Fluid Mechanics Flashcards
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
Co-efficient of velocity is __________ the coefficient of discharge.
more than
Which of the following is not concerned with the fluid-particle interaction?
A. Drag co-efficient
B. Froude Number
C. Galileo Number
D. Weber Number
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
Brownian movement is prominent in the particle size range of __________ microns in case of settling of a particle in a fluid.
2 to 3
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 10-3m. The top plate is moving with a velocity of 1 m/s. The shear stress on the plate is
20 Kpa
A forced vortex occurs when fluid rotates as a solid about an axis.
Correct
The ratio of maximum to average velocity in case of streamline flow between parallel plates is
1.5
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
With increase in the Mach number >0.6, the drag co-efficient decreases in case of compressible fluids.
Wrong
The ratio of width to depth for the most economical rectangular section in open channel flow is
2
Vena-contracta pressure tapping is at a distance __________ from the position of an orificemeter fitted in a pipe of internal diameter ‘d’
0.5d
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
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 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
Upto what value of ‘Mach number’, a fluid may be considered as incompressible ?
0.3
Friction losses in pipe fittings are generally expressed in terms of velocity heads.
Wrong
Flow rate of high velocity flue gas discharged through a stack to the atmosphere can be most conveniently measured by a
Pitot tube
With increase in the ratio of orifice diameter to pipe diameter in case of an orificemeter, the overall pressure loss
remains constant
The discharge through a semi-circular weir varies as (where, H = Head of liquid.)
H²
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
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 103VOM+ 10.94 x 106V2OM(SI units)
If water is to be used as the fluidising medium, the minimum fluidisation velocity, VOMis
16 mm/s
In case of turbulent flow of a Newtonion fluid in a straight pipe, the maximum velocity is equal to (where,Vavg= average fluid velocity)
1.2Vavg
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
An ideal fluid is the one, which has negligible surface tension and obeys the Newton’s law of viscosity.
Wrong
For pipe flows, head is proportional to __________ at constant capacity(where,D= pipe diameter).
1/D5
What is the ratio of fluid carrying capacity of two pipes having diametersd1andd2respectively ?
(d1/d2)⁰•⁵
In case of a centrifugal pump, the ratio of total delivered pressure to pressure developed with the impeller is called the __________ efficiency.
manometric
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
For ideally incompressible fluid, the Mach number will be
1
In case of isentropic flow, the speed of sound in an ideal gas is proportional to (whereM= molecular weight of the gas)
1/√M
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
A pitched-blade turbine draws __________ a straight blade turbine.
ε = ε0+ α.t
Nominal size of a pipe is an indication of its __________ diameter.
approximate
A fluid is pumped at the rate of 10 lb/sec to a height of 55 ft. The horse power required is __________ hp.
1
The point at which the resultant pressure on an immersed surface acts, is known as the centre of gravity.
Wrooooooong
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
d2.5
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
The exit cone angle in case of a standard venturimeter is __________ the entrance cone angle.
smaller than
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
No shock wave develops in the tube when the Mach number at exit is greater than unity.
Correctueee
Assuming flow to be laminar, if the diameter of the pipe is halved, then the pressure drop will
increase
With increase in the ratio of orifice diameter to pipe diameter, the fraction of the orifice pressure differential that is permanently lost
decreases
The kinetic energy correction factor for velocity distribution of laminar flow is
1.66
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
A fluidis 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
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/m3) is to be fluidised by water (density 1000 kg/m3). If at the point of incipient fluidisation, the bed voidage is 40%, the pressure drop across the bed is
4.4 kPa
Venturimeter occupies less space than an orificemeter.
Wrooonggg
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
