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Boundary Layer Trips for Low Reynolds Number Wind Tunnel Tests

By Aldo Rona and H. Soueid

Abstract

This paper was presented at the 48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition, held at Orlando, Florida on 4-7 January 2010, and published in the 2010 Conference Proceedings. Copyright American Institute of Aeronautics and Astronautics. It is also available from http://www.aiaa.org/content.cfm?pageid=534&id=1818&luPubID=497 This paper appears in the LRA with the permission of the AIAA.The generation of a thick fully turbulent boundary layer is investigated in a lowspeed\ud wind tunnel at a nominal zero pressure gradient over the Reynolds number range\ud 0.145×106 · Rex · 0.58×106. The wind tunnel floor natural boundary layer is laminar with\ud thickness ± between 5.76 mm and 8.13 mm. Different tripping devices are tested to trigger\ud transition so to double the boundary layer thickness and provide a fully established turbulent\ud velocity profile. Using a trip wire significantly increases ± but leads to an unsatisfactory\ud velocity profiles. Using a sandpaper strip slightly increases ± but keeps the boundary layer\ud laminar. Using a strip of sharp-edged silicon granules doubles boundary layer thickness\ud that increases up to 20 mm and the mean velocity profiles are a good fit to the logarithmic\ud law of the wall over the outer region of the boundary layer. The spectral decay of turbulent\ud kinetic energy in this outer layer is exponential and close to −5/3, indicating turbulence\ud equilibrium. This work is of practical interest to wind tunnel practitioners for generating\ud equilibrium thick turbulent boundary layers at low Reynolds numbers

Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Year: 2010
OAI identifier: oai:lra.le.ac.uk:2381/7423

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