Accession Number:

ADA256187

Title:

Uniform Roughness Studies

Descriptive Note:

Final rept. 30 Sep 1987-20 Mar 1992

Corporate Author:

NORTH CAROLINA AGRICULTURAL AND TECHNICAL STATE UNIV GREENSBORO DEPT OF MECHANICAL ENGINEERING

Personal Author(s):

Report Date:

1992-05-01

Pagination or Media Count:

83.0

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 shapespacing 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 codes 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.

Subject Categories:

  • Fluid Mechanics
  • Mechanics
  • Thermodynamics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE