Direct numerical simulations of the turbulent mixing of a passive scalar
Abstract
The evolution of scalar fields, of different initial integral length scales, in statistically stationary, homogeneous, isotropic turbulence is studied. The initial scalar fields conform, approximately, to ``doubledelta function'' probability density functions (pdf 's). The initial scalartovelocity integral lengthscale ratio is found to influence the rate of the subsequent evolution of the scalar fields, in accord with experimental observations of Warhaft and Lumley [J. Fluid Mech. 88, 659 (1978)]. On the other hand, the pdf of the scalar is found to evolve in a similar fashion for all the scalar fields studied; and, as expected, it tends to a Gaussian. The pdf of the logarithm of the scalardissipation rate reaches an approximately Gaussian selfsimilar state. The scalardissipation spectrum function also becomes selfsimilar. The evolution of the conditional scalardissipation rate is also studied. The consequences of these results for closure models for the scalar pdf equation are discussed.
 Publication:

Physics of Fluids
 Pub Date:
 March 1988
 DOI:
 10.1063/1.866832
 Bibcode:
 1988PhFl...31..506E
 Keywords:

 Computerized Simulation;
 Probability Density Functions;
 Reynolds Number;
 Scalars;
 Turbulent Flow;
 Turbulent Mixing;
 Computational Fluid Dynamics;
 Flow Distribution;
 Fluid Flow;
 NavierStokes Equation;
 Numerical Flow Visualization;
 Velocity Distribution;
 Fluid Mechanics and Heat Transfer