Theory and application of quantitative, bidirectional color schlieren for density measurement in high speed flow

David W. Watt; Gerrit E. Elsinga; Bas W. van Oudheusden; Fulvio Scarano

doi:10.1117/12.510781

10 November 2003 Theory and application of quantitative, bidirectional color schlieren for density measurement in high speed flow

David W. Watt, Gerrit E. Elsinga, Bas W. van Oudheusden, Fulvio Scarano

Author Affiliations +

Proceedings Volume 5191, Optical Diagnostics for Fluids, Solids, and Combustion II; (2003) https://doi.org/10.1117/12.510781
Event: Optical Science and Technology, SPIE's 48th Annual Meeting, 2003, San Diego, California, United States

Abstract

This paper describes a quantitative schlieren technique called Calibrated Color Schlieren (CCS) that is capable of measuring the light deflection angle in both spatial directions simultaneously and hence is able to extract the projected density gradient of a two-dimensional flow. CCS makes use of a graded color filter in combination with a square source of size whose size may be varied to change the sensitivity. A calibration polynomial is used to obtain the deflection angle from color ratios at each pixel. The technique’s performance was assessed in terms of repeatability, sensitivity and accuracy using the Prandtl-Meyer expansion fan at the wedge-plate shoulder in a supersonic flow. From the measured deflection angles the density gradient and the density are computed. The density information agrees well with Prandtl-Meyer theory. The technique is also applied to a more complex wake flow, which required the use of a color correction based on a shadowgraph image.

Citation Download Citation

David W. Watt, Gerrit E. Elsinga, Bas W. van Oudheusden, and Fulvio Scarano "Theory and application of quantitative, bidirectional color schlieren for density measurement in high speed flow", Proc. SPIE 5191, Optical Diagnostics for Fluids, Solids, and Combustion II, (10 November 2003); https://doi.org/10.1117/12.510781

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