Boundary Layer Drag for Non-Smooth Surfaces
Abstract
The turbulent boundary-layer drag is studied for production-type or non-ideal aircraft surfaces. Stemming from the results of flight-test data for full-scale late-model aircraft; it has previously been concluded that there are no apparent Reynolds number effects on the zero-lift drag at flight speeds below the drag-rise Mach number. This independence of boundary layer drag on Reynolds number is made rational by reviewing the internal mechanism of the incompressible turbulent-boundary layer together with the basic empirical results; all as affected by surface roughness. It is concluded from fundamental concepts that the effects of roughness elements protruding from the laminar sub-layer will increase the vorticity and thus increase the momentum losses in the turbulent boundary layer. This additional momentum loss, or drag, due to roughness has been shown from the empirical evidence to offset the decreasing skin friction drag as the Reynolds number increases. Correspondingly, the above reasoning is extended to include the effects of compressibility in the turbulent boundary layer up to where the roughness elements themselves become locally affected and no longer are immersed in an incompressible field. As a consequence, for certain conditions, the compressible turbulent boundary layer drag for rough surfaces may also be considered independent of Reynolds number.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 24, 1953
- Accession Number
- ADA596196
Entities
People
- W. W. Gollos
Organizations
- RAND Corporation