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180+ more mcqs Solved MCQs

in Fluid Mechanics (FM)

These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Civil Engineering .

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151.	If a sphere of diameter 1 cm falls in castor oil of kinematic viscosity 10 stokes, with a terminal velocity of 1.5 cm/sec, the coefficient of drag on the sphere is
A.	less than 1
B.	between 1 and 100
C.	160
D.	200
Answer» C. 160

discuss

152.	In case of an airfoil, the separation of flow occurs
A.	at the extreme rear of body
B.	at the extreme front of body
C.	midway between rear and front of body
D.	any where between rear and front of body depending upon Reynolds number
Answer» A. at the extreme rear of body

discuss

153.	When an ideal fluid flows past a sphere,
A.	highest intensity of pressure occurs around the circumference at right angles to flow
B.	lowest pressure intensity occurs at front stagnation point
C.	lowest pressure intensity occurs at rear stagnation point
D.	total drag is zero
Answer» D. total drag is zero

discuss

154.	With the same cross-sectional area and immersed in same turbulent flow, the largest total drag will be on
A.	a circular disc of plate held normal to flow
B.	a sphere
C.	a cylinder
D.	a streamlined body
Answer» A. a circular disc of plate held normal to flow

discuss

155.	In which of the following the friction drag is generally larger than pressure drag?
A.	a circular disc or plate held normal to flow
B.	a sphere
C.	a cylinder
D.	an airfoil
Answer» D. an airfoil

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156.	For hydro-dynamically smooth boundary, the friction coefficient for turbulent flow is
A.	constant
B.	dependent only on Reynolds number
C.	a function of Reynolds number and relative roughness
D.	dependent on relative roughness only
Answer» B. dependent only on Reynolds number

discuss

157.	The value of friction factor ‘f’ for smooth pipes for Reynolds number 106 is approximately equal to
A.	0.1
B.	0.01
C.	0.001
D.	0.0001
Answer» B. 0.01

discuss

158.	For laminar flow in a pipe of circular cross-section, the Darcy’s friction factor f is
A.	directly proportional to Reynolds number and independent of pipe wall roughness
B.	directly proportional to pipe wall roughness and independent of Reynolds number
C.	inversely proportional to Reynolds number and indpendent of pipe wall roughness
D.	inversely proportional to Reynolds number and directly proportional to pipe wall roughness
Answer» C. inversely proportional to Reynolds number and indpendent of pipe wall roughness

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159.	Separation of flow occurs when
A.	the pressure intensity reaches a minimum
B.	the cross-section of a channel is reduced
C.	the boundary layer comes to rest
D.	all of the above
Answer» C. the boundary layer comes to rest

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160.	The ratio of average velocity to maximum velocity for steady laminar flow in circular pipes is
A.	1/2
B.	2/3
C.	3/2
D.	2
Answer» A. 1/2

discuss

161.	The distance from pipe boundary, at which the turbulent shear stress is one-third die wall shear stress, is (where R is the radius of pipe.)
A.	1/3 R
B.	1/2 R
C.	2/3 R
D.	3/4R
Answer» A. 1/3 R

discuss

162.	The discharge of a liquid of kinematic viscosity 4 cm2/sec through a 8 cm dia-meter pipe is 3200n cm7sec. The type of flow expected is
A.	laminar flow
B.	transition flow
C.	turbulent flow
D.	not predictable from the given data
Answer» A. laminar flow

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163.	The Prartdtl mixing length is
A.	zero at the pipe wall
B.	maximum at the pipe wall
C.	independent of shear stress
D.	none of the above
Answer» A. zero at the pipe wall

discuss

164.	The velocity distribution for laminar flow through a circular tube
A.	is constant over the cross-section
B.	varies linearly from zero at walls to maximum at centre
C.	varies parabolically with maximum at the centre
D.	none of the above
Answer» C. varies parabolically with maximum at the centre

discuss

165.	A fluid of kinematic viscosity 0.4 cm2/sec flows through a 8 cm diameter pipe. The maximum velocity for laminar flow will be
A.	less than 1 m/sec
B.	1 m/sec
C.	1.5 m/sec
D.	2 m/sec
Answer» B. 1 m/sec

