Library Subscription: Guest
TSFP DL Home Archives Executive Committee

ANISOTROPY OF THE ROUGH TURBULENT BOUNDARY LAYER SUBJECT TO A FAVORABLE PRESSURE GRADIENT

Raul Bayoan Cal
Department of Mechanical Engineering, The Johns Hopkins University, 3400 N. Charles St., Baltimore, Maryland 21218, USA

Brian Brzek
Department of Mechanical, Aeronautical and Nuclear Engineering, Rensselaer Polytechnic Institute, 110 8th st. Troy, New York 12180, USA

Gunnar Johansson
Department of Applied Mechanics, Chalmers University of Technology, Horsalsvagen 7, SE-412 96 Goteborg, Sweden

Luciano Castillo
Department of Mechanical Engineering, Aeronautical Engineering & Mechanics Rensselaer Polytechnic Institute Troy, NY 12180 USA; Dept. Mech. Eng. Texas Tech University Lubbock, TX 79409-1021, USA

Abstract

Laser-Doppler anemometry (LDA) measurements of the mean velocity and Reynolds stresses are carried out on a rough surface favorable pressure gradient (FPG) turbulent boundary layer. These data are compared with smooth FPG turbulent boundary layer data possessing the same strength of pressure gradient and with rough zero pressure gradient (ZPG) data. In order to properly capture the x -dependence of the single point statistics, consecutive measurements of 11 streamwise locations were performed. It is observed through the anisotropy coefficients that the isotropy of the flow is promoted by both the rough surface and the pressure gradient. The isotropization of the boundary layer close to the wall is increased by the roughness, while on the outer part of the boundary layer it is caused by the favorable pressure gradient imposed on the flow. It is also shown through the production terms that the roughness causes a greater production of the turbulence on the outer flow.