JNTU
JNTU B.Tech II FLUID MECHANICS AND HYDRAULIC MACHINERY Previous Question Paper (November/December - 2018 - R13)
Note: This question paper contains two parts A and B. 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. Each question carries 10 marks and may have a, b, c as sub questions.
Part A
Define pressure. Obtain an expression for the pressure intensity at a point in a fluid.
Answer
Pressure is defined as the normal force exerted by a fluid per unit area. The intensity of pressure at a point in a static fluid is given by the expression p = ρgh, where ρ is the fluid density, g is the acceleration due to gravity, and h is the depth of the point below the free surface.
Derive an expression for the force exerted on a sub-merged vertical plane surface by the static liquid and locate the position of centre of pressure.
Answer
The total force F on a vertical plane surface is F = ρgA h̄, where A is the area of the surface and h̄ is the depth of the centroid. The centre of pressure h* is located at h* = h̄ + (IG sin2θ) / (A h̄), where IG is the moment of inertia about the centroidal axis and θ = 90° for a vertical plane.
What is Euler’s equation of motion? How will you obtain Bernoulli’s equation from it?
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What do you understand about major energy loss and minor energy losses in pipes?
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What is meant by pumped storage plant.
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What is flow mass curve? How is it constructed?
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How will you classify the turbines?
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What is meant by the speed ratio of a pelton wheel?
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Define what is NPSH?
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Explain the role of model analysis in Hydraulic machines.
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Part B
Develop the expression for the relation between gauge pressure P inside a droplet of liquid and the surface tension.
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Explain Newtonian and Non-Newtonian fluids, vapor pressure, and compressibility.
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Differentiate between:
- Stream function and velocity potential function
- Stream line and streak line
- Rotational and irrotational flows.
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A 300 mm diameter pipe carries water under a head of 20 m with a velocity of 3.5 m/s. If the axis of the pipe turns through 45 degrees, find the magnitude and direction of the resultant force at the bend.
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Three reservoirs A, B and C are connected by a pipe system having length 700 m, 1200 m and 500 m and diameters 400 mm, 300 mm and 200 mm respectively. The water levels in reservoirs A and B from a datum line are 50 m and 45 m respectively. The level of water in reservoir C is below the level of water in reservoir B. Find the discharge into or from the reservoirs B and C if the rate of flow from reservoir A is 150 litres per sec. Find the height of water level in the reservoir C. Take f = 0.005 for all the pipes.
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A jet of water having a velocity of 20 m/s strikes a curved vane, which is moving with a velocity of 10 m/s. The jet makes an angle of 20 degrees with the direction of motion of vane at inlet and leaves at an angle of 130 degrees to the direction of motion of vane at outlet. Calculate:
- Vane angles, so that the water enters and leaves the vane without shock.
- Work done per second per unit weight of water striking the vane per second.
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Prove that the work done per second on a series of moving curved vanes by a jet of water striking at one of the tips of a vane is given by (with usual notation), Work done /sec = ρaV1 [Vw1 ± Vw2] × u.
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233 liters of water per second are supplied to an inward flow reaction turbine. The head available is 11 m. The wheel vanes are radial and inlet diameter is twice the outlet diameter. The velocity of flow is constant and equal to 1.83 m/s. The wheel makes 370 r.p.m Find:
- Guide vane angle
- Inlet and outlet diameter of the wheel
- The width of the wheel at inlet and exit.
Neglect the thickness of the vanes. Assume that the discharge is radial and there are no losses in the wheel. Take speed ratio = 0.7.
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Write short note on:
- Draft tube theory
- Surge tank
- Model study of Turbines.
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Discuss the classification of pumps.
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A centrifugal pump rotating at 1000 r.p.m. delivers 160 litres/s of water against a head of 30 m. The pump is installed at a place where atmospheric pressure is 1 x 10^5 Pa (abs.) and vapor pressure of water is 3 kPa (abs.). The head loss in suction pipe is equivalent to 0.2 m of water. Calculate:
- Minimum NPSH
- Maximum allowable height of the pump from free surface of water in the sump.
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Draw and discuss the operating characteristics of a centrifugal pump.
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Briefly state the significance of similarity parameters in hydraulic pumps.
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