Computations of curved free surface water flow on spiral concentrators

Spiral concentrators, consisting of an open trough that twists vertically d ownward about a central axis, are used to separate radially a thin-film slu rry of mineral and waste material on the basis of particle density and size . This paper reports the derailed steady and uniform flow results of a comp utational fluid dynamics model for the water phase. The flow is characteriz ed by a free surface, shallow (1-14 mm) depths, radial transition to fully turbulent flow, and superimposed secondary motion. Validated results are pr esented for depths and primary and secondary velocity components, both inte rnally and on the free surface. A detailed understanding of the flow behavi or beyond that readily available by experimentation on the concentrator has been gleaned. More importantly, an efficient and fully predictive computat ional fluid dynamics methodology is demonstrated for the class of problems represented by the example, having wider relevance for hydraulic open chann el applications. The model solves the Reynolds-averaged Navier-Stokes equat ions and employs the volume of fluid free surface method, isotropic k-epsil on and Renormalization Group k-epsilon turbulence formulations, and the wal l function approach.