Fluid Mechanics Flashcards
The fluid property, due to which, mercury does not wet the glass is
surface tension
Laminar flow of a Newtonion fluid ceases to exist, when the Reynolds number exceeds
2100
When the momentum of one fluid is used for moving another fluid, such a device is called a/an
jet pump
The head loss in turbulent flow in a pipe varies
as (velocity)^2
Most commonly used joint in the underground pipe lines is the
sleevejoint
Schedule number of a pipe, which is a measure of its wall thickness, is given by
1000 P’/S
The net positive suction head (NPSH) of a centrifugal pump is defined as the sum of the velocity head and the pressure head at the
suction minus vapor pressure of the liquid at suction temperature.
With increasing flow rate, the hydraulic efficiency of a centrifugal pump
monotonically decreases.
The velocity profile for turbulent flow through a closed conduit is
logarithmic
In case of hydraulically smooth pipe, the resistance to flow depends only on the Reynolds number, whereas for a hydraulically rough pipe, the resistance to flow is governed by the relative roughness. Two pipes are said to have the same hydraulic roughness, when they have equal values of
friction co-efficient for flows at equal Reynold number.
Water hammer in a pipeline results from the
rapid pressure change due to a rapid change in the rate of flow.
Molten soap mass is transported by a __________ pump.
centrifugal
Which of the following denotes the effect of compressibility in fluid flow ?
Mach number
Nominal size of the discharge pipe of a pump is usually __________ the nominal size of the inlet pipe.
smaller than
The terminal velocity of a small sphere settling in a viscous fluid varies as the
inverse of the fluid viscosity.
If the discharge of a centrifugal pump is throttled, then its suction lift
increases
Foot valves provided in pumps are __________ valves.
directional control
At high Reynolds number
inertial forces control and viscous forces are unimportant.
Power loss in an orificemeter is __________ that in a venturimeter.
more than
The terminal velocity of a particle moving through a fluid varies as dpn. What is the value of n’ for Newton’s law regime ?
0.5
What is the normal range of exit cone angle of a venturimeter ?
7 to 15
The dimension of dynamic viscosity is
ML^-1T^-1
A particle A of diameter 10 microns settles in an oil of specific gravity 0.9 and viscosity 10 poise under Stoke’s law. A particle B with diameter 20 microns settling in the same oil will have a settling velocity
one fourth as that of A.
The pitot static tube does not measure the __________ pressure.
all
The fluid in which the shearing stress within it is proportional to the velocity gradient across the sheared section, is called a __________ fluid.
Newtonion
The ratio of the depth of flow to the hydraulic radius for the most economical trapezoidal section, in open channel flow is
2
The drag co-efficient for a bacterium moving in water at 1 mm/s, will be of the following order of magnitude (assume size of the bacterium to be 1 micron and kinematic viscosity of water to be 10^-6m^2/s).
0.44
For Laminar flow through a packed bed, the pressure drop is proportional to (Vs is the superficial liquid velocity and Dp is the particle diameter)
Vs/Dp^2
The maximum delivery pressure of compressors can be upto __________ atmospheres.
1000
Dimension of surface tension is(where, F = force, L = length)
FL^-1
Which of the following is not a dimension-less parameter ?
None of these
Co-efficient of velocity is __________ the coefficient of discharge.
more than
All pipes of a particular nominal size have the same
outside diameter
For the transfer of solution of thick slurry, the pump used is a __________ pump.
diaphragm
Which of the following is not concerned with the fluid-particle interaction ?
Weber number
Maximum theoretical suction lift for water at 15°C by a centrifugal pump is 34 ft. The same for water at 90°C will be __________ ft.
8
Pressure drag does not depend upon the
all
Dimension of absolute viscosity is
ML^-1T^-1
__________ pumps are axial flow pumps.
Propeller
Brownian movement is prominent in the particle size range of __________ microns in case of settling of a particle in a fluid.
2 to 3
For a particle settling in water at its terminal settling velocity, which of the following is true ?
Weight = buoyancy + drag
A Bingham fluid of viscosity μ = 10 Pa.s and yield stress, τ0 = 10 KPa, is shared between flat parallel plates separated by a distance of 10-3 m. The top plate is moving with a velocity of 1 m/s. The shear stress on the plate is
20 KPa
Pick out the correct statement.
A. A forced vortex occurs when fluid rotates as a solid about an axis.
B. In laminar flow, Newton’s law of viscosity does not apply.
C. A free vortex occurs, when fluidrotates as a solid.
D. In turbulent flow, there are neither cross-currents nor eddies.
A forced vortex occurs when fluid rotates as a solid about an axis.
Shear stress in a fluid flowing in a round pipe
is zero at the centre and varies linearly with the radius.
The resistance wire used in a hot wire anemometer for conducting electrical current is made of
tungsten
Two dimensional stream function
is constant along a stream line.
What causes cavitation in centrifugal pump ?
Low suction pressure
Draining of shallow pits or sump is done by a sump pump, which is a __________ pump.
single stage vertical
A hydraulic ram acts as a/an __________ pump.
impulse
The ratio of average fluid velocity to the maximum velocity in case of laminar flow of a Newtonion fluid in a circular pipe is
0.5
Choose the correct set of dimensions of viscosity that are equivalent (where, F, M, L, T are dimensions for force, mass, length and time respectively).
FL^-2T, ML^-1T^-1
The line of action of the buoyant force passes through the centre of gravity of the
displaced volume of the fluid.
Pick out the wrong statement.
A. The shear stress at the pipe (dia = D, length = L) wall in case of laminar
flow of Newtonion fluids is
B. In the equation, the value of ‘n’ for
pseudoplastic and dilatent fluids are < 1 and >1 respectively.
C. Shear stress for Newtonion fluid is proportional to the rate of shear in the
direction perpendicular to motion.
D. With increase in the Mach number >0.6, the drag co-efficient decreases in
case of compressible fluids.
With increase in the Mach number >0.6, the drag co-efficient decreases in case of compressible fluids.
The friction factor for turbulent flow in a hydraulically smooth pipe
depends only on Reynolds number.
The pressure at a point in a fluid is not the same in all directions, when the fluid is viscous and
moving
What causes convective acceleration in fluid flow ?
Non-uniformity of flow
The Stoke’s stream function applies to the
cases of axial symmetry.
Slugging in a fluidised bed can be avoided by using
shallow beds of solids and proper choice of particle size.
The ratio of width to depth for the most economical rectangular section in open channel flow is
2
The simple pitot tube measures the __________ pressure.
total
Capacity of a hydraulic accumulator is defined in terms of maximum
amount of energy stored.
Three piping networks as shown in the figure are placed horizontally. They are made using identical pipe segments and are subjected to the same pressure drop across them. Assuming no pressure losses at junctions, the flow rates across the three networks are related as Q1 : Q2 : Q3. (1)
0.0430787037037037
Boundary layer separation is characterised by one of the conditions given below, where ‘Re’ is the Reynolds number for the flow. Select the appropriate conditions.
Re»_space;1, decelerating flow
Manometers measure the __________ pressure.
difference in
Which of the following fluid forces are not considered in the Navier-Stoke’s equation?
Turbulent forces
Which of the following may be termed as a variable orifice flowmeter ?
Rotameter
In turbulent flow, a rough pipe has the same friction factor as a smooth pipe
when the roughness projections are much smaller than the thickness of the laminar film.
Air vessel provided in a reciprocating pump
none of these.
Bernoulli’s equation is dependent on the
none of these.
The capacity of an accumulator is the maximum
energy which it can store.
With increase in the temperature, viscosity of a liquid
decreases
Vena-contracta pressure tapping is at a distance __________ from the position of an orificemeter fitted in a pipe of internal diameter ‘d’
0.5 d
The pump impeller and the turbine runner in a hydraulic torque converter
have different diameters.
Reciprocating pumps compared to centrifugal pumps
are not subject to air binding.
The fluid property which matters for fall-ing rain drops to acquire spherical shape is its
surface tension
The simple pitot tube does not measure the
all
Boundary layer separation occurs when the
cross-section of the channel is reduced.
The head loss in turbulent flow in a pipe varies
approximately as the square of the velocity.
For flow through an orifice from a reservoir, the actual velocity at the vena con-tracta is given by
C.V. √2gh
The ratio of the hydraulic radius to the diameter of the channel, for maximum mean velocity of flow in a circular channel, in open channel flow is
0.3
For the free settling of a spherical particle through a fluid, the slope of, CD-log NRe , plot is
-1
A centrifugal pump loses prime after starting. The reason of this trouble may be
all
Venturimeter and orificemeter measures the __________ of the fluid.
average velocity
Surge tanks are provided in high pressure water pipelines to
reduce the water hammer.
