A SIMPLE THEORY OF CONDITIONAL MEAN VELOCITY IN TURBULENT SCALAR-MIXING LAYER

This paper presents the experimental results on conditional mean trans verse velocity across a turbulent scalar mixing layer. The velocity is conditioned on mixture fraction. It is found that the distribution of the conditional mean transverse velocity is closely related to the lo cal mean-mixture fraction in physical space. Near the local mean-mixtu re fraction a linear relationship exists between the conditional mean transverse velocity and the mixture-fraction fluctuations. Departure f rom the linear relationship at large mixture-fraction fluctuations is mainly due to the nonlinear distribution of the mean mixture-fraction profile and it is not, as has been suggested by others, due to the lim iting velocity of the large eddies in the flow.