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The structure of a separating turbulent boundary layer. IV - Effects of periodic free-stream unsteadinessMeasurements were obtained of the sinusoidal unsteadiness of the free stream velocity during the separation of the turbulent boundary layer. Data were gathered by single wire and cross-wire, anemometry upstream of flow detachment, by laser Doppler velocimetry to detect the movement of the flow in small increments, and by a laser anemometer in the detached zone to measure turbulence and velocities. The study was restricted to a sinusoidal instability frequency of 0.61 and a ratio of oscillation amplitude to mean velocity of 0.3. Large amplitude and phase variations were found after the detachment, with unsteady effects producing hysteresis in the relationships between flow parameters. The detached shear layer decreased in thickness with increasing free-stream velocity and increases in the Reynolds shear stress. Deceleration of the free stream velocity caused thickening in the shear layer and upstream movement of the flow reversal location. The results are useful for studies of compressor blade and helicopter rotors in transition.
Document ID
19830043196
Document Type
Reprint (Version printed in journal)
Authors
Simpson, R. L. (Southern Methodist Univ. Dallas, TX, United States)
Shivaprasad, B. G. (Southern Methodist Univ. Dallas, TX, United States)
Chew, Y.-T. (Southern Methodist University Dallas, TX, United States)
Date Acquired
August 11, 2013
Publication Date
February 1, 1983
Publication Information
Publication: Journal of Fluid Mechanics
Volume: 127
Subject Category
FLUID MECHANICS AND HEAT TRANSFER
Funding Number(s)
CONTRACT_GRANT: DAAG29-76-G-0187
CONTRACT_GRANT: NSG-2354
Distribution Limits
Public
Copyright
Other