AN EXPERIMENTAL STUDY OF TURBULENT BOUNDARY LAYER ON ROUGH WALLS,
Abstract
Experimental data are presented on flow structure, mean, and fluctuating velocities in turbulent boundary layers over a family of flat surfaces with transverse roughness elements made of square bars of variable spacing. All flows were incompressible and had zero streamwise pressure gradient. The flow structures are described for surfaces extending from hydraulically smooth to fully rough. A distinct flow pattern is observed in the wall region for each of four cases: smooth, skimming, wake-interference and isolated-roughness flow. Maximum roughness was observed with a ratio of gap to bar width of approximately 11. The most obvious effect of an increase in surface roughness is the distinct increase of turbulence production and the concomittant increase in the value of eddy viscosity. It is shown that this increase in eddy viscosity increases the total thickness of the layer in the same way that an increase in molecular viscosity would do in a laminar layer. The normalization of eddy viscosity for the outer portion of the layer as suggested by Clauser is found to apply to the rough surfaces studied. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1966
- Accession Number
- AD0647268
Entities
People
- C. K. Liu
- J. P. Johnston
- S. J. Klein
Organizations
- Stanford University