CIVIL ENGINEERING
Paper: Fluid Mechanics & Hydrailics II
Semester IV
Note: Q1 is compulsory. Attempt any one question from each unit.
Q. 1
(a)
(b)
(c)
(d)
(e)
Q.2
(a)
(b)
Q.3
(a)
(b)
Q.4
(a)
(b)
Q.5
(a)
(b)
Paper Code: ETCE205
Marks: 75
What are factor that can change a laminar flow into a turbulent flow?
(5x5=25)
Differentiate between stream line body and bluff body?
What is the slip of a reciprocating pump? Why is it negative sometimes?
What are the important aspects of total energy line and hydraulic gradient line?
Define (i) unit speed (ii) Jet Ratio
(iii) manometric efficiency (iv) Hydraulic efficiency (v) NPSH
UNIT I
Prove that for a steady laminar flow between two fixed parallel plates, the velocity distribution
across a section is parabolic and that average velocity is 2/3rd of maximum velocity.
(6)
A pipe line 10 cm diameter carries glycerin of specific weight 1.3 and dynamic viscosity 7 poise. If
then maximum shear stress at the pipe wall is measured as 196.2 N/m2, calculate
(i)
Pressure gradient
(ii)
Discharge
(iii)
Reynolds Number
(iv) Velocity and shear stress at radius of 2.5 cm from pipe centre.
(6.5)
Distinguish between hydraulically smooth and rough pipes?
For turbulent flow in a pipe of 25 cm diameter, the centre line velocity is 2.25 m/s and the velocity
at a point 8 cm from the centre as measured by pitot tube is 1.95 m/s. find
(i) Friction velocity and wall shearing stress
(ii) average velocity and discharge through the pipe
(iii) friction factor
(iv) pipe roughness
(7.5)
Define physically and mathematically the concept of displacement, momentum and energy
thickness of boundary layer. Place them in order of their magnitudes.
(5)
UNIT II
Give reason for the following
(i)
telephone wires produce a humming noise in wind
(ii)
a spinning tennis ball curves in flight
(5)
(iii)
Terminal velocity of body is much higher in air as compared to that in water.
A television transmitting antenna is fixed on the top of a pipe, 30 meter high and 50 cm diameter,
which stands on a tall building. What will be the total drag of the pipe and the moment at its base
when it is exposed to a wind of inform velocity at 125 km/hr? How this moment will change if
diameter of pipe gradually changes from 50 cm at lease to 30 cm at the top? For turbulent flow,
average value of CD equal to 0.3, for air ρ = 1.2 kg/m3 and p = 1.8 X 10-5 Pas.
(7.5)
With the help of neat sketch, explain circulatory theory of lift and Magnus effect?
(4.5)
What is compound pipe? A piping system consists of these pipe arranged in stress
Pipe
Length
Diameter
AB
2000 m
40 cm
BC
1500 m
30 cm
CD
1000 m
20 cm
Q.6
Q.7
Transform it to an equivalent length of 30 cm diameter pipe.
(8)
UNIT III
Explain water hammer in pipes? Derive an expression for pressure rise due to rapid closure of value
in an elastic pipe?
(6.5)
(b)
Water from a main canal is siphoned to a branch canal over an embankment by means of wrought
iron pipes of 9 cm diameter. The length of pipe up to summit is 25m and the total length is 65m,
water surface elevation in the branch canal is 10 m below main canal. What is maximum permissible
height of summit above the water level in the main canal so that water pressure in summit may not
fall below 0.2 bar absolute, Barometer reading being 10m of water? Take friction factor f= 0.0075 (6)
(a)
(i)
(ii)
(iii)
(b)
(i)
(ii)
Q. 8(a)
Q.9
(b)
(a)
(b)
Explain briefly how hydraulic reaction turbines differ from impulse turbines
State the purpose of draft tube in reaction water turbine.
Why does cavitations occur and how it can be checked in fluid mechanics
(2)
(2)
(2.5)
Derive an expression for specific speed of a hydrodynamic machine and discuss how the
classification of runners is based on specific speed.
(4)
Explain the factor which decided the choice for particular turbine for hydro power project? (2)
UNIT IV
A pelton wheel of 1.2 m mean bucket diameter works under a head of 650 m. the jet deflection 165 0
and its relative velocity is reduced over the buckets by 15% due to friction. If the water is to leave
bucket without any whirl. Determine
(a)
Rotational speed of the wheel
(b)
Ratio of bucket speed to get velocity
(c)
Impulsive force and power developed by wheel
(d)
Available power and power input to buckets
(e)
η of wheel. Take Kv = 0.97
(6.5)
Derive an expression for head developed by impeller of rotodynamic pump.
(6)
A single acting reciprocating pump has a stroke length of 15 pipe is 7 cm, the suction m long and the
ratio of suction pipe diameter to plunger diameter is 3/4. The water level in the sump is 2.5 m below
the axis of the pump cylinder and pipe connecting the sump and pump cylinder is 7.5 cm diameter.
If the crank is running at 75 rpm, determine the pressure head on the piston at the beginning, mid
and the end of the suction stroke. Take f= 0.1.
(7.5)
Give reason for utility of providing air vessels on the suction and delivery sides of reciprocating
pump?
(5)
(b)
What is priming. Explain clearly why priming is essential before starting a centrifugal pump?