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An Investigation of the Effect of a Highly Favorable Pressure Gradient on Boundary-Layer Transition as Caused by Various Types of Roughnesses on a 10-foot-Diameter Hemisphere at Subsonic SpeedsTests were made on a 10-foot-diameter hemispherical nose at Reynolds numbers up to 10 x 10(exp 6) and at a maximum Mach number of about 0.1 to determine the effects of a highly favorable pressure gradient on boundary-layer transition caused by roughness. Both two-dimensional and three-dimensional roughness particles were used, and the transition of the boundary layer was determined by hot-wire anemometers. The roughness Reynolds number for transition R(sub k,t) caused by three-dimensional particles such as Carborundum grains, spherical particles, and rimmed craters was found. The results show that for particles immersed in the boundary layer, R(sub k,t) is independent of the particle size or position on the hemispherical nose and depends mainly on the height-to-width ratio of the particle. The values of R(sub k,t) found on the hemispherical nose compare closely with those previously found on a flat plate and on airfoils with roughness. For two-dimensional roughness, the ratio of roughness height to boundary-layer displacement thickness necessary to cause transition was found to increase appreciably as the roughness was moved forward on the nose. Also included in the investigation were studies of the spread of turbulence behind a single particle of roughness and the effect of holes such as pressure orifices.
Document ID
19980231987
Acquisition Source
Headquarters
Document Type
Other - NASA Memorandum (MEMO)
Authors
Peterson, John B., Jr. (NASA Langley Research Center Hampton, VA United States)
Horton, Elmer A. (NASA Langley Research Center Hampton, VA United States)
Date Acquired
September 6, 2013
Publication Date
April 1, 1959
Subject Category
Fluid Mechanics And Heat Transfer
Report/Patent Number
NASA-MEMO-2-8-59L
L-172
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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