POKHARA UNIVERSITY
Level: Bachelor
Programme: BE
Course: Fluid Mechanics
Semester – Spring
Year
: 2010
Full Marks: 100
Pass Marks: 45
Time
: 3hrs.
Candidates are required to give their answers in their own words as far
as practicable.
The figures in the margin indicate full marks.
Attempt all the questions.
1. a)
Explain the effect of temperature on viscosity of fluid. Derive an
expression for Newton's law of viscosity.
7
b)
Define the absolute, gauge and atmospheric pressure with appropriate
diagram. Find the expression for pressure height relationship.
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2. a)
Define total pressure and centre of pressure. Prove that the centre of
pressure always lies below the centre of gravity for completely
submerged surface.
8
b)
A wooden cylinder (sp.gr. = 0.54) of diameter 'd' and lenght 'l' is
required to float in oil (sp.gr. = 0.8). Find the l/d ratio for the cylinder
to float with its longitudinal axis vertical.
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Derive the continuity equation in Cartesian co-ordinates.
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b)
Find the density of a metallic body which floats at the interface of
mercury of specific gravity 13.6 and water such that 35 percent of its
volume is submerged in mercury and 65% in water.
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4. a)
What are the energies involved in the flowing fluid. Derive
Bernoulli's equation for an ideal liquid.
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b)
Derive an expression for free discharge through triangular notch
considering approach velocity.
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5. a)
A horizontal venturimeter with inlet diameter 20cm and throat
diameter 10cm is used to measure the flow of oil of specific graity
0.8. The discharge of oil through venturimeter is 60 lit/sec. Find the
reading of the oil – mercury differential manometer. Take Cd = 0.98.
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3. a)
b)
Describe stable and unstable equilibrium of submerged bodies. A 3+4
plate 0.05 mm distance from a fixed plate moves at 1.2 m/s and
requires a force of 2.2 N/m2 to maintain this speed. Find the viscosity
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of the fluid between the plates.
6. a)
b)
Find the expression for drag force on smooth sphere of diameter D,
moving with a uniform velocity v, in a fluid of density ρ and
dynamic viscosity μ.
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Derive impulse-momentum equation ∑Fx= ρQ(vm2)x- ρQ(vm1)x.
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7. Write short notes on any two:
a)
Boundary Layer Theorem
b)
Notches and weir
c)
Laminar and turbulent flow
2×5
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