A numerical investigation of particle deposition on a square cylinder placed in a channel flow

Particle deposition on a square cylinder placed in a rectangular channel wa s investigated for unsteady vortical hows. For the two-phase how simulation s, the unsteady gas how field was computed by solving the incompressible Na vier-Stokes equations using a staggered-grid control volume approach and th e Marker-and-Cell (MAC) technique. The particle dynamics were simulated usi ng the modified Basset-Bousinesq-Oseen (BBO) equation. The gasphase algorit hm was validated using four test problems involving both steady and unstead y flows. Numerical experiments mere also conducted to evaluate the relative contributions of various terms in the BBO equation. For particle dynamics in unsteady vortical flows, ail the secondary terms were found to be neglig ible compared to the steady state viscous term at particle density ratios > 20. The two-phase how model and the detailed flow visualization mere then e mployed to characterize particle dispersion and deposition as a function of the Reynolds number, particle Stokes number (St), and density ratio (epsil on). Particle dispersion in the cylinder wake exhibited a typical nonmonoto nic behavior Particles with St < 0.1 behaved like fluid particles, whereas those with St between 0.1 and 0.5 dispersed more than fluid particles and t hose with St > 1.0 mere essentially unaffected by the flow in the near wake region. In addition, the small St particles were distributed in the vortex core, while the intermediate St particles were distributed around the vort ex periphery. For epsilon > 20, the particle deposition was essentially cha racterized by the Stokes number. The amount of deposition increased precipi tously as St was increased from zero to unity then increased slowly for St between 1 to 3, and was essentially independent of St for St > 3.0. For the range of Reynolds numbers investigated, which included both laminar and tr ansitional regimes, the Reynolds number (Re) had a negligible effect on par ticle deposition, but a more discernible effect on particle distribution an d dispersion.