Computations of curved free surface water flow on spiral concentrators

Spiral concentrators, consisting of an open trough that twists vertically downward about a central axis, are used to separate radially a thin-film slurry of mineral and waste material on the basis of particle density and size. This paper reports the detailed steady and uniform flow results of a computational fluid dynamics model for the water phase. The flow is characterized by a free surface, shallow (1-14 mm) depths, radial transition to fully turbulent flow, and superimposed secondary motion. Validated results are presented for depths and primary and secondary velocity components, both internally and on the free surface. A detailed understanding of the flow behavior beyond that readily available by experimentation on the concentrator has been gleaned. More importantly, an efficient and fully predictive computational fluid dynamics methodology is demonstrated for the class of problems represented by the example, having wider relevance for hydraulic open channel applications. The model solves the Reynolds-averaged Navier-Stokes equations and employs the volume of fluid free surface method, isotropic k-[egr ] and Renormali- zation Group k-[egr ] turbulence formulations, and the wall function approach.