Investigation of effects of distributed surface roughness on a turbulent boundary layer over a body of revolution at a mach number of 2.01

John R. Sevier, Jr., K. R. Czarnecki
naca-tn-4183
Feb 1958


An investigation has been made of the effects of distributed surface roughness, consisting of lathe-tool marks, on the skin friction of a turbulent boundary layer over a body of revolution at a Mach number of 2.01. The investigation was made on three ogive-cylinders at zero angle of attack over a surface-roughness range from 23 to 480 microinches root mean square and for a Reynolds number range based on body length from 4 x 10-to-the-sixth to 30 x 10-to-the-sixth. The results indicate that the effects of distributed surface roughness on a turbulent boundary layer at a Mach number of 2.01 are generally similar to those found at a Mach number of 1.61 and at subsonic speeds. That is, for a given roughness height, some critical Reynolds number exists at which the skin friction begins to depart from the classical turbulent skin-friction law because of the form drag of the individual roughness particles. The results further indicate that (in the Reynolds number range of these tests) increasing the Mach number from 1.61 to 2.01 increases the allowable roughness for a turbulent boundary layer by about 40 percent. This increase is in good agreement with that predicted on the basis of a constant ratio of allowable roughness height to laminar-sublayer thickness or to a constant value of the Reynolds number based on allowable roughness height, shearing-stress velocity, and local conditions at the surface.

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