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Selected Works

1992

Rodney O. Fox

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The Fokker–Planck Closure For Turbulent Molecular Mixing: Passive Scalars, Rodney O. Fox Jun 1992

The Fokker–Planck Closure For Turbulent Molecular Mixing: Passive Scalars, Rodney O. Fox

Rodney O. Fox

A turbulent-molecular-mixing closure for passive scalar mixing is derived based on the theory of diffusion in layerlike lamellar structures. The closure is formulated in terms of the Fokker- Planck (FP) equation (or an equivalent stochastic differential equation), and is to be employed in conjunction with the probability density function (pdf) balance equation appearing in the pdf methods for modeling turbulent reactive flows. Like the mapping closure, the FP closure predicts a limiting Gaussian pdf for the passive scalar concentration in isotropic turbulence. In addition, the FP closure models the joint pdf of the scalar concentration and the scalar gradient and ...


Stochastic Modeling Of Turbulent Reacting Flows, Rodney O. Fox, J. C. Hill, F. Gao, R. D. Moser, M. M. Rogers Jan 1992

Stochastic Modeling Of Turbulent Reacting Flows, Rodney O. Fox, J. C. Hill, F. Gao, R. D. Moser, M. M. Rogers

Rodney O. Fox

Direct numerical simulations of a single-step irreversible chemical reaction with non-premixed reactants in forced isotropic turbulence at Rx = 63, Da = 4.0, and Sc = 0.7 were made using 128 Fourier modes to obtain joint pdfs and other statistical information to parameterize and test a Fokker-Planck turbulent mixing model. Preliminary results indicate that the modeled gradient stretching term for an inert scalar is independent of the initial conditions of the scalar field. The conditional pdf of scalar gradient magnitudes is found to be a function of the scalar until the reaction is largely completed. Alignment of concentration gradients with local ...