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Setting Up a Numerical Model of a DAF Tank: Turbulence, Geometry, and Bubble Size

Mia Bondelind (Institutionen för bygg- och miljöteknik, Vatten Miljö Teknik ; DRICKS Ramprogrammet för dricksvattenforskning vid Chalmers) ; Srdjan Sasic (Institutionen för tillämpad mekanik, Strömningslära) ; Thomas J. R. Pettersson (Institutionen för bygg- och miljöteknik, Vatten Miljö Teknik) ; Thodoris Karapantsios ; Margaritis Kostoglou ; Lars Bergdahl (Institutionen för bygg- och miljöteknik, Vatten Miljö Teknik)
Journal of Environmental Engineering (0733-9372). Vol. 136 (2010), 12, p. 1424-1434.
[Artikel, refereegranskad vetenskaplig]

This paper discusses the modeling framework and identifies a number of parameters relevant when setting up a computational fluid dynamics simulation of a dissolved air flotation (DAF) tank. The selection of a turbulence model, the choice between performing two-dimensional (2D) or three-dimensional (3D) simulations, the effects of the design of the flow geometry and the influence of the size of the air bubbles are addressed in the paper. The two-phase flow of air and water is solved in the Eulerian-Lagrangian frame of reference. The realizable k- model with nonequilibrium wall functions is suggested as a compromise between a need to effectively resolve the flow and the cost of the simulations. There is a discussion on the conditions for which the steady-state simulations are appropriate. We demonstrate that a steady 2D model can simulate a stratified flow pattern. Our results show that 2D models require adjustments in geometry (e.g., substitution of the outlet pipes to an outlet distributed over the total width of the tank) and in the parameters governing the flow in order to account for the true 3D nature of some of the flow patterns. In addition, we show that the bubble size has a larger influence on the flow in the separation zone than in the contact zone.

Nyckelord: Dissolved air flotation, DAF, CFD, computational fluid dynamics, multiphase, turbulence, Flow simulation, Two phase flow, Water tanks, Drinking water, Water treatment, Numerical models, Bubbles

Denna post skapades 2010-11-16. Senast ändrad 2015-07-02.
CPL Pubid: 129168


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