[GTP] MMM seminar of GTP interest -Julian Hunt

[Silvia Gentile]

Interfacial Layers in High-Re Turbulence-Physics and Simulations
Julian Hunt
University College London
Trinity College Cambridge
Technical University of Delft

Where turbulent flows with or without mean shear are adjacent to regions 
of very weak turbulence, such as boundary layers wakes, jets, and 
plumes, or convective layers, quasi-continuous interfacial layers tend 
to form that separate the turbulent and non-turbulent regions. 
Measurements and computations show that the mean and variance profiles 
of velocity and scalars have common global features, such as the outward 
‘boundary entrainment velocity’ and discontinuities of the Reynolds 
stresses. These features vary depending on the strength of the shear. 
Microscale vortices are common to most interfacial layers. These results 
can be explained in terms of key mechanisms, including instabilities, 
shear sheltering, and nibbling/engulfment, and energy transfer dynamics 
in the vicinity of the interfaces. Improvements in parameterizations and 
in under -resolved simulations are emerging.
Computations by Ishihara and Kaneda on the Earth Simulator at Rλ greater 
than 1000 and laboratory turbulence at Cambridge at Rλ up to 450 show 
how similar thin-layers occur intermittently in the interior of 
turbulent flows. But there are some important differences. Detailed 
analysis of the data and a rapid distortion model shows how the eddies 
impact on the layers leads to a net down scale transport, peak 
dissipation and microscale velocities of the order of the rms velocities 
in the layers. Some of the statistics are consistent with Kolmogorov theory.

***PLEASE NOTE SPECIAL DAY AND TIME***

Friday, 1 March 2013, 11:15 AM
Refreshments 11:00 AM
NCAR-Foothills Laboratory
3450 Mitchell Lane
Bldg 2 Auditorium, Room 1022

Silvia Gentile
NCAR IMAGe
1850 Table Mesa Drive
Boulder, CO 80305
303 497 2480
www2.image.ucar.edu



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