Influence of wall roughness on particle deposition in a circular tube

The influence of wall roughness on particle deposition and transport in mini/micro-scale tubes is of importance in estimating the concentration distribution or mean concentration of particulate matter. The principle of equivalent smooth wall is utilized to characterize the wall roughness in constructing the physical model of particle transport and deposition due to convection, diffusion, and gravity in a tube with rough inner surface under the plug flow regime, and analytic expression for concentration distribution is presented in this study. The analytical solutions agree well with the experiments and are several orders of magnitude faster than numerical difference methods. The results reveal that wall roughness exerts a spatially dependent influence on particle concentration due to the coupling effects of diffusion and sedimentation. The impact of surface roughness on mean concentration is related to the dimensionless parameters and diminishes with the increase in deposition parameter and axial distance. The analytical expressions obtained in this study can be used to estimate the particle deposition efficiency in some mini/micro-scale fluidic systems of sampling pipelines, respiratory airway drug delivery, and exhaust gas purification devices.