3 Hydrodynamics
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of the upstream reservoir and section 3-3 of the tail channel is established.
z +
α 1 V 2
1
2g
= H +
α 3 V 2
3
2g
+ h w1−2 + h w2−3
If we ignore the kinetic energy at sections 1-1 and 3-3, then
H = z − (h w1−2 + h w2−3 )
where z is the height difference between the reservoir water level and the tail
water level, and is called the reservoir head. h w1-2 is the head loss of the diversion tunnel from the reservoir to the surge well, and h w2-3 is the head loss of
the flow from the surge well to the pressure channel of the tailrace channel. H
is the hydraulic head of the turbine, which represents the mechanical energy
of the liquid per unit time and unit weight extracted by the hydraulic turbine
from the liquid flow. For the total discharge Q, the total mechanical power
(unit power) extracted by the turbine is
P w =
γ Q H
η
where η is the total efficiency of the turbine.
3.5 Steady Flow in Open Channel
3.5.1 Overview
Open channel is a kind of channel which is constructed manually or formed
naturally. When the liquid flows through these channels, it will form a free
surface contacting with the atmosphere. The pressure of each particle on the
surface is atmospheric pressure. This kind of flow with no pressure and free
surface is called open channel flow or no pressure flow. The flows in the water
conveyance channel (as shown in Figs. 3.24 and 3.25), aqueduct (as shown in
Fig. 3.26), culvert, and natural river channel are open channel flows. When
the hydraulic elements of open channel flow do not change with time, it is
called open channel steady flow; otherwise, it is open channel unsteady flow.
In the steady flow of open channel, if the streamline is a group of parallel
straight lines, the water depth, distribution of velocity, and the section average
velocity are constant along the flow direction, it is called the steady uniform
flow of open channel or the steady nonuniform flow. In the nonuniform flow
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of the upstream reservoir and section 3-3 of the tail channel is established.
z +
α 1 V 2
1
2g
= H +
α 3 V 2
3
2g
+ h w1−2 + h w2−3
If we ignore the kinetic energy at sections 1-1 and 3-3, then
H = z − (h w1−2 + h w2−3 )
where z is the height difference between the reservoir water level and the tail
water level, and is called the reservoir head. h w1-2 is the head loss of the diversion tunnel from the reservoir to the surge well, and h w2-3 is the head loss of
the flow from the surge well to the pressure channel of the tailrace channel. H
is the hydraulic head of the turbine, which represents the mechanical energy
of the liquid per unit time and unit weight extracted by the hydraulic turbine
from the liquid flow. For the total discharge Q, the total mechanical power
(unit power) extracted by the turbine is
P w =
γ Q H
η
where η is the total efficiency of the turbine.
3.5 Steady Flow in Open Channel
3.5.1 Overview
Open channel is a kind of channel which is constructed manually or formed
naturally. When the liquid flows through these channels, it will form a free
surface contacting with the atmosphere. The pressure of each particle on the
surface is atmospheric pressure. This kind of flow with no pressure and free
surface is called open channel flow or no pressure flow. The flows in the water
conveyance channel (as shown in Figs. 3.24 and 3.25), aqueduct (as shown in
Fig. 3.26), culvert, and natural river channel are open channel flows. When
the hydraulic elements of open channel flow do not change with time, it is
called open channel steady flow; otherwise, it is open channel unsteady flow.
In the steady flow of open channel, if the streamline is a group of parallel
straight lines, the water depth, distribution of velocity, and the section average
velocity are constant along the flow direction, it is called the steady uniform
flow of open channel or the steady nonuniform flow. In the nonuniform flow