Models for particle dispersion and flushing
Michael Dowd, Keith R. Thompson, and Jinyu Sheng
Assessing the near and far field effects of coastal mariculture
requires detailed knowledge of particle dispersion processes. We
present three case studies designed to illustrate the complexity of
this problem on spatial scales ranging from an inlet to the
continental shelf. The focus is on particle trajectories calculated
from Eulerian flow fields obtained from numerical models. The first
case deals with a tidally flushed coastal inlet (Upper South Cove,
located near Lunenburg, N.S., Canada). The complex geometry and strong
advective nonlinearities result in a marked flood/ebb tide asymmetry
and complex particle paths. Second, we present an idealized study of
periodic flow over isolated topography. In spite of the fact the flow
field is governed by essentially two parameters (the tidal excursion
and the forcing frequency), no simplified description of dispersion
seems possible. In the final case, particle dispersion and retention
indices are shown for the Scotian Shelf. In all three cases particle
trajectories are complex and not amenable to simple parameterization
schemes. We suggest instead that a statistical or probabilistic
description of particle dispersion and flushing should be derived from
existing circulation models. These reduced dimension models are then
able to be effectively utilized in modelling the environmental effects
of mariculture.