AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Development of a Particle Resuspension Modelling Capability within a Computational Fluid Dynamics Framework
SARAH WILLIAMSON, Sarah Harrison, Jonathan Hill, John Locke, Defence, Science and Technology Laboratory, UK
Abstract Number: 658 Working Group: Indoor Aerosols
Abstract Aerosol particles that settle onto surfaces might later be lifted off or “resuspended” through various means. This resuspension of previously deposited particles is an important area of research as it may produce health consequences and affect decontamination procedures. The first objective of this study was to incorporate a resuspension model into a computational fluid dynamics (CFD) model, an example of which is demonstrated by simulating a helicopter approaching the ground. The second objective was to conduct small scale experiments to validate the resuspension model.
To understand resuspension it is necessary to consider the adhesive forces holding the particle to the surface and those forces which cause the particle to be removed. An algorithm has been developed to predict resuspension based on the work of Biasi et al[1]. This uses the “rock ‘n’ roll” theory whereby a combination of lift and drag forces overcome the force of adhesion between the particle and the surface, causing the particle to resuspend. The model has been shown to behave qualitatively as expected.
The resuspension model has been incorporated into CFD software ANSYS® Fluent®, for the simulation of a helicopter vertically descending towards the ground. The model predicts that the resulting flow is strong enough to cause a significant proportion of particles to be resuspended. The fraction of material resuspended from each computational cell at each time step is output by the model.
Small scale experiments have been designed to quantitatively validate the resuspension model. A bench top wind tunnel, fitted with a microscope and video camera, allows particles and their resuspension to be monitored. A silicon wafer surface was analysed before and after the experiments to determine the proportion of silica particles removed. The experimentally measured resuspension will be compared to the model output to validate the resuspension model.
[1] Biasi et al. Aerosol Science, 32, 1175-1200, 2001.