  Passive scalars in turbulent channel flows are investigated as canonical
problem for heat and mass transfer in turbulent boundary-layer flows. The
one-dimensional turbulence model is used to numerically investigate the Schmidt
and Reynolds number dependence of the scalar transfer to a wall due to
fluctuating wall-normal transport. First, the model is calibrated for low-order
velocity statistics. After that, we keep the model parameters fixed and
investigate low-order passive scalar statistics for a relevant Schmidt and
Reynolds number range. We show that the model consistently predicts the
boundary layer structure and the scaling regimes, for which it is close to
asymptotic one-dimensional theory.
