Spring Quarter 1999

ME/IE 8773-8774

LARGE EDDY SIMULATION OF SCALAR TRANSPORT IN TURBULENT JETS

by

Sean C. Garrick
Assistant Professor
Department of Mechanical Engineering
University of Minnesota 111 Church St. S.E.
Minneapolis, MN 55455-0111

Wednesday, May 5, 1999
1:25 - 2:15 p.m.
Room 102 ME
Broadcast on UNITE Channel B
Coffee will be available in 152 ME following the seminar

The "filtered density function" (FDF) methodology is implemented for large eddy simulations (LES) of three- dimensional round jet, under both non-reacting and chemically reacting conditions. In this methodology, the effects of the unresolved scalar fluctuations are taken into account by considering the probability density function (PDF) of the sub-grid scale (SGS) scalar quantities in a stochastic manner. The influences of scalar mixing and convection within the sub-grid are taken into account via conventional methods. The FDF transport equation is solved numerically via a Lagrangian Monte Carlo scheme in which the solutions of equivalent stochastic differential equations are obtained. Simulations of a round jet are performed in the proximal region In non-reacting flows, the FDF solution yields results similar to those via LES-FD for the first two SGS moments. The advantage of the FDF methodology is demonstrated by its use in LES of reacting flows. In the absence of a closure for the SGS scalar fluctuations, the traditional finite difference results are significantly different from those obtained by the FDF.

Prof. Sean Garrick received his Ph.D. degree in Mechanical from the State University of New York at Buffalo in 1998. He joined the faculty of the Mechanical Engineering Department at the University of Minnesota in Fall 1998. His research is in the area of large eddy simulation (LES) of turbulent reacting flows. LES facilitates the solution of the spatially (and/or temporally) filtered governing equations. The filtering procedure presents the problem of turbulence closure, for the unresolved sub grid scale (SGS) quantities in both the hydrodynamic, and the species transport, equations. Current efforts are focused on probability density function (PDF) methods. In this approach, transport of the chemical species is considered in a probabilistic manner. The SGS PDF, or the filtered density function (FDF) is essentially the PDF of the SGS scalar variables. The species are represented by a joint FDF. In the transport equation governing the evolution of the FDF, the effects of chemical reactions appear in a closed form. Such a robust methodology has applications in high-speed air breathing propulsion, gas turbine engines, internal combustion engines, biomass reactors, to name a few. Simulations are performed on supercomputers located at the Minnesota Supercomputing Institute.

Informal Faculty Luncheon: Wednesday, May 5, 1999, 11:45 am, Room 404, Campus Club. Prof. Garrick will be able to attend.