Published In

Fluid/Particle Separation Journal

Document Type


Publication Date



Separation (Technology) -- Mathematical models, Density currents, Sewage clarifiers, Hydrodynamics -- Computer simulation


Design of sedimentation tanks for solid-liquid separation is often dependent on assuming ideal flow conditions. But the geometry of the tank and density currents as a result of temperature and suspended solids influences the fluid mechanics of the tank and can result in significant deviations from ideal flow.

A two-dimensional radial flow model was proposed which incorporated the effect of density currents resulting from temperature and suspended solids differentials within the tank. The numerical model predicted the steady-state, layer-averaged radial flow and layer depth.

The model solution and field data showed that the momentum and suspended solids of the inflow caused a density current that moved along the clarifier bottom. In the winter, this density current rose as a result of warm inflow water after the initial momentum had decreased and the suspended solids had settled.


Author's version of a paper that was subsequently published in the Fluid/Particle Separation Journal, Vol. 11, No. 1, 48-54 (1998).

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