A complete second-order closure model of turbulence is used to predict
the behavior of fully developed turbulent flows in open channels of b
oth simple and compound cross sections. This level of closure entails
the solution of seven differential transport equations for turbulence
quantities and is found to reproduce fairly accurately the details of
the turbulence-driven secondary motions that occur in the cross-stream
planes. In particular, the number, location, and strength of the seco
ndary-flow cells are well predicted, as is their effect on the bulk pr
operties of the mean flow. Data from simple rectangular channels are u
sed to check the model's sensitivity to the effects of a free surface,
and data from compound channels, both symmetric and asymmetric, serve
to validate the model for a range of parameters typical of those enco
untered in practice.