Working principle of manometer comprises of balancing a coloumn of liquid against the pressure to be measured. Inclined tube manometer is especially used for the measurement of __________ pressure.
small differential
Isotropic turbulence occurs
where there is no velocity gradient.
The co-efficient of drag and lift for an incompressible fluid depends on the
Reynolds number
Euler’s equation of motion states, that at every point, the
force per unit mass equals acceleration.
Hydraulic intensifier is used for increasing the
intensity of pressure of the liquid.
Which of the following is the ‘Blaussius equation’, relating friction factor to the Reynolds number ?
f = 0.079.Nre^-0.25
Hydrometer measures the specific gravity of liquids based on the principles of buoyancy. Pycnometer is used to measure the specific gravity of
all
Euler’s equation of motion is a statement expressing
conservation of mass.
During ageing of fluid carrying pipes, the
absolute roughness increases linearly with time.
Pick out the wrong statement.
A. The form drag is dependent upon the occurrence of a wake.
B. The shear stress at any given cross-section of a pipe for steady flow
(either laminar or turbulent) varies linearly as the radial distance.
C. An ideal fluid is the one, which has negligible surface tension
and obeys the Newton’s law of viscosity.
D. Existence of the boundary layer in fluid flow is because of viscosity
of the fluid.
An ideal fluid is the one, which has negligible surface tension and obeys the Newton’s law of viscosity.
Mass velocity is independent of temperature & pressure, when the flow is
steady and the cross-section is unchanged.
Very small pressure difference (< 5 mm water coloumn) can be most conveniently measured by a/an __________ manometer.
inclined tube water.
For pipe flows, head is proportional to __________ at constant capacity(where, D = pipe diameter).
1/D^5
The energy equation, (1) (E = internal energy/mass), is applicable to
all compressible fluids.
A differential pressure cell is used for
remote recording of pressure difference.
If more than two branches of pipes are to be connected at the same point, then use a/an
tee
In case of a centrifugal pump, the ratio of total delivered pressure to pressure developed with the impeller is called the __________ efficiency.
manometric
Acceleration head in a reciprocating pump
does not change the work requirement of the pump.
The ratio of inertial forces to elastic forces is called the __________ number.
Mach
Fluid flow at increasing rate through a diverging pipe is an example of __________ flow.
non-steady non-uniform
The temperature in isentropic flow
depends on Mach number only.
A fluid element has a velocity V = -y^2 . xi + 2yx^2 . j. The motion at (x, y) = (l/√2, 1) is
rotational and compressible
Check in a centrifugal pump is
all
Drag force acting on a body does not depend upon the
density of the body.
Centrifugal pump is normally classified on the basis of the
type of casing.
Where does the maximum stress occur in case of laminar flow of incompressible fluid in a closed conduit of diameter ‘d’?
At the wall
In case of isentropic flow, the speed of sound in an ideal gas is proportional to (where, T = absolute temperature )
√T
Applying a pressure drop across a capillary results in a volumetric flow rate ‘Q’ under laminar flow conditions. The flow rate for the same pressure drop, in a capillary of the same length but half the radius is
Q/16
Cd, Cc and Cv are related (for flow through an orifice) as (where, Cd = discharge co-efficient Cc = co-efficient of contraction (1) Cv = co-efficient of velocity (2)
Cd = Cc.Cv
In an incompressible fluid, the density is
not affected with moderate change in temperature & pressure.
Check valves are used
for unidirectional flow.
Velocity distribution for flow between two fixed parallel plates
varies parabolically across the section.
Priming is needed in a __________ pump.
centrifugal
Which of the fluid forces are not considered in the Reynold’s equation of flow ?
Compressibility forces
For ideally incompressible fluid, the Mach number will be
1
A mono pump is a __________ pump.
positive acting rotary
Higher specific speed (200-500) of a centrifugal pump indicates that the pump is of __________ flow type.
axial
The variable required to be known in correlations used for estimating the horse power of a centrifugal gas compressor and hence its cost are P. Inlet pressure Q. Compressor rpm R. Delivery pressure S. Volumetric flow rate at inlet.
P, Q and R
Theoretical head developed by a centrifugal pump does not depend upon the __________ the impeller.
none of these
In case of isentropic flow, the speed of sound in an ideal gas is proportional to (where M = molecular weight of the gas)
1/√M
Boundary layer separation is caused by the
adverse pressure gradient.
With increase in temperature, the vapor pressure of liquids
increases
A mercury (specific gravity = 13.6) manometer connected across an orificemeter fitted in a pipe shows a manometer reading of 2 cms. If the manometer liquid is changed to carbon tetrachloride (specific gravity = 1.6), then for the same flow rate of water the new manometer reading will be __________ cms.
17
The ratio of wall drag to total drag in the Stoke’s law range is
2/3
Rotary vacuum pumps can reduce the absolute pressure to as low as __________ mm Hg.
0.01
A pitched-blade turbine draws __________ a straight blade turbine.
less power than
The most suitable flow measuring device for the fluid flow measurement in a very large diameter pipeline is a
pitot tube
A centrifugal pump is called a turbine pump, if it is having a
vaned diffusion casing.
Remote control valve is a __________ valve.
butterfly
Which of the following quantities are computed by using the hydraulic radius for non-circular ducts ?
Reynold number, relative roughness and head loss.
Centre of pressure in an immersed body is __________ the centre of gravity.
below
The centre of pressure is
a point on the line of action of the resultant force.
Pascal law is not applicable for a/an __________ fluid.
none of these
In a fluidised bed reactor
temperature is more or less uniform.
The flow of a liquid through tapering pipe at a constant rate is an example of __________ flow.
steady non uniform
Pick out the correct statement pertaining to transition/ entrance length in fluid flow.
all
A perfect gas
has constant specific heat.
In a/an __________ , the flow rate of fluids is obtained by measuring the difference between the impact and the static pressure.
pitot tube
During fluid flow, variation of shear stress(τ) with velocity gradientat (dv/dy) constant pressure temperature is shown below in the figure In the above figure, Binghom plastic is represented by the curve .
II
Speed of sound in an ideal gas depends on its
temperature
A centrifugal pump designed for handling water (μ = 1 cp) will deliver __________ when pumping a thicker oil (μ = 30 cp).
less head & capacity
If ‘x’ is the depth of flow in an open channel of large width, then the hydraulic radius is equal to
x
In fluid flow, the boundary layer separation can not occur
none of these.
For a given fluid flow rate, which of the following incurs maximum head loss ?
Orifice meter
Which of the following assumptions enables the Euler’s equation of motion to be integrated ?
The fluid is incompressible.
A fluid whose apparent viscosity increases with shear rate is termed as the __________ fluid.
dilatant
Which of the following is the most common pump for pumping either raw sewage or sludge ?
Reciprocating pump
Transition length for a turbulent fluid entering into a pipe is around __________ times the pipe diameter.
50
For turbulent flow of an incompressible fluid through a pipe, the flow rate Q is proportional to (Δ P)n, where ΔP is the pressure drop. The value of exponent ‘n’ is
< 1
Reciprocating pumps are not able to compete with the centrifugal pump for industrial use, mainly because these pumps have
higher capital &maintenance cost.
Which is the correct relationship for a centrifugal pump ? (where, D = Impeller diameter, inches H = Head developed, ft of liquid pumped N = Speed of pump, rpm)
D = 1840 H^0.5/N
Which of the following pipe bends will incur the largest head loss ?
U-bend
Which is the most efficient and best for measuring very small flow rate of gases ?
Rotameter
When the water is warm, the height to which it can be lifted by a pump
decreases due to reduced vapour pressure.
Pipes having diameter 14 inches or more are designated by their
outside diameter
Viscosity of water at 40°C lies in the range of
0.5 x 10^-3 to 1 x 10^-3 kg/m.s
A centrifugal pump has the following specifications: Power = 4 H.P.; Speed = 800 rpmHead = 8 metresFlow = 1000 litres/minutes.If its speed is halved, the new discharge will be __________ litres/minute.
500
The dimension of kinematic viscosity is
L^2T^-1
A pipe of I.D. 4 m is bifurcated into two pipes of I.D. 2 m each. If the average velocity of water flowing through the main pipe is 5 m/sec, the average velocity through the bifurcated pipes is
10 m/sec
Turbulent flow generally occurs for cases involving
none of these
Lower BWG means __________ of the tube.
lower cross-section
For laminar flow of Newtonion fluid in a circular pipe, the velocity distribution is a function of the distance ‘d’ measured from the centre line of the pipe, and it follows a __________ relationship.
parabolic
The Prandtl mixing length is
useful for computing laminar flow problems.
N^2Re/NFr is called the __________ number.
