Environmental Engineering Reference
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results are in good accordance for velocities
1.5m/s. A pressure difference incre-
ment generate a velocity increment according to Eq. (
2
). The pressure difference
oscillations at low velocities are produced by the initial water height.
To verify the Venturi effect in the simulation, velocities and pressures where
calculated in five points across the Venturi tube (Fig.
7
). Each point is separated by
17mm. Figure
8
shows how the velocity and pressure change with time at the points
of Fig.
7
. The obtained results are in accordance with the Venturi effect, given that, a
reduction in the transversal area produce a velocity increase and a pressure decrease.
Pressure oscillations are observed at the beginning of the simulation by the water
initial conditions.
From the numerical results, the discharge coefficient variation as a function of the
Reynolds number in the throat was calculated (Fig.
9
). Similar results were obtained
by Mott (
2006
).
Fig. 7
Points in the Venturi tube where velocities and pressures are calculated
(a)
(b)
4.0
6.5
Point 1
Point 2
Point 3
Point 4
Point 5
6.0
3.5
5.5
5.0
3.0
4.5
2.5
4.0
3.5
2.0
3.0
2.5
1.5
2.0
Point 1
Point 2
Point 3
Point 4
Point 5
1.0
1.5
1.0
0.5
0.5
0.0
0.0
0.00
0.25
0.50
0.75
1.00
1.25
1.50
0.00
0.25
0.50
0.75
1.00
1.25
1.50
Time (seconds)
Time (seconds)
Fig. 8
Numerical results:
a
Velocity as a function of time,
b
pressure as a function of time.
Points
1, 2, 3, 4, and 5 are indicated in Fig.
7
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