Subpipe Project
Abstract
The purpose of this project was to examine the effect of surface roughness on a turbulent wall flow, in the limit of small roughness. It is, in effect, an attempt to throw light on experimental results dating from 1933, which appear to have been misinterpreted ever since as the result of an imprecise statement in the original (German) report by Nikuradse (a.k.a. Nikuradze) and its translations. It was stated that below a certain Reynolds number, based on the (sand-grain) roughness height and the friction velocity, the roughness had "no effect" on the friction factor (i.e. no effect on the additive constant in the logarithmic law for velocity). All that can be deduced from the plotted results is that the effect became smaller than the experimental scatter, and there is no reason to suppose that the roughness effect depends on instability above some "critical" Reynolds number - particularly as later estimates of this Reynolds number are very low.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 2007
- Accession Number
- ADA481827
Entities
People
- Peter Bradshaw
Organizations
- Stanford University