Galileo
The location of centre of pressure, which defines the point of application of the total pressure force on the surface, can be calculated by applying the principle of moments according to which “sum of the moment of the resultant force about an axis is equal to the sum of the components about the same axis”. The centre of pressure of a rectangular surface (of width ‘w’) immersed vertically in a static mass of fluid is at a depth of(where, y = depth of the liquid)
2y/3
As the velocity V and thus the Reynolds number of a flow past a sphere increases from very low value, the drag force for Re «_space; 1
increases linearly with V.
Self-priming centrifugal pump can be used for
all
Water hammer is caused, when water flowing in a pipe is suddenly brought to rest by closing the valve. The extent of pressure thus produced due to water hammer depends on the
all
Bernoull’s equation does not apply to the functioning of a/an
none of these
What is the shear rate at the pipe wall, in case of laminar flow of Newtonion fluids in a pipe of diameter ‘D’ & length ‘L’ incurring a pressure drop ‘Δp’ with average velocity ‘Vavg’?
8 . Vavg/D
Pascal’s law is valid, only when the fluid is
at rest.
A centrifugal pump is used to pump water through a horizontal distance of 150 m, and then raised to an overhead tank 10 m above. The pipe is smooth with an I.D of 50 mm. What head (m of water) must the pump generate at its exit (E) to deliver water at a flow rate of 0.001 m^3/s? The Fanning friction factor, f is 0.0062.
11 m
The pressure head of a flow meter remains constant for
rotameter
A venturimeter can not be used for the direct measurement of
all
A double acting reciprocating pump compared to a single acting pump (of almost same size working under same pressure levels) would give almost double
discharge
Which of the following is used for very accurate measurement of flow of gas at low velocity ?
Hot wire annemometer
In Newton’s law range, the drag co-efficient for the motion of spherical particle in a stationary fluid is
0.44
A pressure of 10 m head of water is equivalent to __________ kN/m2.
98
A pressure head of 320 metres of water in meters of CCl4 (sp.gr = 1.6) will be
200
The ratio of the wall drag to the form drag in the Stoke’s law range (for motion of spherical particles in a stationary fluid) is
2
For turbulent flow in smooth circular pipe, the velocity distribution is a function of the distance ‘d’ measured from the wall of the pipe and the friction velocity ‘v’, and it follows a __________ relationship.
logarithmic
Maintenance cost of a __________ pump for a particular duty is the least.
centrifugal
Choking in case of pipe flow means that a
specified mass flow rate can not be achieved.
Velocity of liquid hydrocarbon fuels in a pipeline can not be measured by magnetic flowmeters, because their __________ is very low/small.
electrical conductivity
The nominal size of a hose pipe is specified by its
I.D.
Transition from laminar flow to turbulent flow is aided by the
all
For flow of fluids through packed bed, the superficial velocity is
less than the average velocity through channels.
Cd is always __________ Cc.
greater than
Buoyant force
depends on the weight of the floating body.
Which of the following is an undesirable property of a manometric liquid ?
High vapour pressure.
Characteristic curves for a centrifugal pump plotted against its capacity is shown in the diagram. x, y and z denote respectively (1)
head, efficiency and B.H.P.
Liquid delivery by centrifugal pump starts, only when the head developed by it is equal to the __________ head.
manometric
The speed of sound in an ideal gas varies as the
temperature
The maximum head that can be developed by a single impeller is __________ ft.
250-300
The ratio of hydrodynamic boundary layer to thermal boundary layer thickness in case of liquid metals is
< 1
The general relationship between speed N, head H, power P and discharge Q for a centrifugal pump is
Q∝N : H∝N^2 : P∝N^3
What is the ratio of the velocity at the axis of the pipe to the mean velocity of flow in case of pipe flow under viscous condition ?
2
Foot valve provided in the pump is a __________ valve.
back pressure
The discharge co-efficient for an orificemeter does not depend upon the
pipe length.
Which of the following options will facilitate the achievement of a very high head (say 30 metres) in case of a centrifugal pump?
Mounting of two or more impellers in series on a single shaft.
An equipotential line is __________ to the velocity vector at every point.
normal
Path followed by water jet issuing from the bottom of a water tank will be a
parabola (vertex being at the opening).
Which of the following produces maximum pressure difference for transportation of gases ?
Compressors
For flow through a venturi at a particular discharge, the correct relationships among velocities at point X, Y and Z would be (1)
V2 > V1 and V2 > V3
Drag co-efficient in hindered settling is __________ that in free settling.
always greater than
Efficiency of power transmission (η) through a circular pipe is given by (ht - hf)/ht, which has a maximum value of __________ percent.
66.6
One dimensional fluid flow implies the
flow in which transverse components are zero.
__________ forces act on a particle moving through a stationary fluid.
all
In frictional fluid flow, the quantity, (1) , is
not constant along a streamline.
Hydraulic radius is the ratio of
flow area to wetted perimeter.
The unit of bulk modulus of elasticity for a liquid in S.I. unit is
N/m^2
Power requirement of fans having constant wheel diameter varies __________ fan speed.
as cube of
In the low Reynolds number region, the drag force on a sphere is proportional to
V
The continuity equation
represents the conservation of mass.
Experimental study of laminar fluid flow through a circular tube was conducted by
Hagen and Poiseuille
The most economical flow control valve for use with large diameter pipes is a
butterfly valve
Each term in Bernaulli’s equation represents the __________ of the fluid.
energy per unit weight
Which of the following is a dimensionless parameter ?
None of these
If the head over the triangular notch is doubled, the discharge will increase by __________ times.
5.657
Friction factor for a hydraulically smooth pipe at NRe = 2100 is f1. If the pipe is further smoothened (i.e., roughness is reduced), the friction factor at the same value of NRe, will
increase.
For the laminar flow of a fluid in a circular pipe of radius R, the Hagen-Poisseule equation predicts the volumetric flow rate to be proportional to
R^4
Interstage coolers are provided in a multistage compressor to
save power in compressing a given volume to a given pressure.
Consider a centrifugal pump having a specific impeller diameter, fixed impeller speed pumping a liquid of constant density at a particular discharge capacity. With decrease in the capacity of the pump, the __________ decreases.
all
Reynolds number is the ratio of
inertial forces to viscous forces.
For the manometer set up shown in the figure, the pressure difference PA - PB is given by (1)
(ρH - ρair)gH
The discharge through a venturimeter depends upon
pressure drop only.
N. second/m^2 is
the S.I. unit of dynamic viscosity.
The distance between metacentre and __________ is called metacentric height.
centre of gravity
Check valve is used for __________ flow.
unidirectional
Capacity of a rotary gear pump can be varied by
all
For a given Reynolds number, in a hydraulically smooth pipe, further smoothening __________ the friction factor.
brings about no further reduction of
Power number is the ratio of
drag stress to inertial stress.
The momentum correction factor for the velocity distribution of laminar flow is
none of these
For the same flow rate of a fluid, the pressure drop is the least for
venturimeter
The valve commonly used in pipes larger than 2” dia is a
gate valve
Foot valves are provided in the suction line of a centrifugal pump to
avoid priming, every time we start the pump.
An ideal fluid is
frictionless & incompressible.
In area meter (e.g., rotameter), with increase in the fluid flow rate, the
pressure drop is almost constant.
In power law, (1) , then the fluid is
Newtonian
The buoyant force acting on a floating body is dependent on the
weight of the liquid displaced.
A Newtonion fluid is that
for which shear & deformation are related as (1)
In case of end to end connection of two or more pipes in series, the __________ each pipe.
same rate of flow passes through
Which of the following equations applies to the fluid flow through a packed bed for very large Reynolds number ?
Blake-Pllummer equation
The flow of gas along a pipe in the direction of decreasing pressure causes decrease in its
specific volume
Centrifugal pump can’t be used to pump
thick molten soap at 80°C.
A stream line is
fixed in space in steady flow.
Quicksand is an example of a __________ fluid.
dilatent
Correction for capillary effect in manometers (used for pressure measurement) need not be applied, if diameter of the manometer tube is __________ mm.
> 12.5
Differential manometer measures the
pressure difference
The pressure and power requirement of a gas fan at constant speed & capacity varies __________ the gas density.
directly as
Boundary layer thickness in laminar flow over a flat plate increases as(where, d = distance from the leading edge.)
√d
Gradually varied flow in open channel is a/an __________ flow.
steady non-uniform
The line of action of the buoyant force acts through the
centroid of the displaced volume of fluid.
Cavitation in a centrifugal pump can be avoided by keeping the
inlet pressure high
Vane anemometer
rotates an element at a speed determined by the velocity of the fluid in which the meter is immersed.
The peripherial velocity at inlet of a centrifugal pump having inlet diameter of 25 cms and rotating at 950 rpm is __________ m/sec.
