ADVANCES IN PDF MODELING FOR INHOMOGENEOUS TURBULENT FLOWS

Probability density function (PDF) models which are based on an exact representation of rapidly distorting homogeneous turbulence are applie d to a free shear flow, the temporal mixing layer. These velocity wave -vector models were constructed in a previous paper by Van Slooten and Pope [Phys. Fluids 9, 1085 (1997)], but were only tested in cases of homogeneous turbulence. At the edges of free shear flows both turbulen t-nonturbulent intermittency and pressure transport are demonstrated t o play a significant role in the behavior of the flow. A natural treat ment of intermittency is obtained by extending the PDF formulation to include a model for the turbulent frequency following a fluid particle . A model for the pressure transport is also constructed via a scaling analysis. The resulting velocity wave-vector turbulent-frequency PDF model with the pressure transport model yields a good comparison with the available direct numerical simulation data for the temporal shear layer. (C) 1998 American Institute of Physics.