersonic flow with Ma=2.0 [8] . Sourgen et al [9] analyzed the precision, spatial resolution and application limitation of BOS, and evaluated the performance of BOS synthetically using examples in 2005. BOS and interferometry have different optical principles, but the density information yielded from both of them is integrated along the ray trajectory, so their ability to measure 3D density field is very limited.…”

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confidence: 99%

Study of density field measurement based on NPLS technique in supersonic flow

Tian

Zhao

et al. 2009

Sci. China Ser. G-Phys. Mech. Astron.

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Due to the influence of shock wave and turbulence, supersonic density field exhibits strongly inhomogeneous and unsteady characteristics. Applying traditional density field measurement techniques to supersonic flows yields three problems: low spatiotemporal resolution, limitation of measuring 3D density field, and low signal to noise ratio (SNR). A new method based on Nano-based Planar Laser Scattering (NPLS) technique is proposed in this paper to measure supersonic density field. This method measures planar transient density field in 3D supersonic flow by calibrating the relationship between density and concentration of tracer particles, which would display the density fluctuation due to the influence of shock waves and vortexes. The application of this new method to density field measurement of supersonic optical bow cap is introduced in this paper, and the results reveal shock wave, turbulent boundary layer in the flow with the spatial resolution of 93.2 μm/pixel. By analyzing the results at interval of 5 μs, temporal evolution of density field can be observed.

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Improved Flow Visualization Methods Based on the Background Oriented Schlieren Technique

純一

伸治²,

眞治³

2011

Trans.JSME, Ser.B

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This paper propose two new flow visualization methods based on the Background-Oriented Schlieren (BOS) technique for compressible flow. One is "Simplified background-oriented schlieren (S-BOS) ". This technique does not require a cross-correlation algorithm, which is typically used in BOS. The data processing is much simpler than that of the original BOS, since image displacement associated with density gradient is algebraically calculated from intensities of the images with the periodic background pattern. Moreover, it easily allows us to automate the data processing, because it is neither necessary to remove incorrect vectors nor to optimize parameters such as the interrogation window and search window. The other is referred to "Wavelet-based background-oriented schlieren (W-BOS)". This technique provides a schlieren image using continuous wavelet transformation for the periodic background pattern. By transforming the periodic intensity pattern into the phase, a schlieren image can be obtained easily. Since the optical setup in both techniques is simpler than that of a conventional schlieren imaging, they could be used in various situations including field tests. A wind tunnel test was conducted in a 1 m × 1 m supersonic wind tunnel. Their usefulness was demonstrated by comparing with the conventional schlieren images.

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Validation of CFD Density Field Validation in Supersonic Axisymmetric Flows Using BOS and Differential Interferometry

Cited by 5 publications

References 2 publications

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

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

Study of density field measurement based on NPLS technique in supersonic flow

Improved Flow Visualization Methods Based on the Background Oriented Schlieren Technique

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