Accession Number : AD0262486

Title :   THE EFFECT ON PROFILE DRAG OF RANDOMLY DISTRIBUTED, LOW-INTENSITY ROUGHNESS

Corporate Author : ADVISORY GROUP FOR AERONAUTICAL RESEARCH AND DEVELOPMENT PARIS (FRANCE)

Personal Author(s) : COLEMAN, W.S.

Report Date : APR 1960

Pagination or Media Count : 22

Abstract : The effect of randomly distributed roughness on the behaviour of the boundary layer is discussed in terms of the turbulent spots generated by the excrescences. Functions defining the intermittency factor for turbulence at any cross-section of the boundary layer are obtained, firstly, from the kinematical properties of spots, and secondly, in an Appendix, from the transition theory of Emmons (The Laminar-Turbulent Transition in a Boundary Layer. J. Aeronaut. Sci. 18:490, 1951, part 1). The two approaches are found to lead to substantially the same result. In the light of this analysis, the influence of the roughness on wing profile drag is considered. It is shown that an appreciable increase of drag may be expected to develop when the mean lateral spacing of the critical excrescences falls below about 0.5 of the chord. (Author)

Descriptors :   *BOUNDARY LAYER, *BOUNDARY LAYER CONTROL, *DRAG, *HYPERSONIC FLOW, *LOW DRAG AIRFOILS, *STABILITY, *TURBULENT BOUNDARY LAYER, AIRFOILS, COMPRESSIBLE FLOW, MODEL TESTS, STATISTICAL DISTRIBUTIONS, SUPERSONIC FLOW, SURFACE PROPERTIES, THEORY, TURBULENCE, WIND TUNNELS.

Distribution Statement : APPROVED FOR PUBLIC RELEASE