Engineering topics

Klebanoff, P. S.

Publications and source records attributed to Klebanoff, P. S..

2 records

NASA NTRS1980

Experimental investigation of drag on a compliant surface

The feasibility of reducing turbulent skin-friction drag by means of surface compliance was studied experimentally in a fully developed flat-plate turbulent boundary layer in air, using a membranous surface backed by a thin cavity containing a layer of polyurethane foam. Surface motion characteristics, boundary layer structure, and overall drag were measured over a range of freestream speeds from 7 to 30 m/sec, and a range of membrane tensions from 44 to 350 N/m. Low-amplitude long-wavelength motions predominate, and no significant change from the rigid surface skin-friction coefficients was observed.

Mcmichael, J. M.↗

NASA NTRS1972

Mechanism by which a two-dimensional roughness element induces boundary-layer transition.

An experimental investigation of the effect of two-dimensional roughness elements on boundary-layer transition is described. Primary emphasis is given to the nature of disturbances within the recovery zone. Detailed measurements of mean velocity distributions, of disturbance spectra, and intensity, growth, and decay of disturbances at discrete frequencies were made for a range of unit Reynolds numbers. The measurements demonstrate that the behavior can best be understood by considering wave-type disturbances, and that the basic mechanism by which a two-dimensional roughness element induces earlier transition to turbulent flow is by the destabilizing influence of the flow within the recovery zone.

Klebanoff, P. S.↗