Journal of Fluid Mechanics

Comparison of conditional sampling and averaging techniques in a turbulent boundary layer

C. S.  Subramanian a1, S.  Rajagopalan a1, R. A.  Antonia a1 and A. J.  Chambers a1
a1 Department of Mechanical Engineering, University of Newcastle, N.S.W. 2308, Australia

Article author query
subramanian cs   [Google Scholar] 
rajagopalan s   [Google Scholar] 
antonia ra   [Google Scholar] 
chambers aj   [Google Scholar] 


Visual examination of simultaneous temperature traces from a rake of cold wires placed across a turbulent boundary layer had enabled the identification of coherent temperature fronts. An X-wirelcold-wire arrangement was used simultaneously with the rake to provide measurements of the velocity fluctuations u (longitudinal) and v (normal) and the temperature fluctuation θ. Conditional averages of u, v, θ and products uv, uθ, vθ were obtained by application of conditional techniques based on the detection of the temperature fronts using information obtained at only one point in space. These averages, obtained at various positions across the layer, have been compared with those obtained when the rake was used to detect the fronts. The comparison has indicated that none of the one-point detection techniques is in good quantitative agreement with the rake detection technique, the largest correspondence between the rake technique and any ofthe other one-point techniques being only 51 yo. With the exception of the hole technique used in conjunction with the quadrant decomposition analysis, conditional averages obtained from one-point techniques are in reasonable qualitative agreement with those deduced using the rake.

(Published Online April 20 2006)
(Received January 28 1981)
(Revised January 26 1982)