Search

The deposition of non-Brownian particles from turbulent liquid-flow onto channel walls is numerically analyzed. The approach combines Lagrangian particle tracking with a kinematic model of the near-wall shear layer. For nonbuoyant particles, direct interception is the main deposition mechanism and the deposition velocity scales as the particle diameter (in wall units) to the power of 1.7. When wall/particle hydrodynamic interactions are taken into account, the deposition velocity is significantly reduced and the correction factor scales as the cubic root of the wall roughness to particle diameter ratio. For buoyant particles, sedimentation is usually the predominant deposition mechanism and the hydrodynamic interactions significantly affect the deposition velocity when the drainage characteristic time driven by buoyancy is of the order of the particle residence time close to the wall. Last, a wall-function for the suspended particles is proposed. © 2015 American Institute of Chemical Engineers AIChE J, 62: 891-904, 2016 [ABSTRACT FROM AUTHOR]

A two-dimensional mathematical model of the initial stage of depth filtration is developed. This model describes the fluid flow and the particle transport and capture in a representative elementary volume of the filter. A typical simulation can be outlined as follows: as a first stage, the flow field is computed in the whole complex void space of the filter using a lattice-Boltzmann method. As a second stage, the trajectory analysis is derived by applying Newton's second law to suspended particles in the flowing fluid. The capture or the reentrainment of the particles encountering the filter surface is determined from a force balance that takes into account the drag force and the solid friction force. This approach, which provides both microscopic data such as the initial capture probability density and macroscopic data such as the filter coefficient, is validated on a model experiment of deep-bed filtration. [ABSTRACT FROM AUTHOR]