12.4
Laminar flow is characterised by the nonexistence of
all
The length of the tube necessary for the boundary layer to reach the centre of the tube and for fully developed flow to be established is called the __________ length.
transition
Select the correct practical example of steady non-uniform flow.
Steadily decreasing flow through a reducing section.
Hydraulic diameter for non-circular ducts is equal to __________ times the area of flow divided by the perimeter.
four
Terminal velocity is
a constant velocity with no acceleration.
Consider two pipes of same length and diameter through which water is passed at the same velocity. The friction factor for rough pipe is f1 and that for smooth pipe is f2. Pick out the correct statement.
f1 > f2
For an incompressible fluid, the bulk modulus of elasticity is
∞ N/m^2
A fluid is a substance, that
flows when even a small shear is applied to it.
The pressure intensity is the same in all directions at a point in a fluid
when there is no motion of one fluid layer relative to an adjacent layer.
Which of the following must be followed by the flow of a fluid (real or ideal)? (I) Newton’s law of viscosity. (II) Newton’s second law of motion. (III) The continuity equation. (IV) Velocity of boundary layer must be zero relative to boundary. (V) Fluid cannot penetrate a boundary.
II, III, V
Mach number is defined as the ratio of the local flow velocity to the sonic velocity in the fluid. For what value of Mach number, the gases are considered incompressible ?
< 0.3
Boundary layer exists in flow
of real fluids.
Rubber latex is an example of __________ fluid.
pseudoplastic
The frictional resistance in laminar flow does not depend on the
area of surface in contact.
A venturimeter measures the
none of these
Gradually varying fluid flow is an example of __________ flow.
non-steady uniform
Drag is the force component exerted on an immersed object,
the component being parallel to theflow direction.
To handle smaller quantity of fluid at higher discharge pressure, use a __________ pump.
reciprocating
Cocks are used to control
any liquid
The dimension of surface tension is
MT^-2
Pick out the correct statement.
a. Fanning friction factor is inversely proportional to Reynolds number
always.
b. The property of a randomly packed bed (with raschig rings) is given
by the ratio of the total volume to the volume of voids in the bed.
c. Mach number in an incompressible fluid is always unity.
d. Mach number is given by the ratio of the speed of the fluid to
that of sound in the fluid under conditions of flow.
Mach number is given by the ratio of the speed of the fluid to that of sound in the fluid under conditions of flow.
The friction factor is
none of these.
Rubber latex is an example of a __________ .fluid.
pseudoplastic
Which of the following factors does not contribute to the pressure drop in a pipeline ?
None of these
The phenomenon occuring during pumping of a liquid solution containing dissolved gases, which may come out of the solution giving rise to gas pockets, is termed as
cavitation
Working of a __________ pump characterises mixed flow.
turbine
The rate of change of moment of momentum represents the __________ by the fluid.
torque applied
Cd for the orifice plate varies from
0.58 to 0.8
The discharge through a V-notch weir varies as
H^5/2
Water flow rate in a pipe of 3.5 metres diameter can be most economically and conveniently measured by a/an
pitot tube
The specific speed of a pump is defined as the speed of a unit of such a size, that it
delivers unit discharge at unit head.
In case of venturimeters, friction losses are about __________ percent of maximum velocity head.
2
With increase in the schedule number of a pipe of a particular nominal size, the
all
Turbine impeller
is effective over wide range of viscosities.
Friction produced by the formation of wakes is called the __________ friction.
form
Various efficiencies of a centrifugal pump are related as (where, ηm = mechanical efficiency ηv = volumetric efficiency. ηma = manometric efficiency ηo = overall efficiency)
ηm = ηv . ηma
When the pipe Reynold’s number is 6000, the flow is generally
turbulent
With a constant diameter impeller of a centrifugal pump
head varies as the square of speed.
For water, when the pressure increases, the viscosity
first decreases, and then increases
Location of vena-contracta in an orificemeter does not depend upon the
type of orifice.
At low Reynolds number
viscous forces control and inertial forces are unimportant.
For laminar flow through a closed conduit
Vmax = 2Vav
In Newton’s law range, the terminal velocity of a solid spherical particle falling through a stationary fluid mass varies as the __________ of its diameter.
square root
Unsteady uniform flow is represented by flow through a/an
long pipe at decreasing rate.
If Blausius or Darcey friction factor is ‘f1’ then the Fanning friction factor is equal to
f1/4
Pick out the wrong statement pertaining to fluid flow.
The ratio of average velocity to the maximum velocity for turbulent flow of Newtonion fluid in circular pipes is 0.5.
A Newtonion liquid (ρ = density, μ = viscosity) is flowing with velocity v in a tube of diameter ‘D’. Let Δp be the pressure drop across the length ‘L’. For a laminar flow, Δp is proportional to
L ρv2/D
While starting a centrifugal pump, its delivery valve should be kept
closed.
For flow past a flat plate, if x is the distance along the plate in the direction of flow, the boundary layer thickness is proportional to
x
Sewage sludge is an example of the __________ fluid.
Bingham plastic
Multistage centrifugal pumps are generally used for
high head.
The fluid jet discharging from a 2” diameter orifice has a diameter of 1.75” at its vena-contracta. The co-efficient of contraction is
0.766
A bed consists of particles of density 2000 kg/m^3. If the height of the bed is 1.5 metres and its porosity 0.6, the pressure drop required to fluidise the bed by air is
11.77 kPa
Cavitation in a pump creates so many undesirable effects. Out of the following, which is not an undesirable effect created by cavitation ?
Develops high pressure
For a specific centrifugal air blower operating at constant speed & capacity, the power requirement and pressure vary
directly as gas density.
Capillary tube method of viscosity measurement is based on the
Hagen-Poiseulle’s equation
It is possible to integrate an automatic flow controller to a
rotameter
For liquid flow through a packed bed, the superficial velocity as compared to average velocity through the channel in the bed is
less
For a reciprocating pump, the indicator diagram is the graph between the
volume swept by piston for one complete revolution and the pressure in the cylinder.
High specific speed of a pump implies that, it is a/an __________ pump.
axial flow
A gas (density = 1.5 kg/m^3 , viscosity = 2x 10^-5 kg/m.s) flowing through a packed bed (particle size = 0.5 cm, porosity = 0.5) at a superficial velocity of 2 m/s causes a pressure drop of 8400 Pa/m. The pressure drop for another gas, with density of 1.5kg/m^3and viscosity of 3 x 10^-5kg/m.s flowing at 3 m/s will be
12600 Pa/m
One poise (unit of absolute/dynamic viscosity) is equivalent to one
gm/cm. sec.
The equation relating friction factor to Reynold number, f^-0.5 = 4 loge (NRe/f)^-0.4, is called the __________ equation.
Nikuradse
What is the co-efficient of contraction, if a fluid jet discharging from a 50 mm diameter orifice has a 40 mm diameter at its vena-contracta ?
0.64
For an unstable equilibrium of a floating body (where, M = metacentre.)
M is below G
Which of the following can be used for the direct measurement of volumetric flow rate of slurry ?
Rotameter
A pipe is defined as ‘hydraulically smooth’, if the friction factor
for a given Reynolds number remains constant even on further smoothening of the pipe.
A Pitot tube indicates 5 cm of water (manometer) when it is being used for measuring velocity of air. The velocity of air in m/sec is
28.2
Delivery of insufficient quantity of liquid by a pump may be caused by
all
In case of a __________ the energy of flow is considerably decreased downstream of the machine.
turbine
With increase in the shear rate, the apparent viscosity of pseudoplastic fluids
decreases
Co-efficient of discharge (Cd) is defined as actual discharge/theoretical discharge and is equal to Cc . Cv; where Cc = Co-efficient of contraction and Cv = co-efficient of velocity. Cd of an orifice is usually about
0.62
Purpose of hydraulic accumulator is to
generate high pressure to operate hydraulic machines like cranes, lifts, presses etc
Pick out the wrong statement.
a. Surface tension of a liquid is because of the difference in magnitude
of adhesive & cohesive forces.
b. A hydrometer used for the determination of specific gravities of
liquids works on the principle of buoyant forces.
c. In case of unsteady fluid flow, the velocity at any given point
does not change with time.
d. Turbulent fluid flow is characterised by the rapid fluctuation of
instantaneous pressure & velocity at a point.
In case of unsteady fluid flow, the velocity at any given point does not change with time.
Purpose of relief valve in a reciprocating pump is to
protect the pump against developing excessive pressure.
Select the correct statement.
The discharge through a venturimeter depends upon Δp only and is independent of orientation of the meter.
In case of turbulent flow of fluid through a circular pipe, the
skin friction drag, shear stresses, random orientation of fluid particles and slope of velocity profile at the wall are more.
