Computerized background-oriented schlieren

Computerized background-oriented schlieren A schlieren measurement technique based on computer evaluation of image variations due to refractive index variations in the propagation medium is presented; in what follows, this concept is referred to as the "background-oriented schlieren" (BOS) method. The differences between BOS and other optical techniques for refractive index measurement are the governing role of numerical methods, the extremely small amount of optical equipment, the high accuracy, the bidirectional sensitivity, the fast evaluation, and the missing field limitations. The principle of the method is the numerical comparison of a schlieren distorted and an undistorted image of a deliberate background. The method has become usable in practice owing to the immense progress in computing power and to newly developed fast-correlation algorithms. The extension of this method to space resolving techniques is possible. Some experimental studies show the applicability. Examples are a mixing turbulent jet, a supersonic jet, a shed vortex, and the sound wave of a gun shot. These few results underline the encouraging prospect for the future applicability of this technique. The BOS method offers not only the possibility of qualitative and quantitative schlieren investigations but also has the potential to determine density fields by integration of the measured gradient fields. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Experiments in Fluids Springer Journals

Computerized background-oriented schlieren

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Publisher
Springer-Verlag
Copyright
Copyright © 2002 by Springer-Verlag
Subject
Engineering; Engineering Fluid Dynamics; Fluid- and Aerodynamics; Engineering Thermodynamics, Heat and Mass Transfer
ISSN
0723-4864
eISSN
1432-1114
D.O.I.
10.1007/s00348-002-0450-7
Publisher site
See Article on Publisher Site

Abstract

A schlieren measurement technique based on computer evaluation of image variations due to refractive index variations in the propagation medium is presented; in what follows, this concept is referred to as the "background-oriented schlieren" (BOS) method. The differences between BOS and other optical techniques for refractive index measurement are the governing role of numerical methods, the extremely small amount of optical equipment, the high accuracy, the bidirectional sensitivity, the fast evaluation, and the missing field limitations. The principle of the method is the numerical comparison of a schlieren distorted and an undistorted image of a deliberate background. The method has become usable in practice owing to the immense progress in computing power and to newly developed fast-correlation algorithms. The extension of this method to space resolving techniques is possible. Some experimental studies show the applicability. Examples are a mixing turbulent jet, a supersonic jet, a shed vortex, and the sound wave of a gun shot. These few results underline the encouraging prospect for the future applicability of this technique. The BOS method offers not only the possibility of qualitative and quantitative schlieren investigations but also has the potential to determine density fields by integration of the measured gradient fields.

Journal

Experiments in FluidsSpringer Journals

Published: Jul 5, 2002

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