Surface roughness effects:

This activity has been one of the main research fields for this group since about 1985. It started as a computational-turbulence modeling activity, but has been concentrated on experimental studies since 1990, when it became evident that the effect of surface roughness on the flow turbulence is probably too complicated to allow realistic simulations with the state of the art turbulence models. Different surface geometries have been used to generate the roughness effects. The first surface applied (a regularly spaced mesh grid) showed that the surface condition significantly alters the flow anisotropy and that the inner-outer layer interaction is much stronger than assumed in classical turbulence modelling. The second surface (consisting of transverse circular rods) showed that the flow structure is highly dependent on the topology of the roughness elements. For different roughnesses which produce the similar mean flow profiles, significantly different stress profiles may be found, so that only calculations which use detailed descriptions of the individual roughness elements may be expected to perform well on arbitrary surfaces.

Most of the experimental work has been undertaken as a collaboration with the University of Newcastle, New South Wales, Australia.

Modification of the van Driest damping function to include the effects of surface roughness P.-Å. Krogstad AIAA J., Vol. 29, 1991	Comparison between rough- and smooth-wall turbulent boundary layers P.-Å. Krogstad, R. A. Antonia and L. W. B. Browne J. Fluid Mechanics, Vol. 245, 1992
Structure of turbulent boundary layers on smooth and rough walls P.-Å. Krogstad and R. A. Antonia J. Fluid Mechanics, Vol. 277, 1994	Heat flux measurements in a turbulent boundary layer on a rough wall H. S. Shafi, R. A. Antonia and P.-Å. Krogstad Int. J. Heat and Mass Transfer, Vol. 40, 1997
Surface roughness effects in a turbulent boundary layer P.-Å. Krogstad and R. A. Antonia Experiments in Fluids, Vol. 27, 1999	An experimental and numerical study of channel flow with rough walls P.-Å. Krogstad, H.I. Andersson, O.M. Bakken and A. Ashrafian J. Fluid Mechanics, Vol. 530, 2005

Other related references:

Scaling of the bursting period in turbulent rough wall boundary layers

R. A. Antonia and P.-Å. Krogstad, Experiments in Fluids, Vol. 15, 1993

The use of orthogonal X-wire arrays for structure investigation in a turbulent boundary layer

P.-Å. Krogstad, R. A. Antonia and L. W. B. Browne, Experiments in Fluids, Vol. 15, 1993

Combined effect of wall suction and riblets on a low Re turbulent boundary layer

L. Djenedi, R. A. Antonia, J. Hundseid and P.-Å. Krogstad, The Aeronautical J., 1998

Turbulent transport of the Reynolds stresses above a rod-roughened boundary layer

R. Smalley, P.-Å. Krogstad and R. A. Antonia, 13th Australasian Fluid Mechanics Conference, Melbourne, 1998

Quadrant analysis of rough and smooth surface channel flows

O.M. Bakken and P.-Å. Krogstad, Turbulent Shear Flow Phenomena Conference 3, Stockholm, 2001

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