Fluid Mechanics Part 3 Flashcards
Vena-contracta formed during flow of a liquid through an orificemeter has
minimum liquid cross-section.
more diameter compared to orifice diameter.
minimum velocity of fluid stream.
none of these.
minimum liquid cross-section.
As per Newton’s law of viscosity, the shear stress for a given rate of angular deformation of fluid is proportional to(where, u = fluid viscosity)
1/u
u
u2
1/u2
u
Horsepower increase of a centrifugal gas compressor without altering the volumetric flow rate will __________ the gas discharge pressure.
increase
decrease
not change
exponentially decrease
increase
In continuous fluidisation
solids are completely entrained.
the pressure drop is less than that for batch fluidisation.
there is no entrainment of solids.
velocity of the fluid is very small.
solids are completely entrained.
Glass pipes can be joined by
flanges
welding
soldering
bell and spigot joint
bell and spigot joint
If two capillary tubes of dia 0.5 mm and 1 mm are dipped in a pot containing mercury, then the rise of mercury is
same in both the tubes.
greater in 1 mm dia tube.
greater in 0.5 mm dia tube.
zero in both the tubes.
greater in 0.5 mm dia tube.
For laminar flow of a shear thinning liquid in a pipe, if the volumetric flow rate is doubled, the pressure gradient will increase by a factor of
2
<2
>2
44928
2
Weber number is the ratio of inertial force to __________ force.
surface tension
gravity
viscous
elastic
surface tension
ME Mach - inertial to Elastic
WS Weber - inertial to Surface tension
FG Froude - inertial to Gravitational
RV Reynold - inertial to Viscous
EP Euler - Pressure to inertial
The curve of metacentre for a floating body __________ the curve of buoyancy.
is always below
is the evolute of
intersects at right angle
is tangential to
is the evolute of
At what value of crank angle (roughly), no flow of water from or into the air vessel takes place in case of a double acting reciprocating pump ?
40 and 140
45 and 60
90 and 80
20 and 120
40 and 140
The range of a particular rotameter can be increased by
use of floats of different densities.
no means.
increasing the diameter of the float.
decreasing the diameter of the float.
use of floats of different densities.
Which of the following is dimensionless ?
Angular velocity
Fanning friction factor
Specific volume
None of these
Fanning friction factor
A liquid is pumped at the rate of 600 litres using 1000 rpm. If the rpm is changed to 1100, the liquid pumped is __________ litres.
600
660
1.1
60
660
A compressor that takes suction at a pressure below atmospheric and discharge against atmospheric pressure is called a __________ pump.
sump
volute
vacuum
submerged
vacuum
A bed of spherical particles (specific gravity 2.5) of uniform size 1500 um is 0.5 m in diameter and 0.5 m high. In packed bed state, the porosity may be taken as 0.4. Ergun’s equation for the above fluid-particle system (in SI units) is given below : delta- P/L = 375 x 10^3 VOM + 10.94 x 10^6 V^2OM (SI units) If water is to be used as the fluidising medium, in actual operation, the above bed has a height = 1 m. What is the porosity of the fluidised bed ?
0.2
0.5
0.7
0.8
0.7
Dimension of kinematic viscosity is
MLT^-1
L^2 . T^-1
L^2T
L^2 . T^-2
L^2 . T^-1
A streamline is a line in flow field,
that is traced by all the fluid particles passing through a given point.
along which a fluid particle travels.
such that at every point on it, the velocity is tangential to it.
none of these.
such that at every point on it, the velocity is tangential to it.
While starting an axial flow pump, its delivery valve should be kept
open
closed
either open or closed
none of these
closed
__________ forces do not act in case of fluid flow.
Elastic
Tensile
Vibratory
Centrifugal
Tensile
Non-colloidal solution is an example of the __________ fluid.
non-Newtonion
Newtonion
dilatent
pseudoplastic
Newtonion
Boundary layer separation is caused by the
reduction of pressure below vapour pressure.
reduction of pressure gradient to zero.
adverse pressure gradient.
reduction of boundary layer thickness to zero.
adverse pressure gradient.
Identification of pipelines carrying different liquids and gases is done by the __________ of the pipe.
diameter
colour
altitude
none of these
colour
Pick out the correct statement.
Human blood is a Newtonion fluid.
A Newtonion fluid obeys Newton’s law of cooling.
For a non-Newtonion fluid, a straight line passes through the origin in a plot between shear stress and shear gradient.
Thin lubricating oil is an example of a non-Newtonion fluid.
A Newtonion fluid obeys Newton’s law of cooling.
What is the unit of kinematic viscosity in SI unit ?
