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 normal stress is the same in all directions at a point in a fluid, when the fluid is
having no motion of one fluid layer relative to the other.
Head developed by a centrifugal pump depends on its
both (a) and (b)
Hydraulic mean depth (Dm) for a circular pipe of diameter ‘D’ flowing full is 0.25 D. For a circular channel, at Dm = 0.3 D, gives the condition for the maximum
mean velocity
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
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
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 (a), (b) and (c)
The fluid in which the shearing stress within it is proportional to the velocity gradient across the sheared section, is called a __________ fluid.
Newtonion
In fluid flow, cavitation is caused, if the
flow pressure approaches its vapor pressure at the prevailing temperature.
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 10-6m2/s).
0.44
The maximum delivery pressure of compressors can be up to __________ atmospheres.
1000
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
Pick out the wrong statement.
both (b) and (c)
Pressure drag does not depend upon the
all (a), (b) and (c)
__________ 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
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 center 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 line of action of the buoyant force passes through the centre of gravity of the
displaced volume of the fluid.
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 fluidized 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.
With diminishing cross-sectional area in case of subsonic flow in a converging nozzle, the
both (a) & (b)
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
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 falling rain drops to acquire spherical shape is its
surface tension
The simple pitot tube does not measure the
all a, b ,c
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.
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
A centrifugal pump loses prime after starting. The reason of this trouble may be
all (a), (b), and (c)
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 column 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.
The Navier-Stokes equation deals with the law of conservation of
momentum
Hydraulic intensifier is used for increasing the
intensity of pressure of the liquid.
Hydrometer measures the specific gravity of liquids based on the principles of buoyancy. Pycnometer is used to measure the specific gravity of
all ‘a’, ‘b’ & ‘c’
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 a given Reynold number as d/D for an orifice increases, Cd will (where, d & D are orifice & pipe diameters respectively).
increase
A differential pressure cell is used for
remote recording of pressure difference.
In case of a centrifugal pump, the ratio of total delivered pressure to pressure developed with the impeller is called the __________ efficiency.
manometric
If more than two branches of pipes are to be connected at the same point, then use a/an
tee
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.
Check in a centrifugal pump is
all (a), (b) and (c).
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
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
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
An ideal nozzle design aims at
both (a) & (b)
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
Theoretical head developed by a centrifugal pump does not depend upon the __________ the impeller.
none of these
Higher specific speed (200-500) of a centrifugal pump indicates that the pump is of __________ flow type
axial
A mono pump is a __________ pump
positive acting rotary
An ideal fluid is
both (a) & (b)
Boundary layer separation is caused by the
adverse pressure gradient.
With increase in temperature, the vapor pressure of liquids
increases
The ratio of wall drag to total drag in the Stoke’s law range is
2/3
