A SUBLAYER MODEL FOR TURBULENT DEPOSITION OF PARTICLES IN VERTICAL DUCTS WITH SMOOTH AND ROUGH SURFACES

The sublayer model for deposition of spherical particles from turbulent air streams in vertical ducts with smooth and rough walls is described. The formulation is based on the coherent vortical structure of near-wall turbulence and the detailed analysis of particle trajectories in this flow field. The Stokes drag, the Saffman lift force, and the gravitational force are included in the equations of particle motion. The wall roughness is taken into account by an appropriate modification of the boundary condition for the particle capture trajectories. The predicted deposition rates under various conditions are compared with the available experimental data and a reasonable agreement is observed. It is noticed that the particle-to-fluid density ratio, the shear-induced lift force, the wall roughness, the gravity direction and the flow Reynolds number have profound effects on the particle deposition rate. Based on a perturbation method, a simplified empirical equation for evaluating the turbulent deposition rate is also proposed.