Modelling Particle Deposition in a Turbulent Ribbed Channel Flow

Transport and deposition of aerosol particles in a plane channel with a ribbed wall are studied to investigate the effects of turbulent flow structure on particle deposition. We introduce a novel particle tracking model namely kinematic simulation (KS) [1], which is a Lagrangian model of turbulent dispersion that takes into account the effects of spatio-temporal flow structure on particle dispersion. It is a unified Lagrangian model of one-, two- and indeed multi-particle turbulent dispersion and can easily be used as a Lagrangian sub-grid model for large eddy simulation (LES) code thus enabling complex geometry to be taken into account. To study the effect of small scale flow structure on particle deposition in the ribbed channel flow we use a validated LES code [2] to simulate the flow filed, and KS to model the sub-grid flow structure to generate particle trajectories. Thus the large scales are resolved by the simulation and the small scales are modelled using various sub-grid models. As none of the existing sub-grid models are known to have taken into account the effects of small-scale turbulent flow structures on particle deposition, it is important to use KS’s ability to re-model the sub-grid velocity field and thereby incorporate its effect on particle deposition. The parameters of our simulations for LES are the Reynolds number, width of the channel, height of the rib and sub-grid model parameters. For KS the parameters are the energy dissipation rate obtained from LES, the energy spectra, ratio of the largest and smallest sub-grid scales and the total number of modes for the sub-grid velocity field. The turbulent flow features thus obtained are compared with published experimental data [3] in a ribbed channel. Our results suggest that the particle deposition in the ribbed channel can be greatly affected by the small-scale (sub-grid) turbulent flow structures.