Simulation of fluid suspended particle behaviour subject to transverse standing acoustic fields
type: CreativeWork
description: The computational study addressed the effectiveness with which a standing wave acoustic field could be used to deflect quartz particles carried in water at 20Â°C through a simple parallelepiped control volume representative of a vertically orientated duct geometry dimensioned 50 Ã— 50 Ã— 70 cm 3 , with square base. An acoustically driven planar standing wave field produces quasi-static oscillatory pressure gradients within resonant cavities, which are responsible for acoustic forces, which act on particles, located within the acoustic field. These forces drive particles to nodal (no fluctuation) or anti-nodal (continuous fluctuation) planes of pressure. Standing wave fields are generally produced by a transducer driving into a fluid through an adhesively bonded matching layer. The wave is reflected at the opposite boundary layer terminating in an air backing. The chamber is dimensioned so as to produce constructive wave interference between the two waves travelling in opposite directions. The acoustic force has been used in small scale filtration systems to deflect particles and on larger scales as a pre filtration agglomerator clumping very small particles which are otherwise poorly filtered in isolation by conventional methods. The study was twofold, in that a major component of the study comprised developing the architecture of the computational model, the other part comprising qualitative model validation through parameter variation. The study involved coupling between Computational Fluid Dynamics (CFD) Software (OpenFOAM) and Discrete Element Modelling (DEM) Software (LIGGGHTS), through a coupling code (CFDEM) built as an extension to OpenFOAM and tailored for LIGGGHTS. The acoustic field was assumed ideal i.e. in a lossless medium with perfect reflection at the opposite wall. Particle-particle and particle-wall collisions were circumvented by using larger time increments, inadequate to resolve col- lisions, and inserting particles in the bulk of the flow away …
abstract: The computational study addressed the effectiveness with which a standing wave acoustic field could be used to deflect quartz particles carried in water at 20Â°C through a simple parallelepiped control volume representative of a vertically orientated duct geometry dimensioned 50 Ã— 50 Ã— 70 cm 3 , with square base. An acoustically driven planar standing wave field produces quasi-static oscillatory pressure gradients within resonant cavities, which are responsible for acoustic forces, which act on particles, located within the acoustic field. These forces drive particles to nodal (no fluctuation) or anti-nodal (continuous fluctuation) planes of pressure. Standing wave fields are generally produced by a transducer driving into a fluid through an adhesively bonded matching layer. The wave is reflected at the opposite boundary layer terminating in an air backing. The chamber is dimensioned so as to produce constructive wave interference between the two waves travelling in opposite directions. The acoustic force has been used in small scale filtration systems to deflect particles and on larger scales as a pre filtration agglomerator clumping very small particles which are otherwise poorly filtered in isolation by conventional methods. The study was twofold, in that a major component of the study comprised developing the architecture of the computational model, the other part comprising qualitative model validation through parameter variation. The study involved coupling between Computational Fluid Dynamics (CFD) Software (OpenFOAM) and Discrete Element Modelling (DEM) Software (LIGGGHTS), through a coupling code (CFDEM) built as an extension to OpenFOAM and tailored for LIGGGHTS. The acoustic field was assumed ideal i.e. in a lossless medium with perfect reflection at the opposite wall. Particle-particle and particle-wall collisions were circumvented by using larger time increments, inadequate to resolve col- lisions, and inserting particles in the bulk of the flow away …
author: Dabic, Mihajlo
language: eng
date published: 2012
date modified: 2026-07-22T22:23:36Z
provider: University of Cape Town
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Department of Chemical Engineering

PropertyValue
property ID: Handle
value: http://hdl.handle.net/11427/14562