Geoscience Reference
In-Depth Information
22.5 and 20 cm, respectively. The main channel section was trapezoidal, and
the branch channels were rectangular. The slope of the inclined bank was set at
1.5:1 (
m
1.5). The heights of both channels were chosen at 70 cm, and 10-cm thick
Plexiglas is used as the channel walls. The branch channel was set at a distance of
5.5 m from the entrance of the channel. To adjust the discharge as well as the water
depth in the channels, two sluice gates are installed at their ends. The water flow was
issued from an underground source. To assure the flow expansion as well as low
turbulence, a honeycomb was set up at the entrances of the main channel. The
discharges from the main and branch channels were measured by means of two
V-shaped weirs of 56
and 90
, respectively. The water depths in the upstream of the
main channel were 10, 20, and 25 cm, and the chosen Froude numbers for the
upstream of the main channel were 0.25, 0.30, 0.35, 0.40, and 0.45.
To perform any case of the experiment, first of all, the discharge of the main
channel for the corresponding depth and Froude number was calculated, then this
discharge was established in the main channel where both gates were completely
down (free state), and after the flow became steady, the diversion flow ratio was
measured using the V-shaped weirs. Afterward, the gates were brought up to the
extent that both the diversion flow ratio and the desired depth were safeguarded. At
the initial part of the main channel, there is a sediment injective source besides an
electromotor with variable revolution which makes it possible that with different
discharges, the sediment with the same concentration is injected. The applied
sediments are from colored crystal with
¼
1.05. At the end part of the main and
branch channels, there exists a basket to trap the sediments. In the experiments
concerning suspended sediments, using the electromotor with variable revolution,
the rate of the injected sediments in the main channel upstream was so adjusted that
in all the cases of the experiment the concentration would be the same and equal to
1gL
1
s
1
.
The sampling of the entered sediments in the branch channel was regularly
performed and measured by trapping, and after reaching the steady state the main
sampling has begun. Each sediment test took 90 min to be carried out. After the
termination of the experiments, the trapped sediments were gathered, dried, and
then weighed.
r ¼
3 Dimension Analysis
Using dimension analysis, the effective parameters in the phenomenon were per-
ceived, and the dimensionless ratios determined.
The parameters are the sediment discharge at the upstream of the main channel
(
Q
su
), the sediment discharge in the intake (
Q
si
), flow discharge at the upstream of
the main channel (
Q
u
), hydraulic depth at the upstream of the main channel (
D
u
),
duration of each experimental test (
t
), average diameter of sediments (
d
50
), water
density (
r
), sediment density (
r
s
), gravitational acceleration (
g
), bed roughness (
k
s
),
fluid viscosity (
n
), shear velocity (
u
*
), the intake angle (
y
), the stream tube width (
B
),
