Journal of Fluid Mechanics



Topology of a turbulent boundary layer with and without wall suction


R. A.  Antonia a1 and L.  Fulachier a2
a1 Department of Mechanical Engineering, University of Newcastle, New South Wales, 2308, Australia
a2 Institut de Mécanique Statistique de la Turbulence, Université d'Aix-Marseille 13003, Marseille, France

Article author query
antonia ra   [Google Scholar] 
fulachier l   [Google Scholar] 
 

Abstract

Measurements of velocity and temperature fluctuations are made in a turbulent boundary layer with nominally zero pressure gradient for two different slightly heated wall conditions: impermeable and porous surfaces. The temperature fluctuations are measured at three points in the flow to permit the identification of two spatially coherent events: coolings and heatings. Conditional velocity vectors in the plane of mean shear are viewed in a reference frame which translates at a constant velocity. Conditioning is on coolings, heatings or a combination of these events. Sectional streamlines, derived from the velocity vector data, show a succession of critical points: saddles and unstable foci. Coolings are aligned with diverging separatrices through the saddles whereas heatings are identified with the foci. Coolings are associated with a large strain rate and also a large spanwise vorticity: this result seems consistent with the presence of hairpin vortices which extend to different distances from the wall. In contrast, the strain rate and spanwise vorticity are small at the foci. The stabilizing influence of suction is observed in the topology of the organized motion and in the contribution from this motion to the conventional stresses, temperature variance and heat fluxes.

(Published Online April 21 2006)
(Received November 25 1987)
(Revised June 28 1988)



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