Background oriented schlieren for flow visualisation in hypersonic impulse facilities

Ramanah, Dwishen; Raghunath, Sreekanth; Mee, D. J.; Rösgen, Thomas; Jacobs, Peter A.

doi:10.1007/s00193-007-0097-7

Cited by 31 publications

(12 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Good agreement was found for 80% of the extracted horizontal displacement profile for value of freestream static density of ρ ∞ ≅ 1.7x10 −3 kg/𝑚 3 . A further study by Rammanah et al [17] studied a sharp A c c e p t e d M a n u s c r i p t 3 20 ο circular cone and a re-entry body at Mach 4 in the Drummond reflected shock tunnel, and processed the results using a PIV algorithm. The static density value for these tests was ρ ∞ ≅ 0.13 kg/𝑚 3 .…”

Section: Introductionmentioning

confidence: 99%

An experimental sensitivity comparison of the schlieren and background-oriented schlieren techniques applied to hypersonic flow

Fisher

Quinn

Smith

2019

Meas. Sci. Technol.

View full text Add to dashboard Cite

show abstract

Section: Introductionmentioning

confidence: 99%

An experimental sensitivity comparison of the schlieren and background-oriented schlieren techniques applied to hypersonic flow

Fisher

Quinn

Smith

2019

Meas. Sci. Technol.

View full text Add to dashboard Cite

show abstract

“…The density field chosen for the error analysis is a Gaussian density field, described by Equation (10),…”

Section: Analysis With Synthetic Imagesmentioning

confidence: 99%

Uncertainty quantification in density estimation from background-oriented Schlieren measurements

Rajendran¹,

Zhang

Bhattacharya

et al. 2020

Meas. Sci. Technol.

View full text Add to dashboard Cite

We present an uncertainty quantification methodology for density estimation from Background Oriented Schlieren (BOS) measurements, in order to provide local, instantaneous, a-posteriori uncertainty bounds on each density measurement in the field of view. Displacement uncertainty quantification algorithms from cross-correlation based Particle Image Velocimetry (PIV) are used to estimate the uncertainty in the dot pattern displacements obtained from cross-correlation for BOS and assess their feasibility. In order to propagate the displacement uncertainty through the density integration procedure, we also develop a novel methodology via the Poisson solver using sparse linear operators. Testing the method using synthetic images of a Gaussian density field showed agreement between the propagated density uncertainties and the true uncertainty. Subsequently the methodology is experimentally demonstrated for supersonic flow over a wedge, showing that regions with sharp changes in density lead to an increase in density uncertainty throughout the field of view, even in regions without these sharp changes. The uncertainty propagation is influenced by the density integration scheme, and for the Poisson solver the density uncertainty increases monotonically on moving away from the regions where the Dirichlet boundary conditions are specified.

show abstract

“…The best results are, thus, usually generated usi random dot background since it has high contrast and unique features which are ideal for im correlation algorithms to determine pixel shift. [5] The BOS method has been successfully employed as a quantitative measurement technique different applications, ranging from under-expanded axisymmetric jets [6] , multi-jet flows [ hypersonic shock waves [8] , supersonic separated flow [9] , and shock waves of a rifle disch and explosions [5] , to name a few. The current study aims to make use of the BOS techniqu look at the flow in an under-expanded rectangular jet and understand its developm downstream of the nozzle exit.…”

Section: Techniquementioning

confidence: 99%

“…The BOS method has been successfully employed as a quantitative measurement technique for different applications, ranging from under-expanded axisymmetric jets (6) , multi-jet flows (6,7) , hypersonic shock waves (8) , supersonic separated flow (9) , and shock waves of a rifle discharge and explosions (5) , to name a few. The current study aims to make use of the BOS technique to look at the flow in an under-expanded rectangular jet and understand its development downstream of the nozzle exit.…”

Section: Introductionmentioning

confidence: 99%

Density measurements for rectangular free jets using background-oriented schlieren

Tipnis

Finnis

Knowles

et al. 2013

Aeronaut. j. (1968)

View full text Add to dashboard Cite

An experimental study incorporating the use of the Background-Oriented Schlieren (BOS) technique was performed to measure the density field of a rectangular supersonic jet. This technique is easier to set up than conventional schlieren since the optical alignment involving the various mirrors, lenses and knife-edge is replaced by a background pattern and a single digital camera. The acquired images which contain information of density gradients in the flow are solved as a Poisson equation and further processed using deconvolution and tomographic algorithms to generate a 3D domain which contains information about the actual density. 2D slices can then be extracted to quantitatively visualise the density along any required planes. The results from supersonic axisymmetric jets are used for validation of the code; these show excellent agreement with pre-validated CFD data. The results for a rectangular supersonic jet are then obtained. These show good agreement with the CFD data, in terms of shock-cell spacing and overall structure of the jet. The technique has proved useful for investigating axis-switching, a phenomenon generally associated with non-axisymmetric jets.

show abstract

Background oriented schlieren for flow visualisation in hypersonic impulse facilities

Cited by 31 publications

References 11 publications

An experimental sensitivity comparison of the schlieren and background-oriented schlieren techniques applied to hypersonic flow

An experimental sensitivity comparison of the schlieren and background-oriented schlieren techniques applied to hypersonic flow

Uncertainty quantification in density estimation from background-oriented Schlieren measurements

Density measurements for rectangular free jets using background-oriented schlieren

Contact Info

Product

Resources

About