JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II FLUID MECHANICS AND HYDRAULIC MACHINERY Previous Question Paper (August/September -2022 - R13)
Answer any five questions. All questions carry equal marks.
Main
A plate 2.5 × 10-5 m distant from a fixed plate moves at 0.60 m/s and requires a force of 1.96 N/m2 to maintain this speed. Determine the fluid viscosity of the substance that fills the space between the plates.
Answer
According to Newton's law of viscosity, the shear stress τ is proportional to the velocity gradient du/dy. The relationship is given by:
Where:
- τ = 1.96 N/m2 (shear stress)
- du = 0.60 m/s (change in velocity)
- dy = 2.5 × 10-5 m (distance between plates)
- μ = dynamic viscosity
Rearranging the formula to solve for μ:
Substituting the given values:
Calculate pressure gauge reading for the case shown in figure.
Answer
To calculate the pressure gauge reading, we apply the principle of hydrostatic equilibrium, where the pressure at any horizontal level in a continuous static fluid is equal. Starting from the free surface or the known pressure point, the pressure at any depth h is given by:
For a multi-fluid system, the pressure at the gauge is determined by summing the hydrostatic heads of the fluid columns:
Where ρi is the density of each fluid, g is the acceleration due to gravity (9.81 m/s2), and hi is the vertical height of each column. If the system involves an open end, the pressure is calculated relative to atmospheric pressure. By traversing from the open end to the gauge, add pressure for downward movements and subtract for upward movements to find the final gauge reading.
A cylinder contains a fluid at a gauge pressure of 350 kN m–2. Express this pressure in terms of a head of (i) water (ρH2O = 1000 kg m–3), (ii) mercury (relative density 13.6). What would be the absolute pressure in the cylinder, if the atmospheric pressure is 101.3 kN m–2.
Answer
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The space between two parallel plates 1.5 cm apart is filled with an oil of viscosity μ = 0.050 kg/m s. A thin 30 × 60 cm rectangular plate is pulled through the oil 0.50 cm from one plate and 1.00 cm from the other. What force is needed to pull the plate at 0.40 m/s.
Answer
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The flow of a fluid has velocity components u = 3x+y, v = 2x – 3y. Determine whether the flow is irrotational.
Answer
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Two pipes of diameter 40 cm and 20 cm are each 300 m long. When the pipes are connected in series and discharge through pipe line is 0.10 m3/s. Find the loss of head incurred. What would be the loss of head in the system to pass the same total discharge when the pipes are connected in parallel? Take f = 0.0075 for each pipe.
Answer
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Define:
- piezometric head
- Total energy line and
- Hydraulic gradient line.
Answer
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Write short notes on the following: i) Firm Power ii) Secondary power iii) Utilization factor iv) Load duration curve.
Answer
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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 600. Find the force exerted by the jet on the plate.
- In the direction normal to the plate
- In the direction of the jet.
Answer
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Derive equations for the force of impact of a fluid jet on a series of normal flat vanes mounted on a wheel. The vane velocity is less than jet velocity. In this case, prove that the maximum possible hydraulic efficiency is 50%.
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A jet of water of diameter 5 cm and velocity 20 m/s impinges on (i) a normal flat vane moving in the direction of jet at 7.6 m/s and (ii) a series of normal flat vanes mounted on a wheel which has a tangential velocity of 7.5 m/s. Calculate force exerted, work done by water and efficiency of the system in both cases.
Answer
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Define specific speed of a hydraulic turbine. Derive an equation for specific speed in terms of operating speed, power and heads.
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Explain the factors involved in selection of a hydraulic turbine.
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Derive the formula for the head developed by a centrifugal pump.
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A centrifugal pump with radial inflow delivers 0.06 cumecs 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%.
Answer
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