Match the English and Russian equivalents.

 

1) conduit intake	a) водоприёмник насосной станции
2) dry-tower intake	b) водоприёмник ГЭС
3) free water intake	c) открытый водозабор
4) gravity intake	d) глубинный водоприёмник
5) high-pressure intake	e)высоконапорный (глубинный) водоприёмник
6) integral intake	f) боковой водозабор
7) lateral-water intake	g) самотёчный водозабор
8) low-level intake	h) водозабор открытого типа
9) low-pressure intake	i) высокий башенный водоприёмник
10) power intake	j) водоприёмник водовода
11) pumping-plant intake	k) низкий башенный водоприёмник
12) river (stream) intake	l) водозабор закрытого типа
13) screen (trash-racked) intake	m) башенный водоприёмник
14) siphon intake	n) речной водозабор; русловой водозабор
15) tower intake	o) сифонный водоприёмник
16) undersurrace water intake	p) водоприёмник с сороудерживающей решёткой
17) wet-tower intake	q) 1) водозабор, совмещённый со зданием ГЭС; 2) водозабор многоцелевого назначения

Reading Task

 

Find the translation of the following terms and memorize their meaning.

conduit	a trash rack	conjugate
steel bars	a shaft	debris
withdrawal	friction	a shell
a withdrawal conduit	high-head	to dissipate
a power-driven rack	elaborate	intake shaft
tailwater elevation	to draw	head of water
tractor gates	tube valve	clogging
cylinder gate	jump	fluctuation
slide gates	crib	to interfere with
butterfly valve	tower intake	scour
needle valve	a submerged intake	a port
intake valve	sediment	supercritical
subcritical	to aid
high-head regulating valve

 

Read the text to get the gist of it. Answer the following questions.

a) What is the primary function of an intake structure?

b) Where are intake towers often used?

 

Text Intakes

An intake structure is required at the entrance to a conduit through which water is withdrawn from a river or reservoir. Intake structures vary from a simple concrete block supporting the end of a pipe to elaborate concrete intake towers, depending upon reservoir characteristics, climatic conditions and other factors. The primary function of the intake structure is to permit withdrawal of water from the reservoir and to protect the conduit from damage or clogging.

Intake towers are often used where there is a wide fluctuation of water level. Ordinarily they are provided with ports located at various levels. They may aid flow regulation and permit some selection of the quality of water to be withdrawn. It is necessary to place the lowest ports far enough above the bottom of the reservoir so that sediment will not be drawn into them. A wet intake tower consists of a concrete shell filled with water to the level of the reservoir and has a vertical shaft inside connected to the withdrawal conduit. Gates are normally provided on the inside shaft to regulate flow.

A dry intake tower has no water inside of it since the entry ports are connected directly to the withdrawal conduit. Each entry port is provided with a gate or valve. An advantage of the dry tower is that water can be withdrawn from any selected level of' the reservoir. Intake towers should be located so as not to interfere with navigation and must be designed to withstand hydrostatic pressures and forces from earthquakes, wind, waves and ice.

A submerged intake consists of a rock-filled crib or a concrete block which supports the end of the withdrawal conduit. Because of their low cost, submerged intakes are widely used on small projects.

The entrance to intakes and sluiceways should be provided with trash racks. These racks are usually made of steel bars spaced on 2 to 6 inches depending on maximum size of debris which can be present in the conduit. Sometimes the rack is constructed in the form of a half cylinder. Debris which accumulates on the rack is sometimes removed by hand when necessary, but where much debris is expected automatic power-driven rakes are preferable.

Most intakes and sluiceways are provided with some type of gate or valve at their entrance, for example, high-head tractor gates, cylinder gates which can be used to close the flow into large intake towers of the wet types; interior gate valves which are located downstream from the conduit entrance. For smaller heads interior gate valves are often used to regulate flow but for greater heads they are ordinarily used only in the fully open or fully closed position. A butterfly valve is best suited for moderate heads, although they have been used under high heads; high head regulating valves: slide gates are not suitable for flow regulation under high heads. On high-heads installations needle valves and tube valves are widely used for flow regulation. They are usually placed at the downstream end of sluiceways and discharge directly into the atmosphere.

Water flowing over a spillway or through a sluiceway is capable of causing severe erosion of the stream bed and its banks below the dam. Whenever flow changes from supercritical to subcritical, a hydraulic jump will occur. The problem facing the designer is to find the location of the hydraulic jump under various conditions of flow. In order that a hydraulic jump may occur, the flow must be below critical depth. The location and character of the jump depend on tailwater elevation. For the jump to form at the toe of the dam, the tailwater elevation must coincide with the upper conjugate depth. If the tailwater depth is greater than conjugate depth, the overflowing water will underrun the tailwater without a jump.

If the tailwater depth is less than conjugate depth, flow will continue below critical depth for some distance downstream from the toe of the dam. Because of the energy loss to friction, the depth of flow will gradually increase until a new depth is reached which is conjugated with the tailwater depth.

The measures necessary to control erosion and dissipate the energy of the spillway flow are dependent on the relation between the upper conjugate depth and tailwater depth.

 

Comprehension Check