Article,
Mechanisms for Microparticle Dispersion in a Jet in Crossflow
AIChE Journal, 51 (1): 28--43 (January 2005)
DOI: 10.1002/aic.10301
Abstract
The dispersion produced by a jet injecting microparticles in a cross stream is controlled by
the interaction between dispersed species and large-scale time-dependent flow structures
populating the transverse jet. These structures span over a wide range of spatial and temporal
scales and are not equally effective in advecting and dispersing species. In many environ-
mental and industrial applications, the species advected by the jet stream are expected to
undergo rapid and homogeneous dilution away from the injection point. Preferential accu-
mulation of particles into specific flow regions may have consequences on the overall
industrial process. For instance, nonuniform particle distribution can severely downgrade the
efficiency of postcombustion devices. In this work, we address the problem of identifying which
of the flow structures in a jet in crossflow controls dispersion mechanisms of inertial particles,
focusing specifically on the issue of their preferential distribution. The flow field produced by
the transverse jet is calculated using a finite-volume solver of Navier–Stokes equations and the
dispersion of particles is computed using a Lagrangian approach. We investigate the behavior
of particles of different sizes, examining 5 orders of magnitude of their inertial parameter—the
particle timescale. The analysis of dispersion shows that particle distribution is not uniform
and is dominated by specific flow structures. Examining the distribution of the different
particles in connection with particle timescale and flow structure evolution, it is found that
shear layer vortices initially control dispersion and segregation processes, whereas counter-
rotating vortices entrain and trap particles in the lee side of the jet.