M^2/sec
N/m^2 . sec
Kg . sec/m
None of these
M^2/sec
Hydraulic __________ works on the principle of Pascal’s law of transmission of fluid pressure.
press
turbine
pump
coupling
press
A 2” gate valve fitted in a pipe is replaced by a similar globe valve. Pressure drop in gate valve was Δp. For the same discharge, the pressure drop across globe valve is
Δp
< Δp
> Δp
Δp²
> Δp
Remember: gate to globe > Δp
The contraction co-efficient for Borda’s mouthpiece (for frictionless fluid) is
0.1
0.5
0.94
1
0.5
Purpose of air lift pump is to
compress air.
lift compressed air.
lift water from a well by using compressed air.
lift air under negative pressure.
lift water from a well by using compressed air.
Pick out the correct statement pertaining to venturimeter.
A venturimeter with a fixed pressure drop discharges more, when the flow is vertically downward, than when the flow is vertically upward.
The co-efficient of contraction of a venturimeter is always unity.
For a fixed pressure drop, the discharge of a gas through a venturimeter is greater, when compressibility is taken into account, than when it is neglected.
none of these.
none of these.
For very low pressure and high discharge rate, the compressor used is a/an __________ compressor.
axial
reciprocating
rotary
none of these
rotary
Pumping of a corrosive liquid is generally preferred to be done by a __________ pump, as it can be made of a variety of materials including plastics.
piston
gear
positive displacement
sump
gear
What is the speed of sound (m/sec) in ordinary water ?
1500
330
1000
3000
1500
Two piping system are said to be equivalent, when the __________ are same.
fluid flow rate & friction loss
length & friction factor
diameter & friction factor
length & diameter
fluid flow rate & friction loss
Potential function is applicable only for __________ flow.
irrotational
turbulent
steady
none of these
irrotational
Which of the following exemplifies a three dimensional fluid flow ?
Fluid flow at the inlet to a nozzle
Fluid flow between parallel plates
Viscous fluid flow between converging plates
None of these
Fluid flow at the inlet to a nozzle
Volute of a centrifugal pump should be designed in a fashion, such that the
kinetic head gets converted into static head.
moving stream gradually reduces velocity.
mean velocity remains constant.
none of these.
kinetic head gets converted into static head.
The head loss due to sudden contraction is proportional to
velocity
velocity head
turbulence
none of these
velocity head
Cavitation occurs in a centrifugal pump when the suction pressure is
less than the vapour pressure of the liquid at that temperature.
greater than the vapour pressure of the liquid at that temperature.
equal to the vapour pressure.
equal to the developed head.
less than the vapour pressure of the liquid at that temperature.
An ideal plastic substance indicates no deformation, when stressed upto yield stress, but behaves like a Newtonion fluid beyond yield stress. Which of the following is an ideal plastic ?
Sewage sludge
Rubber latex
Blood
Sugar solution
Sewage sludge
The capacity of a centrifugal pump Can be increased by increasing the
impeller diameter or speed.
number of pumps and joining them in series,
number of pumps and joining them in parallel.
all of these
all of these
Which law is followed by the velocity distribution in the turbulent boundary layer?
Parabolic law
Linear law
Logarithmic law
None of these
Logarithmic law
The losses in open channel flow generally vary as the
inverse of the roughness.
first power of the roughness.
square of the velocity.
inverse square of hydraulic radius.
first power of the roughness.
Out of the following flow measuring devices, which one incurs the maximum installation cost as well as pressure loss ?
Flow nozzle
Venturimeter
Rotameter
Orificemeter
Venturimeter
For turbulent fluid flow in pipe, the expression for Prandtl one seventh power law is (where, r = pipe radius, x = distance).
V/Vmax = (x/r)^1/7
V/Vmax = (r/x)^1/7
V/Vmax = (x.r)^1/7
none of these
V/Vmax = (x/r)^1/7
Which of the following has the maximum compression ratio ?
Blower
Compressor
Vacuum pump
Fan
Vacuum pump
Scale up of agitator design requires
geometrical similarity only.
dynamic similarity only.
both geometrical and dynamic similarity.
all geometrical, dynamic and kinematic similarity.
all geometrical, dynamic and kinematic similarity.
The actual velocity at vena-contracta for flow through an orifice from a reservoir is given by
Cv . √2gH
Cc . √2gH
Cd . √2gH
Cv . Va
Cv . √2gH
The head loss in turbulent flow in pipe is proportional to (where, V = velocity of fluid through the pipe)
V²
1/V²
1/V
V
V²
Unsteady non-uniform flow is represented by flow through a/an
long pipe at constant rate.
long pipe at decreasing rate.
expanding tube at increasing rate.
expanding tube at constant rate.
expanding tube at increasing rate.
Remember: unsteady non-uniform expanding increasing
Prandtl number is a measure of the
heat conduction to viscosity of a fluid.
