Explore topic-wise MCQs in Fluid Mechanics and Hydraulic Machinery.

This section includes 176 Mcqs, each offering curated multiple-choice questions to sharpen your Fluid Mechanics and Hydraulic Machinery knowledge and support exam preparation. Choose a topic below to get started.

51.

The stream function in a two dimensional flow field is given by = x y The magnitude of the velocity at point (1, 1) is

A. 2
B. 2
C.
D. 4
E. 8
Answer» C.
Discussion
52.

The velocity components in the x and y directions are given by u = xy3 x2y, v = xy2 ( 3 / 4 )y4. The value of for a possible flow field involving an incompressible fluid is

A. 3
Answer» E.
Discussion
53.

Bodies in flotation to be in stable equilibrium the necessary and sufficient condition is that the centre of gravity is located below the ____.

A. Located between the metacentre.
B. Located under the metacentre.
C. Located below the metacentre.
D. metacentre.
Answer» D. metacentre.
Discussion
54.

A two-dimensional flow field has velocities along the x and y directions given by u = x t and v = 2xyt respectively, where t is time. The equation of streamline is

A. x y = constant
B. xy = constant
C. xy = constant
D. not possible to determine
Answer» B. xy = constant
Discussion
55.

A fluid flow is represented by the velocity field

A. x 2y = 0
B. 2x + y = 0
C. 2x y = 0
D. x + 2y = 0
Answer» D. x + 2y = 0
Discussion
56.

In a flow field the stream lines and equipotential lines

A. are parallel
B. Cut at any angle
C. Are orthogonal every where in the field
D. Cut orthogonal except at the stagnation points
Answer» E.
Discussion
57.

A streamlined body is defined as a body about which

A. The flow is laminar
B. The flow is along the streamlines
C. The flow separation is suppressed
D. The drag is zero
Answer» D. The drag is zero
Discussion
58.

For the stability of a floating body, under the influence of gravity alone, which of the following is TRUE?

A. Metacenter should be below centre of gravity.
B. Metacenter should be above centre of gravity.
C. Metacenter and centre of gravity must lie on the same horizontal line.
D. Metacenter and centre of gravity must lie on the same vertical line.
Answer» C. Metacenter and centre of gravity must lie on the same horizontal line.
Discussion
59.

For the laminar flow of water oyer a sphere, the drag coefficient C

A. 100N
B. 18N
C. 20N
D. 40N
Answer» D. 40N
Discussion
60.

Water ( = 1000 kg/m ) flows through a venturimeter with inlet diameter 80 mm and throat diameter 40 mm. The inlet and throat gauge pressures are measured to be 400 kPa and 130 kPa respectively. Assuming the venturimeter to be horizontal and neglecting friction, the inlet velocity (in m/s) is ________.

A. 2m/s
B. 8m/s
C. 9m/s
D. 6m/s
Answer» E.
Discussion
61.

In the case of turbulent flow of a fluid though a circular tube (as compared to the case of laminar flow at the same flow rate) the maximum velocity is _________shear stress at the wall is _______, and the pressure drop across a given length is __________ The correct words for the blanks are, respectively

A. higher, higher, higher
B. higher, lower, lower
C. lower, higher, higher
D. lower, higher, lower
Answer» D. lower, higher, lower
Discussion
62.

For a fluid flow through a divergent pipe of length L having inlet and outlet radii of R

A. <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>2Q(R<sub>1</sub> - R<sub>2</sub>)</center></td></tr><tr><td style="text-align: center;"> LR <sub>2</sub></td></tr></table>
B. <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>2Q (R<sub>1</sub> - R<sub>2</sub>)</center></td></tr><tr><td style="text-align: center;"> LR <sub>2</sub></td></tr></table>
C. <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>2Q (R<sub>1</sub> - R<sub>2</sub>)</center></td></tr><tr><td style="text-align: center;"> LR<sub>5</sub><sub>2</sub></td></tr></table>
D. <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>2Q (R<sub>2</sub> - R<sub>1</sub>)</center></td></tr><tr><td style="text-align: center;"> LR<sub>5</sub><sub>2</sub></td></tr></table>
Answer» D. <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>2Q (R<sub>2</sub> - R<sub>1</sub>)</center></td></tr><tr><td style="text-align: center;"> LR<sub>5</sub><sub>2</sub></td></tr></table>
Discussion
63.