What is the maximum theoretical suction lift (metres) of a reciprocating pump ?
10
The terminal velocity of a particle moving through a fluid varies as dp^n. The value of n is equal to __________ in Stoke’s law regime.
2
Function of air vessel provided in a reciprocating pump is to
reduce discharge fluctuation.
The Prandtl pitot tube measures the
velocity at a point in the flow.
Pressure drop in packed bed for turbulent flow is given by the __________ equation.
Blake-Plummer
In the complete turbulence zone (in rough pipes), the
friction factor is independent of the relative roughness.
Which of the following has the minimum compressibility ?
Water at room temperature
In case of centrifugal fan or blower, the gas capacity varies as
speed
Pick out the wrong statement.
a. Surface tension of a liquid is because of the difference in magnitude
of adhesive & cohesive forces.
b. A hydrometer used for the determination of specific gravities of
liquids works on the principle of buoyant forces.
c. In case of unsteady fluid flow, the velocity at any given point
does not change with time.
d. Turbulent fluid flow is characterised by the rapid fluctuation of
instantaneous pressure & velocity at a point.
Newton’s law of viscosity is not applicable to the turbulent flow of fluid with linear velocity distribution.
Pick out the wrong statement.
a. In a static mass of liquid, the pressure at a point is the same for
all liquids.
b. Pressure decreases exponentially with elevation in an isothermal
atmosphere.
c. Atmospheric pressure = absolute pressure-gage pressure.
d. As per Pascal’s law, the pressure at a point in a static or uniformly
moving fluid is equal in all directions.
In a static mass of liquid, the pressure at a point is the same for all liquids.
The velocity profile for a Bingham plastic fluid flowing (under laminar conditions) in a pipe is
parabolic near the wall and flat in the middle.
Mach number is the ratio of the speed of the
fluid to that of the sound.
A piezometer opening measures the __________ fluid pressure.
undisturbed
Drag force on the float of a rotameter is(where Q = flow rate of the )
constant
The unit of dynamic viscosity in SI unit is
kg/m . sec
Pressure drop (Δp) for a fluid flowing in turbulent flow through a pipe is a function of velocity (V) as
V^2
Dean number is concerned with the
fluid flow through helical pipes.
The equation given below is called the __________ .
F^-0.5 = 4.07 loge (NRe√f)^-0.6
Von-Karman equation
Poise is converted into stoke by
dividing by density (gm/c.c).
The fluid velocity varies as the square root of the cylindrical pipe diameter in case of steady state laminar flow at constant pressure drop fo __________ fluid.
dilatant
Kinetic energy of fluid per unit weight represented by the velocity head is given by
v^2/2gc
At a constant speed of the centrifugal pump . it __________ the impeller diameter.
all of these
The pressure co-efficient is the ratio of pressure forces to __________ forces.
viscous
Vena-contracta formed during flow of a liquid through an orificemeter has
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, μ = fluid viscosity)
μ
Horsepower increase of a centrifugal gas compressor without altering the volumetric flow rate will __________ the gas discharge pressure.
increase
In continuous fluidisation
solids are completely entrained.
Glass pipes can be joined by
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
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
Weber number is the ratio of inertial force to __________ force.
surface tension
The curve of metacentre for a floating body __________ the curve of buoyancy.
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°
The range of a particular rotameter can be increased by
use of floats of different densities.
Which of the following is dimensionless ?
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.
660
A compressor that takes suction at a pressure below atmospheric and discharge against atmospheric pressure is called a __________ pump.
vacuum
A bed of spherical particles (specific gravity 2.5) of uniform size 1500 μm 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 : Δ 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 ?
0.7
Dimension of kinematic viscosity is
L^2 . T^-1
A streamline is a line in flow field,
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
closed
__________ forces do not act in case of fluid flow.
Tensile
Non-colloidal solution is an example of the __________ fluid.
Newtonion
Boundary layer separation is caused by the
adverse pressure gradient.
Identification of pipelines carrying different liquids and gases is done by the __________ of the pipe.
colour
Pick out the correct statement.
a. Human blood is a Newtonion fluid.
b. A Newtonion fluid obeys Newton’s law of cooling.
c. For a non-Newtonion fluid, a straight line passes through the origin
in a plot between shear stress and shear gradient.
d. 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
Hydraulic __________ works on the principle of Pascal’s law of transmission of fluid pressure.
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
The contraction co-efficient for Borda’s mouthpiece (for frictionless fluid) is
0.5
Purpose of air lift pump is to
lift water from a well by using compressed air.
Pick out the correct statement pertaining to venturimeter.
none of these.
For very low pressure and high discharge rate, the compressor used is a/an __________ compressor.
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.
gear
What is the speed of sound (m/sec) in ordinary water ?
1500
Two piping system are said to be equivalent, when the __________ are same.
fluid flow rate & friction loss
Potential function is applicable only for __________ flow.
irrotational
Which of the following exemplifies a three dimensional fluid flow ?
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.
The head loss due to sudden contraction is proportional to
velocity head
Cavitation occurs in a centrifugal pump when the suction pressure is
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
The capacity of a centrifugal pump Can be increased by increasing the
all
Which law is followed by the velocity distribution in the turbulent boundary layer?
Logarithmic law
The losses in open channel flow generally vary as the
first power of the roughness.
Out of the following flow measuring devices, which one incurs the maximum installation cost as well as pressure loss ?
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
Which of the following has the maximum compression ratio ?
Vacuum pump
Scale up of agitator design requires
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
The head loss in turbulent flow in pipe is proportional to(where, V = velocity of fluid through the pipe)
V^2
Unsteady non-uniform flow is represented by flow through a/an
expanding tube at increasing rate.
Prandtl number is a measure of the
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
In hindered settling, the particles are
near each other,
A globe valve is the most suitable for applications, in which
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.
Pitot tube
One stoke (unit of kinematic viscosity) is equivalent to
1 cm^2/second
Air vessel of a reciprocating pump is initially filled with
compressed air
The ratio of inertial forces to gravity forces is called the __________ number.
Froude
Power required by a centrifugal pump is proportional to (where, D = diameter, N = r.p.m)
N^3D^5
Equivalent length of a pipe fitting is
dependent on Reynolds number.
Buckingham-π theorem states that in any physical problem including ‘n’ quantities having ‘m’ diamensions, the quantities can be arranged into __________ independent dimensionless parameters.
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
Existence of boundary layer in fluid flow is because of the
fluid viscosity
In case of laminar flow of fluid through a circular pipe, the
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 ?
Globe valve
For an ideal fluid flow, Reynolds number is
0
Stoke’s equation is valid in the Reynolds number range
0.01 to 0.1
When a fluid flows over a solid surface, the
velocity gradient is zero at the solid surface.
Pick out the wrong statement about cavitation.
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.
4000
The velocity for subsonic flow in a pipeline
increases in the downstream direction.
Permanent pressure loss in a well designed venturimeter is about __________ percent of the venturi differential.
10
The ratio of pressure forces to inertial forces is called the __________ number.
Euler
Bernoulli’s equation for fluid flow is derived following certain assumptions. Out of the assumptions listed below, which set of assumptions is used in derivation of Bernoulli’s equation ?A. Fluid flow is frictionless & irrotational. B. Fluid flow is steady. C. Fluid flow is uniform & turbulent.D. Fluid is compressible.E. Fluid is incompressible.
A, B, E
Cavitation in a centrifugal pump results from
low barometric pressure
For turbulent flow of newtonion fluid in a circular cross-section pipe, the ratio of maximum to average fluid velocity is
1
For flow through a venturi at a particular discharge, the correct relationships among heads at points X, Y, and Z are (1)
h1 > h2 < h3
Water is flowing at 1 m/sec through a pipe (of 10 cm I.D) with a right angle bend. The force in Newtons exerted on the bend by water is
5π/2
The time of oscillation of a floating body is
none of these.
What is the value of Fanning friction factor f ‘ for smooth pipe at NRe = 106 approximately ?
0.003
Air vessel provided in a reciprocating pump is for
making the friction in pipe uniform.
A hydraulic accumulator comprises of
a cylinder and a plunger.
Bernoulli’s equation for steady, frictionless, continuous flow states that the __________ at all sections is same.
total energy
A tube is specified by its
thickness & outer diameter both
Prandtl mixing length is
zero at the pipe wall.
The hydraulic diameter of an annulus of inner and outer radii Ri and Ro respectively is
2(Ro-Ri)
Ratio of inertial forces to surface tension forces is called the __________ number.
Weber
In open channel flow in a rectangular channel, the ratio between the critical depth and the initial depth, when a hydraulic jump occurs is
1.84
The ratio of inertial forces to viscous forces is called the __________ number.