Cp/Cv of a fluid.
elastic force to pressure force in the fluid flow.
inertial force to elastic force in the fluid flow.
heat conduction to viscosity of a fluid.
A centrifugal pump has the following specifications: Power = 4 H.P.; Speed = 800 rpmHead = 8 metresFlow = 1000 litres/minutes.If its speed is halved, then the new head will be __________ metres.
2
4
8
5.5
2
In hindered settling, the particles are
placed farther from the wall.
not affected by other particles and the wall.
near each other,
none of these.
near each other,
A globe valve is the most suitable for applications, in which
fluid flow control is required.
fluid contains dispersed solid particles.
valve is required to be either fully open or fully closed.
one way flow is required.
fluid flow control is required.
__________ isused for measuring the static pressure exerted on the wall by a fluid flowing parallel to the wall in a pipeline.
Venturimeter
Pressure gauge
Pitot tube
Orificemeter
Pitot tube
One stoke (unit of kinematic viscosity) is equivalent to
1 cm^2/second
1 m^2/second
1 gm/cm. second
1 kg . m/second
1 cm^2/second
Air vessel of a reciprocating pump is initially filled with
atmospheric air
compressed air
water
none of these
compressed air
The ratio of inertial forces to gravity forces is called the __________ number.
Mach
Froude
Euler
Weber
Froude
ME Mach - inertial to Elastic
WS Weber - inertial to Surface tension
FG Froude - inertial to Gravitational
RV Reynold - inertial to Viscous
EP Euler - Pressure to inertial
Power required by a centrifugal pump is proportional to (where, D = diameter, N = r.p.m)
N^2D^3
ND^2
N^2D
N^3D^5
N^3D^5
Equivalent length of a pipe fitting is
dependent on Reynolds number.
independent of Reynolds number.
dependent on the length of the pipe.
none of these.
dependent on Reynolds number.
Buckingham-(pi) theorem states that in any physical problem including ‘n’ quantities having ‘m’ diamensions, the quantities can be arranged into __________ independent dimensionless parameters.
m
n
n-m
n/m
n-m
A fluid which has a linear relationship between the magnitude of applied shear-stress and the resulting rate of deformation is called a/an __________ fluid.
Newtonion
Non-Newtonion
ideal
incompressible
Newtonion
Existence of boundary layer in fluid flow is because of the
surface tension
fluid density
fluid viscosity
gravity forces
fluid viscosity
In case of laminar flow of fluid through a circular pipe, the
shear stress over the cross-section is proportional to the distance from the surface of the pipe.
surface of velocity distribution is a paraboloid of revolution, whose volume equals half the volume of circumscribing cylinder.
velocity profile varies hyperbolically and the shear stress remains constant over the cross-section.
average flow occurs at a radial distance of 0.5 r from the centre of the pipe (r = pipe radius).
surface of velocity distribution is a paraboloid of revolution, whose volume equals half the volume of circumscribing cylinder.
Which of the following facilitates close control of flow of fluids ?
Gate valve
Globe valve
Butterfly valve
Check valve
Globe valve
For an ideal fluid flow, Reynolds number is
2100
100
0
infinite
0
Stoke’s equation is valid in the Reynolds number range
0.01 to 0.1
0.1 to 2
2 to 10
10 to 100
0.01 to 0.1
When a fluid flows over a solid surface, the
velocity is uniform at any cross-section.
velocity gradient is zero at the solid surface.
resistance between the surface & the fluid is lesser as compared to that between the fluid layers themselves.
velocity is not zero at the solid surface.
velocity gradient is zero at the solid surface.
Pick out the wrong statement about cavitation.
Sudden reduction of pressure in a fluid flow system caused by flow separation, vortex formation or abrupt closing of valve leads to cavitation.
Cavitation may be caused due to boiling of liquid by decreasing the pressure resulting in formation & collapse of vapor cavities.
Cavitation begins at higher static pressure and lower velocity in larger diameter pipelines resulting in audible noise.
Large scale cavitation can not damage pipeline, restrict fluid flow and damage steam turbine blades.
Large scale cavitation can not damage pipeline, restrict fluid flow and damage steam turbine blades.
The maximum delivery pressure of a reciprocating compressor may be about __________ kg/cm².
1000
2000
3000
4000
4000
The velocity for subsonic flow in a pipeline
increases in the downstream direction.
is constant.
decreases in the downstream direction.
is independent of the area of flow.
increases in the downstream direction.
Permanent pressure loss in a well designed venturimeter is about __________ percent of the venturi differential.
1
10
30
50
10
The ratio of pressure forces to inertial forces is called the __________ number.
Froude
Euler
Reynold
Mach
Euler
ME Mach - inertial to Elastic
WS Weber - inertial to Surface tension
FG Froude - inertial to Gravitational
RV Reynold - inertial to Viscous
EP Euler - Pressure to inertial