Numerical prediction of three-dimensional mixing in a compound open channel

Abstract

A numerical model has been developed to simulate time-dependent turbulent flows in open channels, including the transport of dissolved materials. The turbulence closure is provided by two algebraic eddy viscosity models. This paper's main focus is on the assessment of those two models' predicting capabilities for an open channel with compound cross section. A three-dimensional turbulent flow field and the transport of a neutrally buoyant solute are modeled. The results of the simulation are compared with experimental data and with similar calculations obtained using more advanced turbulence models. Considerations are made regarding the choice of the appropriate Schmidt number for the modeling of turbulent mass transport, and the use of anisotropic eddy diffusivity to account for different mixing rates along the vertical and transverse directions. Conclusions are drawn regarding the accuracy of the two models and their advantages and drawbacks when compared with more advanced turbulence models.