The background oriented schlieren technique: sensitivity, accuracy, resolution and application to a three-dimensional density field

2007 ◽  
Vol 43 (2-3) ◽  
pp. 241-249 ◽  
Author(s):  
Erik Goldhahn ◽  
Jörg Seume
Keyword(s):  
Three Dimensional ◽  
Density Field ◽  
Schlieren Technique ◽  
Background Oriented Schlieren

scholarly journals Three-dimensional density measurements of a heated jet using laser-speckle tomographic background-oriented schlieren

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Shoaib Amjad ◽  
Julio Soria ◽  
Callum Atkinson
Keyword(s):  
Refractive Index ◽  
Turbulent Flows ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Density Field ◽  
Laser Speckle ◽  
Spatial Density ◽  
Reference Image ◽  
Mixing Processes ◽  
Background Oriented Schlieren

Three-dimensional density field measurement techniques can be used to understand the complex heat transfer and mixing processes that occur in turbulent flows. Tomographic background-oriented schlieren (BOS) is an optical technique that can be used to measure the instantaneous three-dimensional density field in turbulent flows. Light rays propagating through the flow are deflected from their ambient path due to variations in refractive index related to the spatial density gradients. In BOS, a camera is placed looking through the flow at a reference image, which captures path-integrated information on the refractive index gradients in the form of apparent image displacements Richard and Raffel (2001). The displacements recorded simultaneously from many cameras placed around the flow form the basis of a tomographic reconstruction of the three-dimensional refractive index gradients Goldhahn and Seume (2007), from which the density field is obtained through integration of the gradients and application of the Gladstone-Dale relation.

Application of the Quantitative Monochrome Calibrated Schlieren Technique in a Highly Loaded Turbine Cascade Test

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Zhihong Zhou ◽  
Haotian Wang ◽  
Huoxing Liu
Keyword(s):  
Shock Wave ◽  
Image Processing ◽  
Boundary Condition ◽  
Density Field ◽  
Dominant Factor ◽  
Turbine Cascade ◽  
Schlieren Technique ◽  
Computer Image Processing ◽  
Density Boundary ◽  
Highly Loaded

Abstract As the load of the turbine components of aircraft engines continuously increases, shock loss becomes the dominant factor of turbine stage loss and has become a hot topic. The Schlieren technique is one of the few effective experimental methods to observe and study shock wave and, thus, has been widely used. Nevertheless, limited by camera accuracy and computer image processing technology, quantitative schlieren analysis methods were difficult to achieve in engineering applications. Fortunately, several quantitative schlieren methods have been developed with the help of new digital technology. Applying the schlieren technique to the highly loaded turbine cascade test is of great significance to the study of shock wave in highly loaded turbine cascades. In this paper, the results of the quantitative density field and shock intensity and loss in the cascade are obtained by using a double-reflection-type monochrome schlieren device. The boundary condition of the density field is obtained by pressure test, and matlab software is used as image processing calculation tool. The quantitative results of this paper prove the feasibility of applying quantitative schlieren method to highly loaded turbine cascade tests. Also, the implemented image processing method and density boundary condition acquisition method are suitable and convenient for cascade flow and shock measurement tests.

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