Accession Number:

ADA535047

Title:

Review of Hydraulic Roughness Scales in the Fully Rough Regime

Descriptive Note:

Journal article

Corporate Author:

NAVAL ACADEMY ANNAPOLIS MD DEPT OF MECHANICAL ENGINEERING

Personal Author(s):

Report Date:

2010-04-01

Pagination or Media Count:

11.0

Abstract:

A review of predictive methods used to determine the frictional drag on a rough surface is presented. These methods utilize a wide range of roughness scales, including roughness height, pitch, density, and shape parameters. Most of these scales were developed for regular roughness, limiting their applicability to predict the drag for many engineering flows. A new correlation is proposed to estimate the frictional drag for a surface covered with three-dimensional, irregular roughness in the fully rough regime. The correlation relies solely on a measurement of the surface roughness profile and builds on previous work utilizing moments of the surface statistics. A relationship is given for the equivalent sandgrain roughness height as a function of the root-mean-square roughness height and the skewness of the roughness probability density function. Boundary layer similarity scaling then allows the overall frictional drag coefficient to be determined as a function of the ratio of the equivalent sandgrain roughness height to length of the surface.

Subject Categories:

  • Statistics and Probability
  • Fluid Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE