The evolution of a mono-disperse gravity current in the lock-exchange configuration
is investigated by means of direct numerical simulations for various Reynolds
numbers and settling velocities for the deposition. We limit our investigations to
gravity currents over a flat bed in which density differences are small enough for the
Boussinesq approximation to be valid. The concentration of particles is described in
an Eulerian fashion by using a transport equation combined with the incompressible
Navier-Stokes equations. The most interesting results can be summarized as
follows: (i) the settling velocity is affecting the streamwise vortices at the head of
the current with a substantial reduction of their size when the settling velocity is
increased; (ii) when the Reynolds number is increased the lobe-and-cleft structures
are merging more frequently and earlier in time, suggesting a strong Reynolds
number dependence for the spatio-temporal evolution of the head of the current;
(iii) the temporal imprint of the lobe-and-cleft structures can be recovered from
the deposition map, suggesting that the deposition pattern is defined purely and
exclusively by the structures at the front of the current.