Reynold
Enamels and paints are generally __________ fluid.
pseudo-plastic
With the increase in depth, the hydrostatic pressure in an unaccelerated incompressible fluid (in a constant gravitational field)
increases linearly.
Flow measurement in an open channel is done by a/an
weir
Newton’s law of viscosity relates the
shear stress and rate of angular deformation in a fluid.
The equivalent diameter for fluid flow through square cross section channel of side ‘x’, for pressure drop calculation purpose is given by
x
Hydraulic radius of 6” x 12” cross-section, is __________ inches.
2
Baffles in mixing tanks are provided to
reduce swirling and vortex formation.
Which of the following equations is valid for laminar flow of a fluid through packed bed?
Kozney - Karman equation
Forces acting on a particle settling in fluid are __________ forces.
gravitational or centrifugal buoyant drag.
For a fluid rotating at constant angular velocity about vertical axis as a rigid body, the pressure intensity varies as the
square of the radial distance.
In a dry packed bed, the pressure drop will be changed by increasing the flow rate as
V^1.8
Specific speed of a centrifugal pump depends upon the __________ head.
none of these
Navier-Stokes equation is useful in the analysis of __________ fluid flow problems.
viscous
The maximum discharge through a circular channel takes place, when the depth of the fluid flow is __________ times the pipe diameter.
0.95
When the head pumped against is less than the head of the fluid used for pumping, the usual device is a/an
airlift
Two fluids are flowing through two similar pipes of the same diameter. The Reynold’s number is same. For the same flow rate if the viscosity of a fluid is reduced to half the value of the first fluid, the pressure drop will
decrease
What is the value of co-efficient of discharge for square edged circular orifice (for β = 0.3 to 0.5) ?
0.61 - 0.63
A lubricant 100 times more viscous than water would have a viscosity (in Pa.s)
0.1
Nominal Pipe Size (NPS) of a pipe less than 12 inches in diameter indicates its
neither inner nor outer diameter
I.D. of 1/4” schedule 40 pipe is 0.364”. I.D. of a 1/2” schedule 40 pipe would be __________ inch
0.5
Two liquids manometer is used for measuring small pressure differences in
gases
A piezometer provided in the pipe measures
static pressure
The pump used for irrigation purposes is generally designed for
large capacity & low head.
In centrifugal pumps, cavitation occurs, when pressure of the impeller eye or vane becomes
less than liquid vapor pressure.
Pressure gradient in the pipe flow is influenced by the
all
__________ pump is the most suitable device for discharging a liquid against a pressure of ≥ 1500 kgf/cm2.
Plunger
Boiler feed water pump is usually a __________ pump.
multistage centrifugal
Viscosity of a liquid decreases __________ with rise in temperature.
logarithmically
In case of a pipe of constant cross-sectional area, the maximum fluid velocity obtainable is
the velocity of sound.
Discharge in laminar flow through a pipe varies
as the square of the radius.
The lift of a ballon is
due to the weight of the atmospheric air, that it displaces.
In which of the following body shapes, the pressure drag is large compared to the friction drag ?
Bluff body
Major loss in sudden contraction in pipe flow is due to
flow contraction.
Which of the following can be used to create a flow of gas, where no significant compression is required ?
Blower
The ratio of actual discharge to theoretical discharge through an orifice is equal to
Cc . Cv
A free jet of water of cross-sectional area 0.01m^2 and a velocity of 20 m/s strikes a plate and then flows in a plane parallel to the plate as shown in the figure below. The horizontal component of the force on the support is
4000 N
Cp/Cv is termed as
adiabatic constant
Which of the following is a Newtonian fluid?
Non-colloidal solution
Which of the following valves will incur maximum pressure drop for the same discharge of water ?
Needle valve
Pressure drop in a fluidised bed reactor is __________ that in a similar packed bed reactor.
more than
In deriving Bernoulli’s equation, fluid is assumed to be
incompressible, frictionless, steady, along a streamline.
Unit of mass velocity is
kg/m^2. hr
With increase in molecular weight of the gas, the head developed by a centrifugal compressor will
decrease
Pressure difference between two points in vessels, pipelines or in two different pipelines can be measured by a differential manometer. The pressure difference measured as the mm of water coloumn in case of mercury-water, differential manometer is equal to (where, H = difference in height of mercury column in mm).
12.6 H
The boundary layer thickness at a given section along a flat plate __________ with increasing Reynold’s number.
decreases
Low specific speed of a pump implies that, it is a/an __________ pump.
centrifugal
For pumping slurry, one can use a __________ pump.
diaphargm
Bernoulli’s equation describes the
mechanical energy balance in potential flow.
Which law/principle of solid mechanics is similar/equivalent to Newton’s law of viscosity in fluid mechanics ?
Hooke’s law.
When larger particles e.g., grains are subjected to fluidisation, the corresponding bed produced is termed as the __________ bed.
spouted
Minimum fluidisation velocity for a specific system depends upon the
all
Potential flow is characterised by the
irrotational and frictionless flow.
For the production of very high vacuum, a __________ pump is normally used.
diffusion
In parallel pipe problems, the
head loss is the same through each pipe.
Fluid flow through a packed bed is represented by the __________ equation.
Ergun’s
__________ is an example of axial flow impeller.
Propeller
Froude number is not a factor
when there is no vortex formation.
If three pipes of different diameters, lengths & friction factors are connected in parallel, then (where, Q = flow rate, V= fluid velocity f = friction factor).
Q = Q1 + Q2 + Q3
Horsepower requirement for given pump capacity depends upon the
all
Bernoulli’s equation accounts for the
different forms of mechanical energy
__________ pumps are a group of vacuum pumps.
Hyter
Plunger pumps are used for
higher pressure
What is the ratio of displacement thickness to nominal thickness for a linear distribution of velocity in the boundary layer on a flat plate ?
0.5
In turbulent flow, the
shear stresses are generally larger than in a similar laminar flow.
Momentum correction factor used in fluid flow problems accounts for the
non uniform direction of velocities at inlet & outlet sections.
Design of the casing of centrifugal pump should be such as to minimise the
loss of kinetic head
Which of the following is used for pumping crude oil from oil well ?
Duplex/triplex reciprocating pump
The energy loss in flow through ven-turimeter is less than that through flow nozzle, because in case of a flow nozzle, the
sudden expansion of flow in the downstream occurs.
__________ flow means the flow of incompressible fluid with no shear.
Potential
The continuity equation
relates mass flow rate along a stream tube.
The energy loss over a length of pipeline according to Darcy-Weisbach equation for pipe flow is…..the mean velocity of flow.
directly proportional to square of
Pressure drop in a packed bed for laminar flow is given by the __________ equation.
Kozney-Karman
The fluid velocity varies as the cube of the cylinderical pipe diameter in case of steady state laminar flow at constant pressure drop for __________ fluid.
pseudoplastic
Stoke’s law is valid, when NRe, p is less than
2
Froude number is the ratio of
inertial stress to gravitational stress.
Normal depth in open channel flow is the depth of flow in the channel
corresponding to uniform flow.
Which of the following flow measuring devices is an area meter ?
Rotameter
With decrease in particle size to be fluidised by a particular fluid, the operating range of fluidisation velocity
does not change
Diaphragm valves are used for handling __________ fluids.
corrosive
The schedule number of a pipe is an indication of its
wall thickness
Minimum porosity for fluidisation is
the porosity of the bed when true fluidisation begins.
A centrifugal pump used to pump water is used to pump an oil with specific gravity of 0.8 at the same rate. The power consumption will now
decrease
Steady non-uniform flow is exemplified by flow through a/an
expanding tube at constant rate.
The maximum depth from which a centrifugal pump can draw water is
34 feet.
Hot wire anemometer is used to measure the
velocity of gases.
Propeller type centrifugal pumps are most suitable for
high capacity at low heads.
The fluid velocity varies as the square of the cylindrical pipe diameter, in case of steady state laminar flow at constant pressure drop, for __________ fluid.
Newtonion
Momentum transfer in laminar flow of fluids results due to the
velocity gradient
The capillary rise of mercury is maximum in glass tube of dia __________ mm.
0.5
Diaphragm pumps are used to transport
slurries
For steady ideal fluid flow, the Bernoulli’s equation states that the
energy is constant along a stream line, but may vary across stream lines
In case of a centrifugal pump, the theoretical head developed is dependent on the __________ the impeller.
all
A hydraulic press has a ram of 10 cms in diameter and a plunger of 1 cm in diameter. The force required on the plunger to raise a weight of 10 tons on the ram is __________ kg.
100
Choose the set of pressure intensities that are equivalent.
4.33 psi, 10 ft. of water, 8.83 inches of Hg.
