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.