A new method of dynamic and static stall detection using infrared thermography

A new method of dynamic and static stall detection using infrared thermography A new method of detecting flow separation for static and pitching airfoils is described, with application to the generation of stall maps for helicopter rotors. An airfoil is heated using a lamp, and a high-speed infrared camera monitors the surface temperature. Subtracting consecutive images and performing a spatial standard deviation over a region of interest yields a single $$\sigma \hbox {DIT}$$ σ DIT value which is used to detect boundary layer separation on the airfoil. The data can be analysed to identify attached flow (low values of $$\sigma \hbox {DIT}$$ σ DIT ) and separated flow (high values of $$\sigma \hbox {DIT}$$ σ DIT ). Although appropriate filtering can significantly improve the signal-to-noise ratio, the method is robust regarding the exact method of analysis and the unfiltered data are sufficiently clear to be analysed without additional processing. For the test airfoil used, stall was measured up to a pitching frequency of 5 Hz, and signal-to-noise ratios indicate that it should be possible to measure stall for a pitching frequency of 20 Hz for a carbon-fibre surface with the thermal properties used. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Experiments in Fluids Springer Journals

A new method of dynamic and static stall detection using infrared thermography

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Publisher
Springer Berlin Heidelberg
Copyright
Copyright © 2016 by Springer-Verlag Berlin Heidelberg
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/s00348-016-2235-4
Publisher site
See Article on Publisher Site

Abstract

A new method of detecting flow separation for static and pitching airfoils is described, with application to the generation of stall maps for helicopter rotors. An airfoil is heated using a lamp, and a high-speed infrared camera monitors the surface temperature. Subtracting consecutive images and performing a spatial standard deviation over a region of interest yields a single $$\sigma \hbox {DIT}$$ σ DIT value which is used to detect boundary layer separation on the airfoil. The data can be analysed to identify attached flow (low values of $$\sigma \hbox {DIT}$$ σ DIT ) and separated flow (high values of $$\sigma \hbox {DIT}$$ σ DIT ). Although appropriate filtering can significantly improve the signal-to-noise ratio, the method is robust regarding the exact method of analysis and the unfiltered data are sufficiently clear to be analysed without additional processing. For the test airfoil used, stall was measured up to a pitching frequency of 5 Hz, and signal-to-noise ratios indicate that it should be possible to measure stall for a pitching frequency of 20 Hz for a carbon-fibre surface with the thermal properties used.

Journal

Experiments in FluidsSpringer Journals

Published: Sep 1, 2016

References

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