The turbulent boundary layer above and within a corn canopy
is dominated by a succession of sweep and ejection events, the
former being a fast downward flow and the latter a slow
upward flow (see e.g. Shaw et al., 1983). These events are the
primary mechanisms for momentum and scalar exchange
with the atmospheric boundary layer above the canopy. In
addition, it has been shown by direct numerical simulations
(DNS, e.g. Soldati, 2005) that the ejection-sweep cycles are
instrumental in the entrainment, dispersal and deposition of
heavy particles. Ejection-sweep cycles in corn canopy flows
have been investigated by Shaw et al. (1983) and by Zhu et al.