Journal of Fluid Mechanics

Turbulent oscillatory boundary layers at high Reynolds numbers

B. L.  Jensen a1, B. M.  Sumer a1 and J.  Fredsøe a1
a1 Technical University of Denmark, Institute of Hydrodynamic and Hydraulic Engineering, 2800 Lyngby, Denmark

Article author query
jensen bl   [Google Scholar] 
sumer bm   [Google Scholar] 
fredsøe j   [Google Scholar] 


This study deals with turbulent oscillatory boundary-layer flows over both smooth and rough beds. The free-stream flow is a purely oscillating flow with sinusoidal velocity variation. Mean and turbulence properties were measured mainly in two directions, namely in the streamwise direction and in the direction perpendicular to the bed. Some measurements were made also in the transverse direction. The measurements were carried out up to Re = 6 × 106 over a mirror-shine smooth bed and over rough beds with various values of the parameter a/ks covering the range from approximately 400 to 3700, a being the amplitude of the oscillatory free-stream flow and ks the Nikuradse's equivalent sand roughness. For smooth-bed boundary-layer flows, the effect of Re is discussed in greater detail. It is demonstrated that the boundary-layer properties change markedly with Re. For rough-bed boundary-layer flows, the effect of the parameter a/ks is examined, at large values (O(103)) in combination with large Re.

(Published Online April 26 2006)
(Received December 19 1988)