Alternative Title

Comparison of Visual and Conditioned Sampling Techniques


Two hot films and dye visualizations have been employed, simultaneously, in a turbulent boundary layer to explore the relations among visual observations and five kinds of detection methods using conditional sampling. The results show that all methods correlate positively with each other, but not with high enough values of correlation coefficients to indicate true correspondence between any two thus far studied. Moreover, none of the detection methods devised to date indicate a plateau in number of events as a function of trigger threshold.

The results also provide additional information on several other matters: (i) the relationship of outward motions from the wall (bursts) to inward motions (sweeps); (ii) further details on the time and space location of periods of high uv-product with respect to the visual models and to fluctuation hodograph quadrant, and (iii) some data bearing on the transfer of energy in the frequency domain during turbulence production (cascade processes). The present paper emphasizes the relations among the various detection methods and visual observations during intervals of high uv-product; other results are reported in more detail elsewhere.

Meeting Name

3rd Biennial Symposium on Turbulence in Liquids (1973: Sep., Rolla, MO)


Chemical and Biochemical Engineering


The work reported here was performed under the joint sponsorship of the National Science Foundation, Grant GK-27334, and the U.S. Air Force Office of Scientific Research, Mechanics Division Contract AF-F44620-C-0010.

Document Type

Article - Conference proceedings

Presentation Type

Invited Lecturer


Conditioned-Signal Analysis

Document Version

Final Version

File Type





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