A Model for Removal of Compact,Rough, Irregularly Shaped Particles from Surfaces in Turbulent Flows

A model for removal of compact, rough, irregularly shaped particles from surfaces in turbulent flow was developed. Following the approach of our previous bumpy particle model, irregularly shaped particles were modeled as spherical particles with a number of bumps on them. To improve the model, the effect of surface roughness was added to the bumps. Each bump was modeled with large number of asperities and the Johnson-Kendall-Roberts (JKR) adhesion theory was used to model the adhesion and detachment of each bump and asperity in contact with the surface. The total adhesion force for each bump was obtained as the summation of each asperity force in contact with the substrate. To account for the variability observed in the removal of particles, the number of bumps and roughness values of particles are assumed to be random, respectively, with Poisson and log-normal distributions. For particle separation from the surface, the theory of critical moment was used, and the orientation of bumps on the surface was considered when determining the range of shear velocity needed for removal of the irregularly, shaped particles. The effects of particle size, turbulent flow, particle irregularity, and particle surface roughness on detachment and resuspension were studied for different particles and surfaces. Model prediction for removal of rough, irregularly shaped graphite particles from steel substrate was compared with the available experimental data and earlier numerical models, and good agreement was obtained. This study may find application in adhesion and detachment of irregular particles from flooring in indoor and outdoor environments.