discuss

166.	The losses are more in
A.	laminar flow
B.	transition flow
C.	turbulent flow
D.	critical flow
Answer» C. turbulent flow

discuss

167.	The wake
A.	always occurs before a separation point
B.	always occurs after a separation point
C.	is a region of high pressure intensity
D.	none of the above
Answer» B. always occurs after a separation point

discuss

168.	The maximum thickness of boundary layer in a pipe of radius r is
A.	0
B.	r/2
C.	r
D.	2r
Answer» C. r

discuss

169.	The hydraulic grade line is
A.	always above the centre line of pipe
B.	never above the energy grade line
C.	always sloping downward in the direction of flow
D.	all of the above
Answer» B. never above the energy grade line

discuss

170.	Two pipe systems are said to be equivalent when
A.	head loss and discharge are same in two systems
B.	length of pipe and discharge are same in two systems
C.	friction factor and length are same in two systems
D.	length and diameter are same in two systems
Answer» A. head loss and discharge are same in two systems

discuss

171.	In series-pipe problems
A.	the head loss is same through each pipe
B.	the discharge is same through each pipe
C.	a trial solution is not necessary
D.	the discharge through each pipe is added to obtain total discharge
Answer» B. the discharge is same through each pipe

discuss

172.	Select the correct statement.
A.	The absolute roughness of a pipe de-creases with time.
B.	A pipe becomes smooth after using for long time.
C.	The friction factor decreases with time.
D.	The absolute roughness increases with time.
Answer» D. The absolute roughness increases with time.

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173.	A valve is suddenly closed in a water main in wl.ich the velocity is 1 m/sec and velocity of pressure wave is 981 m/ sec. The inertia head at the valve will be
A.	1 m
B.	10m
C.	100m
D.	none of the above
Answer» C. 100m

discuss

174.	The speed of a pressure wave through a pipe depends upon
A.	the length of pipe
B.	the viscosity of fluid
C.	the bulk modulus for the fluid
D.	the original head
Answer» C. the bulk modulus for the fluid

discuss

175.	When time of closure tc = L/v0 (where L is length of pipe and v0 is speed of pressure wave), the portion of pipe length subjected to maximum head is
A.	L/4
B.	L/3
C.	L/2
D.	L
Answer» A. L/4

discuss

176.	If the elevation of hydraulic grade line at the junction of three pipes is above the elevation of reservoirs B and C and below reservoir A, then the direction of flow will be
A.	from reservoir A to reservoirs B and C
B.	from reservoir B to reservoirs C and A
C.	from reservoir C to reservoirs A and B
D.	unpredictable
Answer» C. from reservoir C to reservoirs A and B

discuss

177.	The length of a pipe is 1 km and its diameter is 20 cm. If the diameter of an equivalent pipe is 40 cm, then its length is
A.	32 km
B.	20 km
C.	8 km
D.	4 km
Answer» A. 32 km

discuss

178.	Two pipes of same length and diameters d and 2d respectively are connected in series. The diameter of an equivalent pipe of same length is
A.	less than d
B.	between d and 1.5 d
C.	between 1.5 d and 2d
D.	greater than 2d
Answer» A. less than d

discuss ⁽¹⁾

179.	The horse power transmitted through a pipe is maximum when the ratio of loss of head due to friction and total head supplied is
A.	1/3
B.	1/4
C.	1/2
D.	2/3
Answer» A. 1/3

discuss

180.	The boundary layer thickness at a distance of l m from the leading edge of a flat plate, kept at zero angle of incidence to the flow direction, is O.l cm. The velocity outside the boundary layer is 25 ml sec. The boundary layer thickness at a distance of 4 m is (Assume that boundary layer is entirely laminar.)
A.	0.40 cm
B.	0.20 cm
C.	0.10 cm
D.	0.05 cm
Answer» B. 0.20 cm

