Mono- and multi-diameter approaches to predict stratified flow structure by means of CFD simulations in DAF systems

This paper presents a Computational Fluid Dynamics (CFD) model of pilot scale dissolved air flotation (DAF) tank. A Multiphase Mixture was used to analyse the influence bubble sizes on formation stratified flow structure. Critical diameter is defined as size that implies equality rising velocity and downward in separation zone (SZ). The fact whether using which are greater or less than critical value significantly affects content, structure limit whitewater blanket inside SZ assessed. study carried out two approaches, namely, mono- multi-diameter. results obtained via mono-diameter approach proved be closely line with experimental data when concentration had almost, but not quite, constant value. However, it failed predict case progressive decrease below half height. combined effect bubbles different speed required reproduce smooth profile curve, measured experimentally. In this context, multi-diameter deemed suitable method for reproducing addition, offers chance distribution domain. • "Critical diameter” explained distinct types hydrodynamic behaviour seen CFD provided good prediction uniform capable forecasting Steady-state sufficiently long transient simulations equivalent Euler-Euler models equally valid DAF