Uniform Roughness Studies
Abstract
Heat transfer, skin friction, turbulence intensity, and velocity profile data were obtained for 22 different rough surfaces in turbulent subsonic boundary layer air flow. The rough surfaces consisted of hemispherical dimples, hemispherical protrusions, and rectangular protrusions. The rectangular roughness plates were tested with the tops of the elements flush with the upstream smooth surface and with the tops protruding above the smooth-surface. The surfaces with protrusions were designed to have values of the Simpson roughness shape/spacing parameter that bracket the peak in the equivalent sand- grain correlation. The data was used for comparison with predictions from a discrete element rough surface boundary layer code in an attempt to improve the code's performance for cases of closely spaced roughness elements when wakes behind individual elements overlap. An anomaly was discovered in the code that causes wide variations In predicted drag and heat transfer for small variations in element drag coefficient Cd. The problem lies in the effect of Cd on the velocity calculation giving rise to inflections in the calculated velocity profile near the crests of the roughness elements. A remedy to the problem has not, as yet, been found. Turbulent boundary layer, Machined roughness, Subsonic.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1992
- Accession Number
- ADA256187
Entities
People
- D. E. Klett
- M. Kithcart
Organizations
- North Carolina Agricultural and Technical State University