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Use of a pseudo-turbulent signal to calibrate an intermittency measuring circuit

Published online by Cambridge University Press:  29 March 2006

R. A. Antonia  and
J. D. Atkinson
R. A. Antonia
Affiliation:
Department of Mechanical Engineering, University of Sydney
J. D. Atkinson
Affiliation:
Department of Mechanical Engineering, University of Sydney
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Abstract

Measurements of the intermittency factor γ and in particular the crossing frequency fγ of the turbulent/non-turbulent interface in the outer regions of various turbulent shear flows depend strongly on the settings of the intermittency meter used. Two methods of calibrating an intermittency meter of conventional design are described. In the first, turbulent and non-turbulent signals are simulated and switched at random times using an analog computer. Particular attention is given to the spectra of the switching and turbulent signals but the non-turbulent signal is assumed to have the same spectrum as the turbulent signal. In the second method, the same switching process is applied to two real signals, obtained in the fully turbulent and irretational flow regions associated with a turbulent jet with a co-flowing external air stream. A rather simple calibration procedure derived using the results of both methods is applied to the measurements of γ and fγ in the same jet. It is suggested that the simulation process adopted here could be useful in inferring properties of intermittent turbulent flows.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 64 , Issue 4 , 24 July 1974 , pp. 679 - 699
Copyright
© 1974 Cambridge University Press

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