Skin friction and laminar-sublayer thickness compressible turbulent boundary layers

Hebbar, Sheshagiri K and Paranjpe, PA (1969) Skin friction and laminar-sublayer thickness compressible turbulent boundary layers. Technical Report. National Aeronautical Laboratory, Bangalore, India.

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Abstract

Based on reference temperature technique for compressible flows and empirical laws of resistance for incompressible turbulent flows over smooth flat plates, simple, explicit and analytical expressions for the ratios of local skin- friction coefficient, average skin-friction coefficient and laminar-sublayer thickness in compressible turbulent boundary layers on smooth surfaces to the corresponding values in incompressible case for the same free stream13; conditions have been derived as functions of Mach number, Reynolds number, Prandtl number and wall-to-free-stream temperature ratio. The expressions for the ratios of skin friction coefficients compare very well with available experimental data including those at very high Reynolds number and those with heat transfer. The analysis brings out the appreciable effect of compressibility and heat transfer on skin-friction coefficient and laminar-sublayer thickness and therefore on maximum permissible roughness (based on the13; criterion of laminar-sublayer thickness) in compressible turbulent flows. High speed flows permit considerable increase in the permissible roughness whereas cooling of the surface decreases it. For the usual value of is entropic exponent equal to 1.4, the numerical results have been presented in the form of graphs to bring out quantitatively the appreciable effect of compressibility and heat transfer and for the convenience of users. An approximate estimate13; of the laminar-sublayer thickness based on local fluid properties has also been appended.

Item Type: Monograph (Technical Report)
Uncontrolled Keywords: Skin friction;Laminar-sublayer;Boundary layers;Empirical laws;13; Turbulent flows;Mach number;Recovery factor;Reynolds number
Subjects: AERONAUTICS > Aerodynamics
Depositing User: Users 90 not found.
Date Deposited: 02 Jan 2007
Last Modified: 24 May 2010 04:24
URI: http://nal-ir.nal.res.in/id/eprint/3725

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