Prandtl's mixing length in turbulent flow signifies

A. the average distance perpendicular to the mean flow covered by the mixing particles
B. the ratio of mean free path to characteristic length of the flow field
C. the wavelength corresponding to the lowest frequency present in the flow field
D. the magnitude of turbulent kinetic energy
Answer» B. the ratio of mean free path to characteristic length of the flow field
Discussion
64.

Consider the turbulent flow of a fluid through a circular pipe of diameter D.Identify the correct pair of statements. I. The fluid is well-mixed

A. I and III
B. II and IV
C. II and III
D. I and IV
Answer» E.
Discussion
65.

A centrifugal pump is required to pump water to an open water tank situated 4 km away from the location of the pump through a pipe of diameter 0.2 m having Darcy's friction factor of 0.01. The average speed of water in the pipe is 2 m/s. If it is to maintain a constant head of 5 m in the tank, neglecting other minor losses, the absolute discharge pressure at the pump exit is

A. 0.449 bar
B. 5.503 bar
C. 44.911 bar
D. 55.203 bar
Answer» C. 44.911 bar
Discussion
66.

Water enters a circular pipe of length L = 5.0 m and diameter D = 0.20 m with Reynolds number Re

A. 577
B. 500
C. 520
D. 5.00
Answer» C. 520
Discussion
67.

A centrifugal pump running at 500 rpm and at its maximum efficiency is delivering a head of 30 m at a flow rate of 60 liters per minute. If the rpm is changed to 1000, then the head H in meters and flow rate Q in liters per minute at maximum efficiency are estimated to be

A. H = 60, Q = 120
B. H = 120, Q= 120
C. H = 60, Q = 480
D. H = 120, Q = 30
Answer» C. H = 60, Q = 480
Discussion
68.

Water at 25 C is flowing throug a 1.0 km long G.I. pipe of 200 mm diameter at the rate of 0.07 m /s. If value of Darcy friction factor for this pipe is 0.02 and density of water is 1000 kg/m , the pumping power (in kW) required to maintain the flow is

A. 1.8
B. 17.4
C. 20.5
D. 41.0
Answer» C. 20.5
Discussion
69.

In terms of speed of rotation of the impeller N, discharge Q and change in total head H, through the machine, the specific speed for pump is ____

A. <table><tr><td rowspan="2">N<sub>s</sub> = </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>H<sup>4/3</sup></center></td><td rowspan="2"></td></tr><tr><td style="text-align: center;">N <span style=" text-decoration: overline;">Q</span></td></tr></table>
B. <table><tr><td rowspan="2">N<sub>s</sub> = </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>NQ</center></td><td rowspan="2"></td></tr><tr><td style="text-align: center;">H<sup>4/3</sup></td></tr></table>
C. <table><tr><td rowspan="2">N<sub>s</sub> = </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>N <span style=" text-decoration: overline;">Q</span></center></td><td rowspan="2"></td></tr><tr><td style="text-align: center;">H<sup>4/3</sup></td></tr></table>
D. <table><tr><td rowspan="2">N<sub>s</sub> = </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>N <span style=" text-decoration: overline;">Q</span></center></td><td rowspan="2"></td></tr><tr><td style="text-align: center;">H</td></tr></table>
Answer» D. <table><tr><td rowspan="2">N<sub>s</sub> = </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>N <span style=" text-decoration: overline;">Q</span></center></td><td rowspan="2"></td></tr><tr><td style="text-align: center;">H</td></tr></table>
Discussion
70.

The Newtonian fluid has the following velocity field:

A. 6
B. 2
C. 12
D. 4
Answer» B. 2
Discussion
71.

The velocity potential function for a source varies with the distance r as

A. 1/r
B. 1/r
C. er
D. In r
Answer» E.
Discussion
72.

A Prandtl tube (Pitot-static tube with C = 1) is used to measure the velocity of water. The differential manometer reading is 10 mm of liquid coiumn with a relative density of 10. Assuming g = 9.8 m/s , the velocity of water (in m/s) is _____ .

