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JNTU B.Tech II MECHANICS OF FLUIDS AND HYDRAULIC MACHINES Previous Question Paper (March/April - 2021 - R15)

B.Tech | II | II-II | R15 | March/April - 2021

Answer PaperPaper Code: 124DF/114DFMaximum Marks: 75Time: 3 hours

Answer any Five Questions

All Questions Carry Equal Marks

Main

115 marks
a

What is the pressure corresponding to 30 cm column of Kerosene of relative density 0.85? What is the equivalent head of mercury corresponding to this pressure?

5 marks

Answer

Given the height of the kerosene column h = 0.3 m and the relative density S = 0.85, the density of kerosene is ρ = 0.85 × 1000 = 850 kg/m3. The pressure P is calculated as:

P = ρ × g × h = 850 × 9.81 × 0.3 = 2501.55 N/m2

To find the equivalent head of mercury (hHg), we equate the pressure to that of a mercury column, where the density of mercury ρHg = 13600 kg/m3:

hHg = P / (ρHg × g) = 2501.55 / (13600 × 9.81) ≈ 0.01875 m = 1.875 cm
b

A sleeve 20 cm long encases a vertical metal rod 5 cm in diameter with a radial clearance of 0.02 mm. If when immersed in an oil of viscosity 8 poise, the weight of the sleeve is 10 N, will the sleeve slide down the rod and if so at what velocity?

10 marks

Answer

The sleeve will slide down if the weight of the sleeve (W = 10 N) exceeds the viscous drag force (F) acting on it. The viscous force is given by Newton's law of viscosity:

F = μ × A × (du / dy) = μ × (π × D × L) × (v / t)

Where:

  • μ = 8 poise = 0.8 Ns/m2
  • D = 0.05 m
  • L = 0.2 m
  • t = 0.02 mm = 0.00002 m
  • A = π × 0.05 × 0.2 = 0.031416 m2

The force required to hold the sleeve in equilibrium is F = 10 N. Setting F = 10 and solving for velocity v:

10 = 0.8 × 0.031416 × (v / 0.00002)
v = (10 × 0.00002) / (0.8 × 0.031416) ≈ 0.00796 m/s

Since the weight of the sleeve is 10 N, it will overcome the viscous resistance and slide down the rod at a terminal velocity of 0.00796 m/s.

215 marks
a

The pressure outside the droplet of water of diameter 0.03 mm is 9.5 N/cm2 (atmospheric pressure). Calculate the pressure within the droplet if surface tension is given as 0.0685 N/m of water.

6 marks

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b

Define Viscosity. A plate having an area of 0.7 m2 is sliding down the inclined plane at 45° to the horizontal with a velocity of 0.45 m/s. There is a cushion of fluid 2 mm thick between the plane and the plate. Find the viscosity of the fluid if the weight of the plate is 300 N.

9 marks

Answer

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315 marks
a

Differentiate (i) uniform and non-uniform flow (ii) rotational and irrotational flow with suitable examples.

6 marks

Answer

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b

A jet of water from a 15mm diameter nozzle is directed vertically upwards. Assuming that the jet remains circular and neglecting any loss of energy, what will be the diameter at a point 3.5 m above the nozzle, if the velocity with which the jet leaves the nozzle is 15 m/s.

9 marks

Answer

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415 marks
a

A bend in pipe line carrying water gradually reduces from 0.5 m to 0.2 m diameter and deflects the flow through angle of 60°. At the larger end the gauge pressure is 180 kN/m2. Determine the magnitude of the force exerted on the bend when there is no flow in the pipe.

10 marks

Answer

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b

Differentiate continuity equation for 1-D and 3-D flows.

5 marks

Answer

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515 marks
a

A pipe 8 cm in diameter, 500m long and with f=0.018 is connected in parallel between two points M and N with another pipe 5 cm diameter, 1000 m long and having f=0.020. A total discharge of 40 lit/s enters the parallel pipes through division at M to rejoin at N. Estimate the division of discharge in the two pipes.

9 marks

Answer

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b

Explain about Displacement thickness and energy thickness of boundary layer.

6 marks

Answer

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615 marks
a

Air flows at 15 m/s past a smooth rectangular flat plate 0.2 m wide and 3 m long. Assuming that the turbulence level in the oncoming stream is low and that transition occurs at Re=5×105, calculate drag force due to laminar and turbulent boundary layer.

10 marks

Answer

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b

Differentiate total energy line and hydraulic gradient line.

5 marks

Answer

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715 marks
a

Derive the work done/sec when jet striking at series of radial curved vanes.

10 marks

Answer

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b

Differentiate impulse turbines and reaction turbines.

5 marks

Answer

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815 marks
a

Describe about discharge slips in reciprocating pumps.

5 marks

Answer

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b

A centrifugal pump of the radial type delivers 5000 lit/minute against a total head of 38m, when running at a speed of 1450 rpm. If the outer diameter of the runner is 300 mm and its width at the outer periphery is 13mm, find the vane angle at exit. Assume manometric efficiency is 80%.

10 marks

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This page contains the solved question paper with answers of MECHANICS OF FLUIDS AND HYDRAULIC MACHINES from JNTU for B.Tech ME II II-II, March/April - 2021, R15.

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