Pick out the wrong statement about a streamline.
It is always parallel to the main direction of the fluid flow.
The most serious disadvantage of an orificemeter is that
most of the pressure drop is not recoverable.
The discharge through a rectangular weir varies as
H^3/2
In case of supersonic flow of a fluid through pipeline, the ‘Mach number’ is
> 1
A centrifugal pump has the following specifications: Power = 4 H.P.; Speed = 800 rpmHead = 8 metresFlow = 1000 litres/minutes.If its speed is halved, the power consumed now will be __________ hp.
0.5
Transition length for turbulent flow in smooth pipe is equal to __________ times the pipe diameter.
50
Disc compensators are provided in large diameter fuel gas carrying pipelines to
account for contraction/expansion of pipe due to temperature changes of the surroundings.
Discharge from a 24 inch pipe of water at 10 ft/sec will be __________ ft3/sec.
125.6
Paper pulp is an example of __________ fluid.
bingham plastic
The ratio of the depth of flow to the diameter of the channel for maximum discharge in a circular channel in open channel flow is
0.95
A conical tank with a bottom opening of cross-sectional area A is filled with water and is mounted on supports as shown in the figure. What is the force F with which plate X must be pushed up to prevent water from leaking ? Assume that the density of air is negligible as compared to the density of water ρL. (1)
ρL . A.Hg
A relief valve
is a directional control valve.
An isentropic process is the one, in which
pvr = constant, and process is reversible
The distribution of shear stress in a stream of fluid in a circular tube is
linear with radius for both laminar & turbulent flow.
For motion of spherical particles in a stationary fluid, the drag co-efficient in hindered settling compared to that in free settling is
more
Specific speed of a centrifugal pump relates it with another pump having the
dynamic similarity
Air vessel fitted to a reciprocating pump
decreases the work done.
Deformation drag, which is caused by widespread deformation of fluid around the immersed body
occurs when NRe is very small.
In isotropic turbulence, the __________ are equal to each other.
mean square of velocity fluctuations in the three co-ordinate directions
Viscosity of water is about __________ times that of air at room temperature.
55
Net positive suction head (NPSH) of a centrifugal pump must be
greater than the vapour pressure of the liquid.
Actual lift of a pump is always less than the theoretical lift and is limited by the
all
In case of unsteady fluid flow, conditions & flow pattern change with the passage of time at a position in a flow situation. Which of the following is an example of unsteady flow?
Water flow in the suction and discharge pipe of a reciprocating pump.
Nature of fluid flow during the opening of a valve in a pipeline is
unsteady
The __________ pressure is measured by a static tube.
static
The speed of a sound wave in a gas is analogous to the speed of
an elementary wave in an open channel.
Mercury is an ideal barometric fluid mainly due to its
very low vapor pressure.
A spherical particle is falling slow in a viscous liquid such that Reynolds number is less than 1. Which statement is correct for this situation ?
Drag, gravitational and buoyancy forces are impportant.
A gas
is a supercritical vapor.
Pitot tube measures the __________ of a fluid.
point velocity
Which of the following is not dimension-less?
Kinematic viscosity
In laminar flow through a round tube, the discharge varies
inversely as the viscosity.
Which is not a variable head meter ?
Rotameter
The pipe wall thickness is minimum for a pipe of given nominal size having schedule number
40
Reynolds number for flow of water at room temperature through 2 cm dia pipe at an average velocity of 5 cm/sec is around
1000
Centrifugal pumps as compared to reciprocating pumps
can be run with discharge line valve closed for a short interval.
What type of motion the fluid element undergoes, when it changes from one position to another position, such that the angle between the two sides change ?
Angular deformation
In which type of fluid flow, the velocity of flow of fluid changes from point to point in the fluid at any instant ?
Non-uniform
The continuity equation in ideal fluid flow states that
net rate of inflow into any small volume must be zero.
Bernoulli’s equation is not applicable, when the flow is
all
The equivalent diameter for pressure drop calculation for a duct of square cross-section is given by(where, x = each side of the square duct)
x
Centre of pressure of a plane surface of arbitrary shape immersed vertically in a static mass of fluid
is independent of the specific weight of the fluid.
Drag co-efficient for flow past immersed body is the ratio of __________ to the product of velocity head and density.
average drag per unit projected area
Creeping flow around a sphere is defined, when particle Reynolds number is
< 0.1
Open channel liquid flow is most conveniently measured by a
notch
Toothpaste is a
dilatent
Slurries can be most conveniently pumped by a __________ pump.
centrifugal
Volute type of casing is provided in a centrifugal pump to
increase the discharge.
Each term of the Bernoulli’s equation written in the form, (1) , represents the total energy per unit
mass
In a free vortex, the
velocity changes linearly with radial distance.
Pick out the wrong statement.
a. The eddy viscosity is a function of the type of turbulence involved.
b. The eddy viscosity is a fluid property.
c. The viscosity of gas increases with increase in temperature.
d. The viscosity of a liquid increases with decrease in temperature.
The eddy viscosity is a fluid property.
The velocity distribution in direction normal to the direction of flow in plane Poiseuille flow is
parabolic
In fluid flow, the stagnation point is defined as a point, where the __________ is zero.
flow velocity
A special type of liquid transporting device is the diffuser pump, in which __________ are minimised.
shock losses
Which of the following is most prone to pulsating discharge flow ?
Gear pump
A streamline is
drawn normal to the velocity vector at every point.
Which of the following relationship is valid for the equilibrium position of the float in a rotameter ?(where, Df= Drag force on the float Bf = Buoyant force on the float Wf = Weight of the float)
Df + Bf = Wf
Drag is defined as the force exerted by the
fluid on the solid in the direction of flow.
The boundary layer is that part of a moving fluid, in which the fluid velocity is
affected by the presence of a solid boundary.
The terminal velocity of a solid spherical particle falling through a stationary fluid mass in the Stoke’s law range is proportional to the
all
Which of the following equations as suggested by Colebrook and White gives the increase in roughness of a new surface (ε0) with age/time (t) (where, ε = roughness of the surface after time’t’. α = a co-efficient to be experimentally determined)?
ε = ε0 + α.t
Nominal size of a pipe is an indication of its __________ diameter.
inner
Fluidised beds are formed, when the
fluid friction is zero
A fluid is pumped at the rate of 10 lb/sec to a height of 55 ft. The horse power required is __________ hp.
1
Pick out the wrong statement:
a. The vacuum pressure is always the negative gauge pressure.
b. The pressure of the liquid measured by a piezometer tube is the
gauge pressure.
c. Manometric liquid should have high surface tension.
d. The point at which the resultant pressure on an immersed surface
acts, is known as the centre of gravity.
The point at which the resultant pressure on an immersed surface acts, is known as the centre of gravity.
Medium viscosity lubricating oil can be most ideally pumped by a __________ pump.
vane
In a fully turbulent flow (Re > 105) in a pipe of diameter ‘d’, for a constant pressure gradient, the dependence of volumetric flow rate of an incompressible fluid is
d^2.5
Pump used for the transportation of molten sodium in a fast breader reactor is a/an __________ pump.
electromagnetic
Small pressure differences in liquids is measured using a/an
inclined tube manometer.
With increase in pump speed, its NPSH requirement
increases
In the Newton’s law range, the terminal velocity of a solid spherical particle falling through a stationary fluid mass is __________ the fluid viscosity.
inversely proportional to
Gear pump
is a positive displacement pump.
Most of the centrifugal pumps used in chemical plants are usually __________ driven.
electric motor
Check valve provided in the discharge line of a centrifugal pump serves the purpose of controlling the
back flow of fluid in the event of stoppage of pump.
Venturimeters, orificemeters and nozzles are used to measure the fluid discharge from a pipeline. The average fluid velocity in a pipeline can be measured by a/an
hot wire anemometer
The time taken for gravity flow of a fixed volume of liquid (as in Redwood viscometer) is directly proportional to its
ratio of absolute viscosity to density.
Sewage sludge is __________ type of non-Newtonion fluid.
Bingham plastic
Ratio of pressure and inertia force gives __________ number.
Euler
Permanent loss in a venturimeter is about __________ percent of the pressure drop in theupstream cone.
10 .
Volume of liquid displaced by a floating body is equivalent to its
own weight
The __________ is measured by a piezometric opening.
total pressure
What is the pipe called which lifts water from a reservoir to a greater height than the initial level in the supply reservoir ?
Siphon
Steady uniform flow is represented by flow through a/an
long pipe at constant rate.
Pick out the correct statement pertaining to the flow through a converging-diverging tube.
No shock wave develops in the tube when the Mach number at exit is greater than unity.
Cavitation can be prevented by
maintaining the suction head sufficiently greater than the vapour pressure.
