JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II HYDRAULICS AND HYDRAULIC MACHINERY Previous Question Paper (May - 2019 - R13)
Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit.
Part A
List the applications of Hydraulic Jump.
Answer
The hydraulic jump is primarily used in hydraulic engineering for the following purposes:
- To dissipate excess kinetic energy of water flowing over spillways, sluice gates, or weirs, thereby preventing downstream erosion and scouring of the riverbed.
- To act as an energy dissipator to stabilize the flow conditions in open channels.
- To increase the depth of flow downstream to facilitate water measurement or to maintain a required water level for irrigation or diversion structures.
- To facilitate the mixing of chemicals in water treatment processes by creating high turbulence.
Differentiate critical, sub critical and super critical flow in a open channel.
Answer
The classification of flow in an open channel is determined by the Froude number (Fr), which is defined as the ratio of inertial forces to gravitational forces, given by the formula:
where v is the mean velocity, g is the acceleration due to gravity, and D is the hydraulic depth. The flow regimes are differentiated as follows:
- Sub-critical flow (Fr < 1): The flow velocity is less than the wave celerity. Disturbances created in the flow can travel upstream, and the flow is characterized by high depth and low velocity.
- Critical flow (Fr = 1): The flow velocity is exactly equal to the wave celerity. This state represents the condition of minimum specific energy for a given discharge.
- Super-critical flow (Fr > 1): The flow velocity is greater than the wave celerity. Disturbances cannot travel upstream, and the flow is characterized by low depth and high velocity.
What are the different types of similarities?
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Distinguish the term model and prototype quoting with examples.
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Define and explain the term impact of jet.
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What is angular momentum principle? How it is useful in impact of jets?
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Write the classification of hydraulic turbine.
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Compare operating characteristics of impulse turbine with reaction turbine.
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What is utilization factor? How it is used in hydraulic power plants.
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Why cavitation occurs in C.P? Explain how it can be controlled.
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Part B
An open channel 3 m wide rectangular in shape carries the discharge at normal depth of 1.2 m. What should be the slope of channel if the Manning’s “n” is 0.014.
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A wide rectangular channel carries a flow of 2.75 m3/s per meter width, the depth of flow being 1.5 m. Calculate the rise of the floor level required to produce critical flow conditions. What is the corresponding fall in surface level?
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Determine approximate water surface slope (m per km) at a point in a rectangular channel in which the discharge is 0.84 m3/s, the bed width is 3 m, the depth of flow is 0.75 m and the bed slope is 0.15 m per km. Assume C in Chezy’s formula as 55 and take energy coefficient alpha equal to unity.
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What do you mean by dimensionally homogenous equation? Give few examples.
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What is meant by hydraulic similarity between a model and prototype?
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What is kinematic similarity? What is its significance?
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A turbine develops 1900 KW at 500 rpm under a net head of 22 m. Its diameter is 2.5m. A model of 1:5 is tested under a head of 4 m. Estimate the size, speed, discharge and power developed by the model. Assume an efficiency of 82%.
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Show that the force exerted by a jet of water on an inclined fixed plate in the direction of the jet is given by
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A jet of water of diameter 50mm moving with a velocity of 20m/sec strikes a fixed plate in such a way that the angle between the jet and the plate is 60°. Find the force exerted by the jet on the plate i) In the direction normal to the plate ii) In the direction of the jet.
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A water jet 20 mm in diameter and having a velocity of 90 m/s strikes series of moving blades in a wheel. The direction of the jet makes 20° with the direction of movement of the blade. The blade angle at inlet is 35°. If the jet should enter the blade without striking, what should be the blade velocity? If the outlet angle of the blade is 30°, determine the force on the blade. Assume that there is no friction involved in the flow over the blade.
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A Pelton wheel has to be designed for the following data: Power to be developed = 6000 kW. Net head available = 300 m; Speed = 550 r.p.m; Ratio of jet diameter to wheel diameter = 1/10; and overall efficiency = 85%. Find the number of jets; diameter of the jet; diameter of the wheel; and the quantity of water required.
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A pelton wheel develops 4500 kW under a net head of 125 m while running at a speed of 200 rpm. Assuming Kv = 0.98, speed ratio Ku = 0.46 and overall efficiency η0=88%, the ratio of nozzle diameter to pitch circle diameter (d/D) = 1/9. Determine: (a) discharge required (b) diameter of wheel (c) the diameter and number of jets required.
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Explain the significance of similarity parameters in centrifugal pump.
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A centrifugal pump with radial inflow delivers 0.06 m3/s of water against a total head of 35 m. If the outer diameter of the impeller is 40 cm and its width at the outer periphery is 1.3 cm, find the blade angle at exit. The speed of the pump is 1200 rpm and its efficiency is 75%.
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The diameter and width of a centrifugal pump impeller are 50 cm and 2.5 cm. The pump runs at 1200 rpm. The suction head is 6 m and the delivery head is 40 m. The frictional drop in suction is 2 m and in the delivery 8 m. The blade angle at outlet is 30°. The manometric efficiency is 80% and the overall efficiency is 75%. Determine the power required to drive the pump. Also calculate the pressures at the suction and delivery side of the pump.
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