Environmental Engineering Reference
In-Depth Information
3 Results
3.1 Channel Width of 2.5 Centimeters
The experiments were conducted to detect the accumulation of particles after thou-
sand of periods. For this case, the channel width is 2.5 cm and the driving frequency is
0.08Hz. The experiment lasted for 15h, which corresponds approximately to 4,000
periods. In a tidally induced flow 4,000 periods are approximately 6 years. Accord-
ingtoEqs.
3
and
4
the values of maximal flow rate and the representative velocity
are respectively:
Q
0
=
10
−
4
m
3
/s and
U
3
.
47
×
=
0
.
3468m/s. So the flow has a
Reynolds number
Re
0.006.
In Fig.
2
we present a snapshot of the final distribution of particles. In this figure
we see how the flow lifts the particles and moves them away from their original
positions. As we stated, we start with particles uniformly distributed on the bottom.
After several periods, a fraction of the particles have been completely removed from
their initial position in the channel and near the channel outlet. After thousands of
periods the particles initially located in front of the channel have been removed. The
region for which particles are expelled extends a little more than 20 cm (8H) along
the axis of symmetry and has a width of approximately 8 cm (3.2H).
Under these conditions the particle distribution remains symmetric. Particles
concentrate inside the channel and a trough is formed in front of it, in the open domain.
This last structure has been observed in coastal system by Amoroso and Gagliardini
(
2010
). The concentration of particles inside the channel has been reported in a
numerical simulation but only over 15 periods (López-Sánchez and Ruiz-Chavarría
2013a
).
=
8,700 and a Strouhal number
S
=
Fig. 2
Distribution of sand
in the system after 15h of
forcing. The channel width is
2.5 cm and the driving period
is 12.5 s. Particles
concentrate inside the
channel and a trough appears
in front of the channel
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