0278-6826=01=$12.00 C.00 A Numerical Investigation of Particle Deposition on a Square Cylinder Placed in a Channel Flow

Particle deposition on a square cylinder placed in a rectangu-lar channel was investigated for unsteady vortical ows. For the two-phase ow simulations, the unsteady gas ow eld was com-puted by solving the incompressible Navier-Stokes equations using a staggered-grid control volume approach and the Marker-and-Cell (MAC) technique. The particle dynamics were simulated us-ing themodi edBasset-Bousinesq-Oseen(BBO) equation. The gas-phase 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 interme-diate 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