discuss

181.	Drag force is a function of i) projected area of the body ii) mass density of the fluid iii) velocity of the body The correct answer is
A.	(i) and (ii)
B.	(i) and (iii)
C.	(ii) and (iii)
D.	(i), (ii) and (iii)
Answer» D. (i), (ii) and (iii)

discuss

182.	The correct relationship among displacement thickness d, momentum thickness m and energy thickness e is
A.	d > m > e
B.	d > e > m
C.	e > m > d
D.	e > d > m
Answer» D. e > d > m

discuss

183.	For laminar flow in circular pipes, the Darcy’s friction factor f is equal to
A.	16/Re
B.	32/ Re
C.	64/ Re
D.	none of the above where R,, is Reynolds number.
Answer» C. 64/ Re

discuss

184.	Surge wave in a rectangular channel is an example of i) steady flow ii) unsteady flow iii) uniform flow iv) non-uniform flow The correct answer is
A.	(i) and (iii)
B.	(ii) and (iii)
C.	(i) and (:v)
D.	(ii) and (iv)
Answer» D. (ii) and (iv)

discuss

180+ more mcqs Solved MCQs

If a sphere of diameter 1 cm falls in castor oil of kinematic viscosity 10 stokes, with a terminal velocity of 1.5 cm/sec, the coefficient of drag on the sphere is

In case of an airfoil, the separation of flow occurs

When an ideal fluid flows past a sphere,

With the same cross-sectional area and immersed in same turbulent flow, the largest total drag will be on

In which of the following the friction drag is generally larger than pressure drag?

For hydro-dynamically smooth boundary, the friction coefficient for turbulent flow is

The value of friction factor ‘f’ for smooth pipes for Reynolds number 106 is approximately equal to

For laminar flow in a pipe of circular cross-section, the Darcy’s friction factor f is

Separation of flow occurs when

The ratio of average velocity to maximum velocity for steady laminar flow in circular pipes is

The distance from pipe boundary, at which the turbulent shear stress is one-third die wall shear stress, is (where R is the radius of pipe.)

The discharge of a liquid of kinematic viscosity 4 cm2/sec through a 8 cm dia-meter pipe is 3200n cm7sec. The type of flow expected is

The Prartdtl mixing length is

The velocity distribution for laminar flow through a circular tube

A fluid of kinematic viscosity 0.4 cm2/sec flows through a 8 cm diameter pipe. The maximum velocity for laminar flow will be

The losses are more in

The wake

The maximum thickness of boundary layer in a pipe of radius r is

The hydraulic grade line is

Two pipe systems are said to be equivalent when

In series-pipe problems

Select the correct statement.

A valve is suddenly closed in a water main in wl.ich the velocity is 1 m/sec and velocity of pressure wave is 981 m/ sec. The inertia head at the valve will be

The speed of a pressure wave through a pipe depends upon

When time of closure tc = L/v0 (where L is length of pipe and v0 is speed of pressure wave), the portion of pipe length subjected to maximum head is

If the elevation of hydraulic grade line at the junction of three pipes is above the elevation of reservoirs B and C and below reservoir A, then the direction of flow will be

The length of a pipe is 1 km and its diameter is 20 cm. If the diameter of an equivalent pipe is 40 cm, then its length is

Two pipes of same length and diameters d and 2d respectively are connected in series. The diameter of an equivalent pipe of same length is

The horse power transmitted through a pipe is maximum when the ratio of loss of head due to friction and total head supplied is

Drag force is a function of i) projected area of the body ii) mass density of the fluid iii) velocity of the body The correct answer is

The correct relationship among displacement thickness d, momentum thickness m and energy thickness e is

For laminar flow in circular pipes, the Darcy’s friction factor f is equal to

Surge wave in a rectangular channel is an example of i) steady flow ii) unsteady flow iii) uniform flow iv) non-uniform flow The correct answer is

Drag force is a function of
i) projected area of the body
ii) mass density of the fluid
iii) velocity of the body
The correct answer is

Surge wave in a rectangular channel is an example of
i) steady flow ii) unsteady flow iii) uniform flow iv) non-uniform flow
The correct answer is