Frick, W. E. Ecosystems Research Division, Athens, USEPA,
Sigleo, A. C. US Environmental Protection Agency,

Mixing of fluids across boundary layers is a ubiquitous and critical natural process. Sophisticated computer models operating on closely spaced grids exist that simulate these processes. These models depend on parameterizing turbulence, that is, on relating mixing to other, often average, characteristics of the flow. While the results are increasingly realistic, these closure schemes are frequently intellectually remote and offer little in terms of intuitive understanding of the mixing process, particularly with respect to the nonlinear terms in the Navier-Stokes equations. An analysis of expanding radial flow between parallel plates offers a model for understanding the low pressure that develops between them. Consideration of mass and momentum conservation explains the attraction experienced by the plates. Such a device is sometimes used to demonstrate the Bernoulli theorem. The generalization of the problem, i.e., the removal of the plates, leads to a conceptual model of mixing at boundary layers. The model explains entrainment into plumes and other boundary layer phenomena, and serves as a starting point to express the mixing process at many scales. The model proves useful in conveying to students an intuitive understanding of mixing and provides a mechanism for disseminating plankton and nutrients from source regions such as upwelling.
Day: Wednesday, Feb. 3
Time: 08:30 - 08:45am
Location: Eldorado Hotel
Code: SS03WE0830E