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EC/DEC 2019/ECW422/401
UNIVERSITI TEKNOLOGI MARA
FINAL EXAMINATION
COURSE
:
FLUID MECHANICS/ELEMENTARY FLUID
MECHANICS
COURSE CODE
ECW422/401
EXAMINATION
DECEMBER 2019
TIME
3 HOURS
INSTRUCTIONS TO CANDIDATES
1.
This question paper consists of five (5) questions.
2.
Answer ALL questions in the Answer Booklet. Start each answer on a new page.
Do not bring any material into the examination room unless permission is given by the
invigilator.
Please check to make sure that this examination pack consists of:
i)
the Question Paper
ii)
an Answer Booklet - provided by the Faculty
Answer ALL questions in English.
DO NOT TURN THIS PAGE UNTIL YOU ARE TOLD TO DO SO
This examinationpaper consists of 9 printedpages
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EC/DEC 2019/ECW422/401
QUESTION 1
a) The force, P that is exerted on a spherical particle moving slowly through a liquid is given
by the equation below:
P = 3nnDV
where, u is the fluid viscosity [ML'2T], D is the particle diameter, and V is the particle
velocity. What is the dimensions of the constant, 3tt?
homogeneous. (C01-P01)(C2)
Determine if the equation is
(5 marks)
b) A liquid when poured into a graduated cylinder is found to weigh 6N occupying a volume
of 500 ml (millilitres). Determine its specific weight, density, and specific gravity.
(C01-P01)(C2)
(5 marks)
c) Water flows down an inclined fixed surface with the velocity profile shown in
Figure Q1 (c).Determine the magnitude and direction of the shearing stress on the fixed
surface for U = 3 ms"1 and h = 0.1 m. The dynamic viscosity for water, p. = 1.12 x IO3 ~
and the equation for velocity is given as ; (C01-P01)(C2)
" = 7y--y—
U
h
h2
Figure Q1 (c)
(5 marks)
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QUESTION 2
a) An inclined manometer is attached to a pipe A filled with water and pipe B which is full of
oil as shown in Figure Q2 (a). If the angle of inclination, 6 is 40° and the pressure different
between pipe A and pipe B is 10 kPa, determine the length, -e, given SG mercury = 13 6
and SG water = 1.0 (C01-P01)(C2)
10 cm
Water
7 cm
(5 marks)
b) In reference to Figure Q2 (a) determine the pressure in pipe A and pipe B, if the pressure
in pipe A is twice the pressure in pipe B and the length, { is maintained.(C01-P01)(C3)
(5 marks)
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EC/DEC 2019/ECW422/401
c) A 1.2 m tall concrete retaining wall is built as shown in Figure Q2 (c) with a gap of 0.4m
from the earth. During heavy rain, water fills the space between the wall and the earth to
a depth of 0.7m. Determine the force acting on the retaining wall and its point of location
(centre of pressure) if the wall is 3m wide (into the plane). (C02-P02)(C4)
A
1.2m
Earth
0.7 m
v
v
Figure Q2 (c)
(10 marks)
QUESTION 3
a) A 60 cm solid cube floats in water with a 15 cm thick oil layer on top as shown in
Figure Q3 (a). Determine the weight of the cube (C01-P01) (C2).
Oil (SG = 0.98)
Water
///////////////////
Figure Q3 (a)
(5 marks)
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EC/DEC 2019/ECW422/401
b) A rectangular floating pontoon bridge has depth of 7.6 m, width of 12 m and length of 10
m, and total weight of 140 kN as shown in Figure Q3 (b). (C02, P02)(C5)
i)
Determine the maximum load the pontoon bridge can sustain before it becomes totally
submerged.
ii) Check the stability of the pontoon bridge if a point load of 2800 kN is placed in the
middle of the top surface of the pontoon.
7.6 m
12m
Figure Q3 (b)
(10 marks)
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EC/DEC 2019/ECW422/401
QUESTION 4
a) Explain the principles of venturi meter for flow measurement. (C01-P01)(C2)
(5 marks)
b) A vertical venturi meter with a mercury manometer is used to measure flow rate of water
as shown in Figure Q4 (b). (C01-P01)(C4)
i)
Determine the theoretical volumetric flowrate of water through the venturi meter.
ii) If the discharge coefficient is 0.97, calculate the actual volumetric flow rate.
ho = 30 cm
h7 = 2 cm
hx = 14 cm
Dt = 12 cm
Figure Q4 (b)
(10 marks)
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EC/DEC 2019/ECW422/401
c) A 3.5m high large tank as shown in Figure Q4 (c) is initially filled with water to a depth of
3 m. The tank water surface is open to the atmosphere, and a sharp-edged 10 cm diameter
orifice at the bottom drains to the atmosphere through a horizontal 80m long pipe. The
total head loss of the system from point A to point B is 1.5 m. (C02-P02)(C3)
i)
Determine the velocity of flow at the exit point.
ii)
In order to drain the tank faster, a pump is installed near the tank exit. Determine the
pump head input necessary to establish an average water velocity of 6.5 ms"1 when
the tank is full.
3m
10 cm
80 m
B
Figure Q4 (c)
(10 marks)
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d) For the tank configuration shown in Figure Q4(d), determine the water depth, hA. If the
flow, Q is steady, and the water surface elevation of both tank A and B is unchanged.
Ignore all losses. (C02-P02)(C4)
Q
H
0.03 m diameter
hA
T
A
0.05 m diameter
hR = 2m
I
FB
Figure Q4 (d)
(10 marks)
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QUESTION 5
a) With the aid of a diagram, explain the kinematic of forces exerted by flowing fluids on a
horizontal pipe bend based on Newton's second law of motion. (C01-P01)(C2)
(5 marks)
b) A free jet of fluid strikes a wedge as shown in Figure Q5 (b) and is split into the two
streams at an angle of 30°. The horizontal and vertical components of force needed to
hold the wedge stationary are Fh and Fv respectively. Given the fluid is incompressible,
and the mass of water is negligible. Determine the force ratio Fh/Fv. (C02-P02)(C5)
v
Figure Q5(b)
(10 marks)
END OF QUESTION PAPER
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