Self-Similar Properties of Boundary Layer
Turbulence at High Reynolds Numbers
Friday, January 27, 3:00 pm
Sidney & Marian Green Classroom (3550 MEK)
Free and open to the public
Joseph C. Klewicki, Ph.D.
Professor, Department of Mechanical Engineering
University of New Hampshire, and the
University of Melbourne, Victoria, Australia
Abstract: Turbulent flow in the immediate vicinity of a solid surface is of immense scientific and technological importance, since, for example, the dynamics of these flows dictate the transport of heat and momentum to or from the bounding surface. In this regard, the existence of a logarithmic mean velocity profile and the associated broader concept of a self-similar inertial region within turbulent wall-flows are foundational descriptors of wall-flow structure. Like Kolmogoroff’s theories, a log law with a constant leading coefficient, 1/k (k = von Karman constant) is viewed as a central achievement of turbulent flow theory in general. Unfortunately, the formulation of a rigorous basis for these behaviors is severely hindered by the indeterminacy of the time averaged equations of motion – giving rise to numerous hypotheses and assumptions (of either a mathematical or phenomenological nature) as to why these flow properties exist. Efforts over the past decade indicate, however, that direct multiscale analysis of the mean equation of motion is possible, once the underlying leading balance structure is known. In the present talk the essential elements of these analyses are described for the simpler channel flow, and for the more complicated zero pressure gradient turbulent boundary layer. It is shown that the mean equation admits a self-similar (invariant) form that analytically admits a log-law solution, with the value of the von Karman constant directly related to the coordinate stretching parameter (Fife similarity parameter, ф) required to express the mean equation in its self-similar form. Some surprising physical and geometric implications arise from the analytical structure revealed, and data from the large scale wind tunnels at the University of Melbourne and the University of New Hampshire, as well as from experiments in the atmospheric surface layer that forms over Utah’s salt playa are used to investigate the veracity of these findings.
Bio: Dr. Joe Klewicki is a Professor of Mechanical Engineering at the University of New Hampshire and the University of Melbourne. His research is in the area fluid dynamics, with emphases on experimental and theoretical studies of the structure, dynamics and Reynolds number scaling of turbulent wall-flows, vorticity dynamics in turbulent shear flows, and experimental methods. Dr. Klewicki previously served as Dean of the College of Engineering and Physical Sciences at the University of New Hampshire, and before that was the Chair of the Department of Mechanical Engineering at the University of Utah. He is the 19th ASME Freeman Scholar of Fluid Dynamics, a distinguished alumnus of Michigan State University, a member of the Australian Research Council College of Experts, and a fellow of the ASME and APS.