JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II Year HYDRAULICS AND HYDRAULIC MACHINERY Previous Question Paper (July/August - 2021 - R15)
Answer any Five Questions. All Questions Carry Equal Marks.
Main
The discharge of water through a rectangular channel of width 8 m, is 15 m3/s when depth of flow of water is 1.2 m. Calculate Critical depth, critical velocity and value of minimum specific energy.
Answer
Given: Width (B) = 8 m, Discharge (Q) = 15 m3/s, Depth (y) = 1.2 m.
Discharge per unit width (q) = Q / B = 15 / 8 = 1.875 m2/s.
1. Critical depth (yc):
2. Critical velocity (Vc):
3. Minimum specific energy (Emin):
Explain the energy variation in a short hydraulic jump using specific energy equation.
Answer
A hydraulic jump represents a transition from supercritical flow to subcritical flow, characterized by a sudden rise in water level. In the specific energy diagram, the flow moves from a state of low depth and high energy (supercritical) to a state of high depth and lower energy (subcritical) for the same discharge.
The energy loss (ΔE) in the jump is the difference between the specific energies before and after the jump:
Key points of energy variation:
- The flow is highly turbulent, causing significant dissipation of kinetic energy into heat.
- The specific energy equation shows that while discharge remains constant, the jump is dissipative, meaning the specific energy at the downstream section (E2) is always less than the specific energy at the upstream section (E1).
- The jump occurs because the flow cannot transition smoothly from supercritical to subcritical without this energy-consuming turbulence.
What do you understand by (i) steady and Unsteady flow; (ii) uniform and non uniform flow in case of open channels.
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State the conditions under which the rectangular section of an open channel will be most economical. Derive these conditions.
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What do you mean by repeating variables? How are repeating variables selected in dimensional analysis?
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Explain different types of hydraulic similarities that exist between prototype and its model.
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What do you mean by dimensionless numbers? Explain any four dimensionless numbers.
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The discharge through a weir is 1.5 m3/s. Find the discharge through the model of the weir if the horizontal dimension of the model = 1/50 the horizontal dimension of the prototype and the vertical dimension of the model = 1/10 the vertical dimension of the prototype.
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A jet of water of diameter 7.5 cm strikes a curved plate at its centre with a velocity of 20 m/s. The curved plate is moving with a velocity of 8 m/s in the direction of the jet. The jet is deflected through an angle of 165°. Assuming the plate to be smooth find: (i) Force exerted on the plate in the direction of jet (ii) power of the jet and (iii) Efficiency of the jet.
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A reaction turbine works under a head of 115 m and its speed is 450 rpm. The diameter of the inlet is 1.2 m and the flow area is 0.4 m2. At the inlet, the absolute and the relative velocities make angles of 20° and 60° respectively with the tangential velocity. Determine the power developed and the hydraulic efficiency. Assume the velocity of the whirl at the outlet as zero.
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Derive the expressions for work done and efficiency when a jet striking centrally on an inclined vanes.
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What do you understand by the characteristics curve of a turbine? Name and explain the important types of characteristic curves.
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What do you mean by gross head, net head and efficiency of a turbine? Explain the different types of efficiencies of a turbine.
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What is the difference between single stage and multistage pumps? Describe multiple stage pump with impellers in parallel.
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List and explain the different classification of Hydropower plants.
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