Wall Turbulence: Attached Eddies, Packets and Scaling Issues

Department of Aerospace Engineering and Mechanics
University of Minnesota

Abstract-
Over the past several decades an increased awareness has grown about the role coherent vortex structures play in incompressible turbulent boundary layers. In this seminar, a physical model will be outlined which gives a kinematic description of turbulent boundary layers in terms of an assemblage of attached eddies. The formulation is used to compute statistical quantities such as two-point space correlation functions, spectra and Reynolds stresses. Quantitative comparisons are made with experimental data and support is given for the scenario where in the logarithmic region of the flow, the main structures are long streamwise, spatially correlated trains or packets of eddies. Related issues of Reynolds number scaling laws for the turbulence intensities are also considered and some preliminary results from high Reynolds number experiments on the salt-flats of Utah will be presented.

A brief consideration will also be given to the potential use of this physical model for supersonic boundary layer flows. Visualization results will be presented using the DNS data of Martin and Candler of a Mach 4 turbulent boundary layer.

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