De. Rosner et al., LOCAL SIZE DISTRIBUTIONS OF PARTICLES DEPOSITED BY INERTIAL IMPACTIONON A CYLINDRICAL TARGET IN DUST-LADEN STREAMS, Journal of aerosol science, 26(8), 1995, pp. 1257-1279
We exploit recent developments on impinging single particle capture la
ws and rational correlations for inertial impaction on a circular cyli
nder in high Reynolds number crossflow [Israel and Rosner (1983) Aeros
ol Sci. Technol. 2, 45-51; Wessel and Righi (1988) Aerosol Sci. Techno
l. 9, 26-60] to predict the local size distribution of particles depos
ited by impaction on a cylindrical target when the mainstream particle
suspension is ''log-normal''. Because of both the aerodynamics of sel
ective impingement, and the nature of the sticking/rebound law, we sho
w that the granular deposit particle size distribution (hereafter abbr
eviated (PSD)(W)) is generally quite different from mainstream particl
e size distribution (PSD)(infinity) by so much that (PSD)(W) generally
cannot be characterized accurately by single-mode log-normal distribu
tion parameters. Apart from its relevance in correcting for systematic
errors in aerosol sampling from high-speed streams, this local variat
ion of the ''granular deposit'' PSD along with information on deposit
morphology, must be known (in addition to the total mass accumulated p
er unit area) to predict, say, the loss in convective heat transfer ra
te associated with the growth of a fouling layer. Three distinct class
es of single solid particle capture laws are considered: constant capt
ure fraction (independent of impinging particle velocity and angle of
incidence), ''on-off'' capture behavior expected for impaction on a cl
ean, particle-free, smooth solid surface, and particle capture on a dr
y, sufficiently thick, granular deposit. Our (PSD)(W) results are cast
in terms of following accessible dimensionless parameters: sensitivit
y of capture fraction to particle incident velocity and angle, ratio o
f mainstream velocity to the critical (threshold) velocity for particl
e rebound (at, say, normal incidence), ratio of mean particle size in
the mainstream to the critical size required for impaction on a cylind
rical target in crossflow, spread of log-normal mainstream particle si
ze distribution, and the characteristic ''slip'' Reynolds number for t
he critical size particle in the mainstream.