Assuming flow to be laminar, if the diameter of the pipe is halved, then the pressure drop will
increase
Steady flow occurs, when the
conditions do not change with time at any point.
With increase in the ratio of orifice diameter to pipe diameter, the fraction of the orifice pressure differential that is permanently lost
decreases
Which of the following two quantities when same, makes one pipe system equivalent to another pipe system ?
Head & discharge
The kinetic energy correction factor for velocity distribution of laminar flow is
1.66
Priming of a centrifugal pump is done to
avoid chances of separation inside the impeller.
Bed pressure drop in an air fluidised bed of catalyst particles (ρp = 200 kg/m3, Dp = 0.05 cm) of 60 cm bed depth and bed porosity of 0.5 expressed in cm of water (manometer) is
60
For pipes that must be broken at intervals for maintenance, the connector used should be a/an
union
A fluid is the one, which
cannot remain at rest under the action of shear force.
A fluid (1) is moving at critical flow condition (NRe = 2100) through a pipe of dia 3 cms. Velocity of flow is __________ cm/sec.
7
Capillary rise of mercury in a small diameter tube is proportional to (where, d = diameter of the tube, σ = surface tension of mercury)
σ
The pressure drop per unit length of pipe incurred by a fluid ‘X’ flowing through pipe is Δp. If another fluid ‘Y’ having both the specific gravity & density just double of that of fluid ‘X’, flows through the same pipe at the same flow rate/average velocity, then the pressure drop in this case will be
2Δp
Fluid flow in a/an __________ is an example of pressure flow.
pipe
In the laminar boundary layer flow over a flat plate, the ratio (δ/x) varies as :(where, ‘δ’ is the boundary layer thickness and ‘x’ is the distance from the leading edge in the direction of flow).
Re^-1/2
A rotameter through which air at room temperature and atmospheric pressure is flowing gives a certain reading for a flow rate of 100 cc/sec. If helium (molecular weight 4) is used and rotameter shows the same reading, the flow rate (cc/sec) is
269
A 0.5 m high bed made up of a 1 mm dia glass sphere (density 2500 kg/m^3 ) is to be fluidised by water (density 1000 kg/m^3 ). If at the point of incipient fluidisation, the bed voidage is 40%, the pressure drop across the bed is
4.4 KPa
Select the wrong statement pertaining to flow of an incompressible fluid through a venturimeter.
Venturimeter occupies less space than an orificemeter.
Reynolds number for water flow through a tube of I.D. 5 cm is 1500. If a liquid of 5 centipoise viscosity and 0.8 specific gravity flows in the same pipe at the same velocity, then the pressure drop will
increase
The bulk modulus of elasticity of a liquid
increases with pressure.
Curve III in the above diagram represents a/an
pseudo plastic fluid
What is the ratio of total kinetic energy of fluid passing per second to the value obtained on the basis of average velocity (for laminar flow through a circular pipe)?
2
The line traced by a single fluid particle as it moves over a period of time is called __________ line.
path
A stream tube is that, which has __________ cross-section entirely bounded by stream lines.
any convenient
Colebrook equation for friction factor in turbulent flow is given by, (1) . It reduces to Nikuradse equation for a value of (1) equal to
1
The unit of velocity head is
ft-lbf/lb
Which of the following properties of a fluid is responsible for offering resistance to shear ?
Viscosity.
Erosion and pits formation on the impeller of a centrifugal pump may be due to
cavitation.
The velocity profile exhibited by laminar flow of Newtonion fluids is such that the velocity distribution w.r.t. radius of the circular pipe is a/an __________ with the apex at the centre line of the pipe.
parabola
The excess of the sum of pressure & velocity heads over the vapor pressure of the liquid at the suction is called the
net positive suction head (NPSH).
Piezometric head is the sum of the __________ heads.
elevation & pressure
Propellers are
axial flow mixers.
Which of the following is not an advantage of fluidisation from transfer operation point of view?
Lower fluid pumping power requirement.
Upto what value of ‘Mach number’, a fluid may be considered as incompressible ?
0.3
The head developed by a centrifugal pump is largely determined by the
angle of the vanes and the speed of the tip of the impeller.
Pick out the wrong statement:
a. Greater is the kinematic viscosity of the liquid, greater is the
thickness of the boundary layer.
b. Blowers develop a maximum pressure of 2 atmospheres.
c. Friction losses in pipe fittings are generally expressed in terms of
velocity heads.
d. Fanning friction factor in case of turbulent flow of liquids in pipe
depends upon relative roughness & Reynolds number.
Friction losses in pipe fittings are generally expressed in terms of velocity heads.
Flow rate of high velocity flue gas discharged through a stack to the atmosphere can be most conveniently measured by a
pitot tube
Potential flow is the flow of
incompressible fluids with no shear.
The value of critical Reynolds number for pipe flow is
1300
Mach number is important in a fluid flow problem, when the inertia and __________ forces predominate.
elastic
Fanning friction factor is equal to(where, fB = Blassius friction factor).
fB/4
In case of coutte flow, the fluid flow is between two large flat parallel plates with
top plate moving and the bottom plate fixed.
In a stabilised soap bubble, pressure inside it compared to external pressure is
more
The component of acceleration resulting due to unsteady nature of flow is called __________ acceleration.
local
Power required for mixing Newtonion fluids is a function of the
none of these.
Multistage compressors are used in industry, because they
resemble closely to isothermal compression.
The hydrodynamic and thermal boundary layers will merge, when
Prandtl number is one.
Differential manometer measures the
pressure difference between two points.
For a stable equilibrium of a submerged body (where, G and B are centres of gravity & buoyancy respectively).
B is above G
With increase in the ratio of orifice diameter to pipe diameter in case of an orificemeter, the overall pressure loss
remains constant
The vent valve provided in a liquid handling centrifugal pump is
all
The discharge through a semi-circular weir varies as (where, H = Head of liquid.)
H^2
The Mach number for hypersonic flow of compressible fluid is
> 4
Boundary layer thickness in turbulent flow over a flat plate increases as(where, d = distance from the leading edge.)
d^4/5
The valve used for very remote and accurate control of fluid is a __________ valve.
needle
f = 16/NRe, is valid for
none of these
A mixed flow centrifugal pump
employs such an impeller, through which the flow is a combination of radial & axial flow.
In centrifugal pump operation, the cavitation can be eliminated by maintaining suction pressure __________ the vapor pressure of the liquid at the suction temperature.
higher than
A rectangular surface 3’ x 4’, has the lower 3 edge horizontal and 6’ below a free oil surface (sp. gr. 0.8). The surface inclination is 300 with the horizontal. The force on one side of the surface is(where, y = specific weight of water)
48y
A bed of spherical particles (specific gravity 2.5) of uniform size 1500 μm 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 : Δ 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, the minimum fluidisation velocity, VOM is
16 mm/s
One dimensional flow implies
a flow which does not account for changes in transverse direction.
In case of turbulent flow of a Newtonion fluid in a straight pipe, the maximum velocity is equal to (where, Vavg = average fluid velocity)
1.2 Vavg
Centrifugal compressors compared to reciprocating compressors
all
For laminar flow of Newtonion fluids through a circular pipe, for a given pressure drop and length & diameter of pipe, the velocity of fluid is proportional to(where, μ = fluid viscosity )
1/μ
Umf is the minimum fluidisation velocity for a bed of particles. An increase in the superficial gas velocity from 2 Umf to 2.5 Umf results in (all velocities are smaller than the entrainment velocity of the particles) no change in the
bed height
Stoke’s law is valid, when the particle Reynolds number is
< 1
Which of the following is not a dimension-less parameter ?
Kinematic viscosity
In which of the following cases, it is possible for flow to occur from low pressure to high pressure ?
Flow through a converging section.
The blades of a centrifugal impeller are said to be curved forward, if the __________ of the motion of impeller blades.
outlet tip of a blade is towards the direction
For the same terminal conditions and fitting size, the least friction loss is incurred in a/an
union
A floating/submerged body is always stable, if its centre of gravity
lies below its centre of buoyancy.
Critical velocity in a pipe flow
increases as pipe diameter increases.
A centrifugal pump designed to pump water is employed to pump a more viscous oil. In the later case, the pump
All
In an incompressible flow of fluid, the fluid
density does not change with pressure & temperature.
The ratio of maximum to average velocity in case of streamline flow between parallel plates is
1.5
A weir is used to measure the large water discharge rate from a river or from an open channel. A weir is not of __________ shape.
circular
Pressure co-efficient is the ratio of pressure forces to __________ forces.
inertial
Which of the following conditions must be satisfied for lift force to be developed ?
Circulation around the body is essentially required.
The Reynolds number for an ideal fluid flow is
∞
