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Licentiate seminar

Subgrid-scale modelling for large-eddy simulation invluding scalar mixing in rotating turbulent shear flows


Defendant Main Advisor Extra Advisor Date
Linus Marstorp Arne Johansson Geert Brethouwer 2006-04-28

Opponent
Lars-Erik Eriksson, Volvo Flygmotor AB, Trollhättan

Evaluation committee

Abstract

The aim of the present study is to develop subgrid-scale models that are relevant for complex flows and combustion. A stochastic model based on a stochastic Smagorinsky constant with adjustable variance and time scale is proposed. The stochastic model is shown to provide for backscatter of both kinetic energy and scalar variance without causing numerical instabilities. A new subgrid-scale scalar flux model is developed using the same kind of methodology that leads to the explicit algebraic scalar flux model, EASFM, for RANS. The new model predicts the anisotropy of the subgrid-scales in a more realistic way than the eddy diffusion model. Both new models were tested in rotating homogeneous shear flow with a passive scalar. Rogallo’s method of moving the frame with the mean flow to enable periodic boundary conditions was used to simulate homogeneous shear flow.
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