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 was investigated for unsteady vortical  ows. For the two-phase  ow simulations, the unsteady gas  ow Ž eld was computed by solving the incompressible Navier-Stokes equations using a staggered-grid control volume approach and the Marker-andCell (MAC) technique. The particle dynamics were simulated using themodiŽ edBasset-Bousinesq-Oseen(BBO) equation. The gasphase algorithm was validated using four test problems involving both steady and unsteady  ows. Numerical experiments were also conducted to evaluate the relative contributions of various terms in the BBO equation. For particle dynamics in unsteady vortical  ows, all the secondary termswere found to be negligible compared to the steady state viscous term at particle density ratios>20. The two-phase  ow model and the detailed  ow visualization were then employed to characterize particle dispersion and deposition as a function of the Reynolds number, particle Stokes number (St), and density ratio ("). Particledispersion in the cylinderwake exhibiteda typical nonmonotonic behavior. ParticleswithSt< 0.1 behaved like  uid particles, whereas those with St between 0.1 and 0.5 dispersed more than  uid particles and those with St > 1.0 were essentially unaffectedby the  ow in the nearwake region. Inaddition, the small St particles were distributed in the vortex core, while the intermediate St particleswere distributedaround the vortex periphery. For " > 20, the particle deposition was essentially characterized by the Stokes number. The amount of deposition increased precipitously 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 transitional regimes, the Reynolds number (Re) had a negligible effecton particle deposition, but amore discernible effect on particle distribution and dispersion.