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Large scale motions having
streamwise extent of the order of the thickness of the turbulent flow,
delta, and scaling with the outer variable are known to contain a
large fraction of the streamwise turbulent kinetic energy. But, they
are not thought to contribute very much to the Reynolds shear stress -
hence Townsend's (1976) designation of delta-scale motions as
"inactive". PIV experiments show that, contrary to conventional
wisdom, the delta-scale modes make a substantial contribution to the
total shear stress. Studies of Reynolds shear stress co-spectra reveal
two clearly separated modes, one consisting of the delta-scale modes
and the inertial subrange, and the other consisting of super-delta
scales, i.e. scales much longer than the boundary thickness.
Ronald J. Adrian was educated at
the University of Minnesota (B.M.E. 1967, M.S. 1969) and at Churchill
College, Cambridge, where he received his Ph.D. degree in physics in
1972. He is a member of Department of Theoretical and Applied
Mechanics at the University of Illinois, Urbana-Champaign where he
holds the Hoeft Chair in Engineering and is the Director of the
Laboratory for Turbulence and Complex Flow. His research interests are
the space-time structure of turbulent fluid motion and the development
of techniques, both experimental and mathematical, to explore this
structure. Methods to which he has made fundamental contributions are
the laser Doppler velocimeter technique, the method of particle image
velocimetery and the stochastic estimation method. He co-edited
Experiments in Fluids, and a ten volume series on Laser Techniques in
Fluid Mechanics, and currently, he serves as an Associate Editor of
the Journal of. Fluid Mechanics. His awards have included two SAE
Colwell Merit Awards, a U.S. Churchill Foundation Award, and the
Nusselt-Reynolds Prize. He is a past Chairman of the American Physical
Society Division of Fluid Dynamics, and the US National Committee on
Theoretical and Applied Mechanics. He is a Fellow of the American
Physical Society, the American Academy of Mechanics and ASME, and he
is a member of the United States National Academy of Engineering.
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