A. 8 m/ s
B. 2 m/ s
C. 1.328 m/ s
D. 1.25m/ s
Answer» D. 1.25m/ s
Discussion
73.

Velocity vector of a flow field is given as

A. 4 - &jcirc;
B. 4 - k
C. - 4&jcirc;
D. - 4k
Answer» E.
Discussion
74.

The viscous laminar flow of air over a flat plate results in the formation of a boundary layer. The boundary layer thickness at the end of the plate of length L is

A. 44.42%
B. 41.42%
C. 43.42%
D. 40.42%
Answer» C. 43.42%
Discussion
75.

The mass flow rate (in kg/s) across the section q r is

A. zero
B. 0.05
C. 0.10
D. 0.15
Answer» C. 0.10
Discussion
76.

The integrated drag force (in N) on the plate, between p s, is

A. 0.67
B. 0.33
C. 0.17
D. zero
Answer» D. zero
Discussion
77.

An idealized centrifugal pump (blade outer radius of 50 mm) consumes 2 kW power while running at 3000 rpm. The entry of the liquid into the pump is axial and exit from the pump is radial with respect to impeller. If the losses are neglected, then the mass flow rate of the liquid through the pump is ____ kg/s (round off to two decimal places).

A. 8.11 kg/s
B. 9.11 kg/s
C. 7.11 kg/s
D. 5.11 kg/s
Answer» B. 9.11 kg/s
Discussion
78.

An ideal water jet with volume flow rate of 0.05 m

A. 56.41 mm
B. 55.41 mm
C. 66.41 mm
D. 76.41 mm
Answer» B. 55.41 mm
Discussion
79.

A pump handling a liquid raises its pressure from 1 bar to 30 bar. Take the density of the liquid as 990 kg/m

A. 0.10
B. 0.30
C. 2.50
D. 2.93
Answer» E.
Discussion
80.

Shown below are three cylindrical gates which restrain water in a 2 D Channel. Which gate experiences the maximum vertical component, the minimum vertical component and the maximum horizontal component of the hydro static force?

A.
B. <img src="http://images.interviewmania.com/wp-content/uploads/2019/10/72.png">
C. <img src="http://images.interviewmania.com/wp-content/uploads/2019/10/73.png">
D. <img src="http://images.interviewmania.com/wp-content/uploads/2019/10/74.png">
E. None of these
Answer» E. None of these
Discussion
81.

Water flows through two different pipes A and B of the same circular cross-section but at different flow rates. The length of pipe A is 1.0 m and that of pipe B is 2.0 m. The flow in both the pipes is laminar and fully developed. If the frictional head loss across the length of the pipes is same, the ratio of volume flow rates Q

A. 0.5
B. 0.4
C. 0.6
D. 0.3
Answer» B. 0.4
Discussion
82.

Existence of velocity potential implies that

A. Fluid is in continuum
B. Fluid is irrotational
C. Fluid is ideal
D. Fluid is compressible
Answer» C. Fluid is ideal
Discussion
83.

For a two-dimensional in compressible flow field given by u = A(x i yj ), where A > 0, which one of the following statements is FALSE?

A. A
B. B
C. C
D. D
Answer» D. D
Discussion
84.

Consider laminar flow of water over a flat plate of length 1 m. If the boundary layer thickness at a distance of 0.25 m from the leading edge of the plate is 8 mm, the boundary layer thickness (in mm), at a distance of 0.75 m, is ______

A. 13
B. 13.86
C. 14.82
D. 13.98
Answer» C. 14.82
Discussion
85.

For a fully developed flow of water in a pipe having diameter 10 cm, velocity 0.1 m/s and kinematic viscosity 10 5 m

A. 0.364
B. 0.264
C. 0.064
D. 0.164
Answer» D. 0.164
Discussion
86.

Oil (kinematic viscosity,

A. 21.24
B. 23.25
C. 22.25
D. 22
Answer» D. 22
Discussion
87.

In a simple concentric shaft-bearing arrangement, the lubricant flows in the 2 mm gap between the shaft and the bearing. The flow may be assumed to be a plane Couette flow with zero pressure gradient. The diameter of the shaft is 100 mm and its tangential speed is 10 m/s. The dynamic viscosity of the lubricant is 0.1 kg/ms. The frictional resisting force (in Newton) per 100 mm length of the bearing is

A. 15.707
B. 15.706
C. 15.708
D. 15.709
Answer» B. 15.706
Discussion
88.

Water flows through a pipe having an inner radius of 10 mm at the rate of 36 kg/hr at 25 C. The viscosity of water at 25 C is 0.001 kg/ms. The Reynolds number of the flow is ______.

