Fluid Mechanics Flashcards
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.
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
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.
The velocity profile for turbulent flow through a closed conduit is
logarithmic
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
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 pitot static tube does not measure the __________ pressure.
all (a), (b) and (c)
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 upto __________ atmospheres.
1000
Dimension of surface tension is(where, F = force, L = length)
FL^-1
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
__________ 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.
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
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 For ideally incompressible fluid, the Mach number will be
>0.6, the drag co-efficient decreases in case of compressible fluids.
What causes convective acceleration in fluid flow ?
Non-uniformity of flow
The Stoke’s stream function applies to the
cases of axial symmetry.
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
velocity increases and
pressure decreases
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
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.
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 simple pitot tube does not measure the
static pressure.
dynamic pressure.
velocity at the stagnation point.
Boundary layer separation occurs when the
cross-section of the channel is reduced.
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
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.
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.
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
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.
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
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 )
sqrt 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
Check valves are used
for unidirectional flow.
Velocity distribution for flow between two fixed parallel plates
varies parabolically across the section.