Journal of Fluid Mechanics

The structure of turbulent boundary layers along mildly curved surfaces

B. R.  Ramaprian a1 and B. G.  Shivaprasad a2
a1 Institute of Hydraulic Research, University of Iowa, Iowa City
a2 Aeronautical Engineering Department, Indian Institute of Science, Bangalore

Article author query
ramaprian br   [Google Scholar] 
shivaprasad bg   [Google Scholar] 


This paper describes a detailed study of the structure of turbulence in boundary layers along mildly curved convex and concave surfaces. The surface curvature studied corresponds to δ/Rw = ± 0·01, δ being the boundary-layer thickness and Rw the radius of curvature of the wall, taken as positive for convex and negative for concave curvature. Measurements of turbulent energy balance, autocorrelations, auto- and cross-power spectra, amplitude probability distributions and conditional correlations are reported. It is observed that even mild curvature has very strong effects on the various aspects of the turbulent structure. For example, convex curvature suppresses the diffusion of turbulent energy away from the wall, reduces drastically the integral time scales and shifts the spectral distributions of turbulent energy and Reynolds shear stress towards high wavenumbers. Exactly opposite effects, though generally of a smaller magnitude, are produced by concave wall curvature. It is also found that curvature of either sign affects the v fluctuations more strongly than the u fluctuations and that curvature effects are more significant in the outer region of the boundary layer than in the region close to the wall. The data on the conditional correlations are used to study, in detail, the mechanism of turbulent transport in curved boundary layers.

(Published Online April 12 2006)
(Received September 27 1976)
(Revised July 18 1977)