lerosol Science, 1975, Vol. 6, pp. 31 to 43. Pergamon Press. Printed in Great Britain. IMPINGEMENT OF SPHERICAL PARTICLES ON ELLIPTICAL CYLINDERS JACOB H. MASLIYAH and ALFRED DUFF Department of Chemistry and Chemical Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, Canada (First received 18 December 1973; and in revised.form 20 May 1974) Abstract -Symmetric laminar flow past elliptical cylinders was obtained by the numerical solution of the Navier-Stokes equations for Reynolds numbers up to 40, based on the axis of the elliptical cylinder perpendicular to the main flow direction. The trajectories of spherical particles in the flow field were traced and the impaction efficiencies were evaluated for a particle Stokes number range of 0.3-200 and for various spherical particle sizes. Comparison with potential flow around the ellip- tical cylinders was made. The ratio of the minor to the major axis of the elliptical cylinders was 0.2. NOMENCLATURE b semi-axis of the elliptical cylinder perpendicular to the flow direction CD drag coefficient c focal length of the elliptical coordinate system Dp spherical particle dia. E collision or impaction efficiency i ~-1 K ratio of the spherical particle dia. to the axis of the elliptical cylinder perpendicular to the flow direction mp buoyancy mass of spherical particle P inertial particle parameter Rc Reynolds number of the elliptical cylinder Rp Reynolds number of the spherical particle t dimensionless time ( = t' U/b) U free stream velocity v s dimensionless fluid velocity vector (= v'y/U) vp spherical particle dimensionless velocity vector (= vi, U) v~ dimensionless fluid velocity in the r/direction (= v'~/U) v¢ dimensionless fluid velocity in the ¢ direction (= v'/U) x, y dimensionless cartesian coordinates (= x'/b. y'/b) Z dimensionless complex number ( = Z'/b) Greek letters q V P q, Subscripts a c f i P x Y dimensionless vorticity elliptical coordinates, angle kinematic viscosity elliptical coordinates, radial density dimensionless stream function cylindrical surface critical yalue pertains to fluid starting value pertains to particle x-direction y-direction 31