Experiments have been performed to determine the fundamental nature of boundary layer separation produced by an adverse pressure gradient. Measurements upstream and downstream of the separation zone have been made utilizing laser and hot-film anemometry techniques.

A completely mobile backscattering laser anemometer was developed. This alone is a significant development because of the relatively long focal lengths required for measurements in a 36" wide wind tunnel. Signal processing was achieved by a digital signal sampling and storage system. Both mean and fluctuating velocities in both the unseparated and separated flow regions were measured. Experimental results are in fairly good agreement with hot-film measurements, with some recent improvements in data acquisition being noted.

Flush-wall hot-film sensors were used to determine wall shear stresses and fluctuations, both upstream and downstream of separation. These data indicate that the law of the wall apparently is valid up to the location of intermittent separation or the location of intermittent backflow next to the wall. Visual observations indicate that the location of intermittent separation is in agreement with Sandborn's criterion. The outer region flow downstream of the beginning of separation is characterized by a similarity mixing-layer velocity profile.

Meeting Name

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


Chemical and Biochemical Engineering


This work was sponsored by the U.S. Army Research Office - Durham under Grant DA-ARO-D-31- 124-72-G31. Initial development of the laser anemometer system was sponsored under NASA Grant NGL 44-007-006.

Document Type

Article - Conference proceedings

Presentation Type

Contributed Paper


Laser-Doppler Velocimetry

Document Version

Final Version

File Type





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