A. 0.1
B. 0.2
C. 0.3
D. 0.4
Answer» B. 0.2
Discussion
89.

Consider a fully developed steady laminar flow of an in compressible fluid with viscosity . through a circular pipe of radius R, Given that the velocity at a radial location of R/2 from the centerline of the pipe is U

A. 3.21
B. 5.24
C. 6.24
D. None of these
Answer» E.
Discussion
90.

Consider fluid flow between two infinite horizontal plates when are parallel (the gap between them being 50 mm), The top plate is sliding parallel to the stationary bottom plate at a speed of 3 m/s.

A. 26.4
B. 26.9
C. 26.7
D. 26.8
Answer» B. 26.9
Discussion
91.

For a fully developed laminar flow of water (dynamic viscosity 0.001 Pa-s) through a pipe radius 5 cm, the axial pressure gradient is 10 Pa/m. The magnitude of axial velocity (in m/s) at a radial location of 0.2 cm is ________.

A. 6.24
B. 6.29
C. 6.26
D. 6.34
Answer» B. 6.29
Discussion
92.

Air ( = 1.2 kg/m

A. 0.1159
B. 0.0259
C. 0.0157
D. 0.0159
Answer» E.
Discussion
93.

For a steady flow, the velocity field is V = ( x + 3y) i + (2xy)j. The magnitude of the acceleration of a particle at (1, - 1) is

A. 2
B. 1
C. 2
D. <span style=" text-decoration: overline;">5</span>
E. 0
Answer» D. <span style=" text-decoration: overline;">5</span>
Discussion
94.

For a two-dimensional flow, the velocity field is

A. 2 and 3
B. 1 and 3
C. 1 and 2
D. 3 and 4
Answer» C. 1 and 2
Discussion
95.

For a Pelton wheel with a given water jet velocity, the maximum output power from the Pelton wheel is obtained when the ratio of the bucket speed to the water jet speed is ______ (correct to two decimal places).

A. <table><tr><td rowspan="2">u =</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>v</center></td><td rowspan="2"></td></tr><td align="center">2</td></table>
B. <table><tr><td rowspan="2">u =</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>2</center></td><td rowspan="2"></td></tr><td align="center">v</td></table>
C. <table><tr><td rowspan="2">v =</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>u</center></td><td rowspan="2"></td></tr><td align="center">2</td></table>
D. None of these
Answer» B. <table><tr><td rowspan="2">u =</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>2</center></td><td rowspan="2"></td></tr><td align="center">v</td></table>
Discussion
96.

Consider two hydraulic turbines having identical specific speed and effective head at the inlet. If the speed ratio (N

A. 0.26
B. 0.24
C. 0.25
D. 0.35
Answer» D. 0.35
Discussion
97.

Which of the following statements are TRUE, when the cavitation parameter = 0?

A. i, ii and iv
B. only ii and iii
C. only i and iii
D. i, ii and iii
Answer» E.
Discussion
98.

A phenomenon is modeled using-n dimensional variables with k primary dimensions. The number of non-dimensional variables is

A. k
B. n
C. n - k
D. n + k
Answer» D. n + k
Discussion
99.

For steady, fully developed flow Inside straight pipe of diameter D, neglecting gravity effects, the pressure drop p over a length L and the wall shear stress W are related by

A. <table><tr><td rowspan="2"> W =</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center> pD</center></td><td rowspan="2"></td></tr><td align="center">4L</td></table>
B. <table><tr><td rowspan="2"> W =</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center> pD </center></td><td rowspan="2"></td></tr><td align="center">4L </td></table>
C.
D. <table><tr><td rowspan="2"> W =</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center> pD</center></td><td rowspan="2"></td></tr><td align="center">2L</td></table>
E. <table><tr><td rowspan="2"> W =</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>4 pD</center></td><td rowspan="2"></td></tr><td align="center">D</td></table>
Answer» B. <table><tr><td rowspan="2"> W =</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center> pD </center></td><td rowspan="2"></td></tr><td align="center">4L </td></table>
Discussion
100.

The aerodynamic drag on a sports car depends on its shape. The car has a drag coefficient of 0.1 with the windows and the roof closed. With t he windows and t he r oof open, t he dr ag coefficient becomes 0.8. The car travels at 44 km/h with the windows and roof closed. For the same amount of power needed to overcome the aerodynamic drag, the speed of the car with the windows and roof open (round off to two decimal places), is ____ km/h. (The density of air and the frontal area may be assumed to be constant.

A. 22km/h
B. 21km/h
C. 23km/h
D. 24km/h
Answer» B. 21km/h
Discussion