**Prof. Dale Pullin**

Graduate Aeronautical Laboratories

California Institute of Technology

**"Vortex dynamics, turbulence and large-eddy simulation"**

**Abstract:**

Some aspects of the utility of vortex dynamics in the prediction of the properties of turbulence will be discussed. This will be followed by a brief outline of the large-eddy simulation (LES) method for the computation of turbulent flows at moderate to high Reynolds numbers. A vortex-dynamics approach to the modeling of subgrid turbulence scales for LES will be then be described. This is the `stretched-vortex', model in which the unresolved (subgrid) velocity field is modeled by nearly axisymmetric subgrid vortices - one or more per grid point - whose axis alignments are related to the local resolved-flow velocity gradients. The subgrid stresses produced by the vortices are proportional to the product of the vortex energy and a second-order tensor determined by the vortex axis directions. Applications of the model to decaying turbulence, incompressible turbulent channel flow at moderate Reynolds numbers, and to the statistics of a passive scalar in forced isotropic turbulence will be described.

#### Monday, May 1, 2000

3:00 PM in 335 Jabara Hall

Please join us for refreshments before the lecture at 2:30p.m. in room 353 Jabara Hall.

[ Spring 2000]