Setting Up a Numerical Model of a DAF Tank: Turbulence, Geometry, and Bubble Size
Artikel i vetenskaplig tidskrift, 2010

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.




Flow simulation

Numerical models

Drinking water

Water tanks

Dissolved air flotation



computational fluid dynamics

Water treatment

Two phase flow


Mia Bondelind

Chalmers, Bygg- och miljöteknik, Vatten Miljö Teknik

DRICKS Ramprogrammet för dricksvattenforskning vid Chalmers

Srdjan Sasic

Chalmers, Tillämpad mekanik, Strömningslära

Thomas Pettersson

Chalmers, Bygg- och miljöteknik, Vatten Miljö Teknik

Thodoris Karapantsios

Aristotelio Panepistimio Thessalonikis

Margaritis Kostoglou

Aristotelio Panepistimio Thessalonikis

Lars Bergdahl

Chalmers, Bygg- och miljöteknik, Vatten Miljö Teknik

Journal of Environmental Engineering, ASCE

0733-9372 (ISSN)

Vol. 136 12 1424-1434



Annan naturresursteknik

Strömningsmekanik och akustik



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