Momentum Transfer (Set 1) Flashcards
As one of the transport phenomena, the concepts in momentum transfer (also known as fluid mechanics) are crucial for the design, operation, and maintenance of fluid flow equipment such as pipes, pumps/compressors, turbines/expanders, agitators, and metering devices.
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.
a. static
b. total
c. difference in static & dynamic
all of these
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
a. roughness of surface of the body.
b. pressure of main flow only.
c. length of the body in flow direction.
all of these
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 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.
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)
0.043078704
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 >> 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
a. smoothens the flow by avoiding pulsations.
b. increases the volumetric efficiency of the pump.
c. saves the pump from the danger of cavitation.
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
a. static pressure.
b. dynamic pressure.
c. velocity at the stagnation point.
all of these
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
a. incomplete priming.
b. too high a suction lift.
c. low available NPSH and air leaks in the suction pipe.
all of these
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
a. powder & grannular solids
b. liquids
c. low melting point semi-solids
all of these
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.
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
a. provided in the discharge line.
b. generally a globe valve.
c. provided to prevent liquid from backing up through the pump when the pump is turned off or accidently stops running.
all of these
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.
a. radius of
b. speed of
c. fluid velocity leaving
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.
a. accelerating frictionless
b. static
c. uniformly moving
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.
a. The length of entrance region of pipe, in which full development of fluid flow takes place such that velocity profile does not change downstream, is called the transition length.
b. Transition length for laminar flow of Newtonion fluids in a pipe of diameter ‘d’ is equal to 0.05. D.NRe.
c. Transition length for turbulent flow of Newtonion fluids in a smooth pipe of diameter ‘d’ is equal to 50 D.
all of these
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 of these
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 of these
pipe length, fluid velocity in the pipe, time taken to close the valve
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 of these
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 of these.
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
