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INTERNAL TEST1 KEY
ME2204 - FLUID MECHANICS AND MACHINERY
PART - A
1. Distinguish between ideal fluids and real fluids. (2)Real fluids:
1. It is compressible2. They are viscous in nature3. Shear stress always exists in such fluids.
Ideal fluids: Incompressible, no viscosity, Imaginary fluid.
2. What is specific gravity? (2)It is ratio of specific weight of fluid to specific weight of standard fluid. It can also
be defined as the ratio of mass density of fluid to mass density of standard fluid.Specific weight, S = density of liquid/density of standard liquid
3. Define compressibility and viscosity of a fluid. (2)Compressibility is defined as the ratio of the change in pressure to the rate of change in
pressure to the rate of change of volume due to the change in pressure
Bulk modulus , K = change in pressure/change in volume per unit volume
Viscosity is the property of a liquid which determines the amount of resistance to a
shearing stress. It can also be defined as the property of a fluid due to the movement of
one layer of fluid. The unit is N-S/M2
4. State Newtons law of viscosity. (2)According to Newtons law of viscosity, the shear force F acting between two
layers of fluid is proportional to the difference in their velocities due and area A of the
plate and inversely proportional to the distance between them.
5. Define capillarity. (2)Capillarity is a phenomenon of rise or fall of liquid surface relative to the
adjacent general level of liquid. This phenomenon is due to the combined effect ofcohesion and adhesion of liquid particles. The rise of liquid level is known as capillary
depression.
6. What is meant by continuum? (2)All substance is made up of molecules. Molecules inside the substance are in
constant motion and colloid with each other. In gases the molecules are not closely
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spaced. So, the study of of motion of individual molecule is described with help of
statistical methods. But in liquids, the molecules are closely spaced which create strong
intereste4d in the motion of individual molecules, but in the overall motion of the fluid.
And therefore, we consider the fluid as a continuous medium called continuum, i.e,
there is a continuous distribution of matter with no empty space.
7. State Bernoullis theorem as applicable to fluid flow. (2)Bernoullis equation states that as ideal incompressible fluid when the flow is
steady and continuous, the sum of pressure energy, kinetic energy and potential energy
is constant along the steam line
8. What are the assumptions made into derivation of the Bernoullis equation? (2)The liquid is ideal and incompressible
The flow is steady and continuousThe velocity is uniform over the cross section and is equal to mean velocity
The only forces acting on the fluids are the gravity force and the pressure force
All the frictional losses are negligible
9. Mention any three applications of Bernoullis equation. (2)Venturimeter
Orifice meter
Pitot meter
10.What do you understand by impulse momentum equation? (2)Impulse momentum equation states that the impulse of force acting on a fluid
mass in a short internal of time is equal to the change of momentum in the direction of
force.
PART B
11.(A) The space between two square flat parallel plates is filled with oil. Each side ofthe plate is 60cm. the thickness of the oil film is 12.5mm the upper plate, which moves
at 2.5 metre per sec requjires a force of 98.1 N to maintain the speed. Determine:
(i) The dynamic viscosity of the oil in poise, and(ii) The kinematic viscosity of the oil in stokes if the specific gravity of the oil is
0.95 [8]
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(B) Find the kinematic viscosity of an oil having density 981 kg/m3 . the shear stress at a point
in oil is 0.2452N/M2 and velocity gradient at that point is 0.2 per second. [8]
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12.(A) Define compressibility and bulk modulus. [4]
(B) Define vapor pressure [2]
(C) An oil of viscosity 5 poise is used for lubricating between a shaft and sleeve. The diameter
of the shaft is 0.5m and it rotates at 200 r.p.m. calculate the power lost in oil for a sleeve
length of 100mm. the thickness of oil film is 1.0mm. [6]
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D) Explain types of fluids. [4]
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13 (A) Derive continuity equation in three dimension. [10]
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(B) Derive Bernoullis equation from Eulers equation of motion. [6]
=
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14. (A) State the momentum equation. How will you apply momentum equation for
determining the force exerted by a flowing fluid on a pipe bend? [12]
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(B) Define Moment of Momentum equation. Where this equation is used? [4]
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15. (A) The water is flowing through a pipe having diameters 20 cm and 10 cm at sections 1
and 2 respectively. The rate of flow through pipe is 35 litres/sec. The section 1 is 6m above
the datum and section 2 is 4m above datum. If the pressure at section 1 is 39.24 N/cm2. Find
the intensity of pressure at section 2. [8]
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(B) A pipe of 300 mm diameter conveying 0.3 m3/s of water has a right angled bend in a
horizontal plane. Find the resultant force exerted on the bend if the pressure at inlet and
outlet of the bend are 24.525 N/cm2
and 23.544 N/cm2 [8]
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