Section 8 Flashcards
One poise (unit of absolute/dynamic viscosity) is equivalent to one
a. gm/cm2. sec.
b. gm/cm. sec.
c. cm2/sec.
d. m2/sec.
b. gm/cm. sec.
The equation relating friction factor to Reynold number, f^-0.5 = 4 loge (NRe/f)^0.4, is called the equation.
a. Nikuradse
b. Von-Karman
c. Blausius
d. Colebrook
a. 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 ?
a. 0.64
b. 1.65
c. 0.32
d. 0.94
a. 0.64
For an unstable equilibrium of a floating body (where, M = metacentre.)
a. M is above G
b. M is below G
c. M & G coincide
d. none of these
b. M is below G
Which of the following can be used for the direct measurement of volumetric flow rate of slurry ?
a. Venturimeter
b. Orificemeter
c. Rotameter
d. Pitot tube
c. Rotameter
A pipe is defined as ‘hydraulically smooth’, if the friction factor
a. is not a function of Reynolds number.
b. for a given Reynolds number remains constant even on further
smoothening of the pipe.
c. is zero irrespective of the Reynolds number.
d. none of these.
b. for a given Reynolds number remains constant even on further
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
a. 5
b. 14.1
c. 56.22
d. 28.2
d. 28.2
Delivery of insufficient quantity of liquid by a pump may be caused by
a. air leak in the inlet
b. low rpm
c. too high a lift
d. all (a), (b) and (c)
d. all (a), (b) and (c)
In case of a __________ the energy of flow is considerably decreased downstream of the machine.
a. blower
b. turbine
c. centrifugal pump
d. centrifugal fan
b. turbine
With increase in the shear rate, the apparent viscosity of pseudoplastic fluids
a. increases
b. decreases
c. remains same
d. may increase or decrease; depends on the magnitude of shear rate
b. 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
a. 0.42
b. 0.62
c. 0.82
d. 0.98
b. 0.62
Purpose of hydraulic accumulator is to
a. ensure intermittant supply of hydraulic pressure.
b. increase the pressure and store/ accumulate it.
c. accumulate pressure to increase force.
d. generate high pressure to operate hydraulic machines like cranes, lifts, presses etc
d. 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.
c. 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
a. protect the pump against developing excessive pressure.
b. facilitate unidirectional flow of liquid.
c. reduce the discharge pressure.
d. control the rate of discharge.
a. protect the pump against developing excessive pressure.
Select the correct statement.
a. The discharge through a venturimeter depends upon Δp only and is independent of orientation of the meter.
b. A venturimeter with a given gage difference discharges at a greater rate, when the flow is vertically downward through it, than when the flow is vertically upward.
c. For a given pressure difference, the discharge of gas is greater through a venturimeter, when compressibility is taken into account, than when it is neglected.
d. The overall pressure loss is the same in a given pipe line, whether a venturimeter or a nozzle with the same throat dia is used.
a. 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
a. mean flow velocity is about 0.5 times the maximum velocity.
b. velocity profile becomes flatter and flatter with increasing Reynolds number.
c. point of maximum instability exists at a distance of 2r/3 from the pipe wall (r = pipe radius).
d. skin friction drag, shear stresses, random orientation of fluid particles and slope of velocity profile at the wall are more.
d. skin friction drag, shear stresses, random orientation of fluid particles and slope of velocity profile at the wall are more.
For the same terminal conditions and valve size, the pressure drop in a fully opened globe valve as compared to that in a gate valve is
a. more
b. less
c. equal
d. either (a) or (b); depends on the viscosity of the fluid
a. more
What is the maximum theoretical suction lift (metres) of a reciprocating pump ?
a. 5
b. 10
c. 50
d. 100
b. 10
The terminal velocity of a particle moving through a fluid varies as dpn. The value of n is equal to in Stoke’s law regime.
a. 1
b. 0.5
c. 2
d. 1.5
c. 2
Function of air vessel provided in a reciprocating pump is to
a. reduce discharge fluctuation.
b. reduce the danger of cavitation.
c. avoid the necessity of priming.
d. increase the pump efficiency.
a. reduce discharge fluctuation.
The Prandtl pitot tube measures the
a. velocity at a point in the flow.
b. pressure at a point.
c. average flow velocity.
d. pressure difference in pipe flow.
a. velocity at a point in the flow.
Pressure drop in packed bed for turbulent flow is given by the equation.
a. Kozney-Karman
b. Blake-Plummer
c. Leva’s
d. Hagen-Poiseulle’s
b. Blake-Plummer
In the complete turbulence zone (in rough pipes), the
a. rough and smooth pipes have the same friction factor.
b. laminar film covers the roughness projections.
c. friction factor depends upon NRe only.
d. friction factor is independent of the relative roughness.
d. friction factor is independent of the relative roughness.
Which of the following has the minimum compressibility ?
a. Water at room temperature
b. Air at room temperature
c. Oxygen at room temperature
d. Nitrogen at room temperature
a. Water at room temperature
In case of centrifugal fan or blower, the gas capacity varies as
a. speed
b. (speed)^2
c. (speed)^3
d. (speed)^0.5
a. speed
Pick out the wrong statement.
a. A fluid mass is free from shearing forces, when it is made to rotate with a uniform velocity.
b. Newton’s law of viscosity is not applicable to the turbulent flow of fluid with linear velocity distribution.
c. Laminar flow of viscous liquids is involved in the lubrication of various types of bearings.
d. Rise of water in capillary tubes reduces with the increasing diameter of capillary tubes.
b. 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.
a. 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
a. parabolic
b. flat
c. flat near the wall and parabolic in the middle
d. parabolic near the wall and flat in the middle.
d. parabolic near the wall and flat in the middle.
Mach number is the ratio of the speed of the
a. fluid to that of the light.
b. light to that of the fluid.
c. fluid to that of the sound.
d. sound to that of the fluid.
c. fluid to that of the sound.
A piezometer opening measures the __________ fluid pressure.
a. static
b. undisturbed
c. total
d. dynamic
b. undisturbed
Drag force on the float of a rotameter is(where Q = flow rate of the )
a. ∝Q
b. ∝Q
c. ∝Q2
d. Constant
d. Constant
The unit of dynamic viscosity in SI unit is
a. kg/m . sec
b. N/m2
c. m2 /sec.
d. m/N. sec.
a. kg/m . sec
Pressure drop (Δp) for a fluid flowing in turbulent flow through a pipe is a function of velocity (V) as
a. V^1.8
b. V^-0.2
c. V^2.7
d. V^2
d. V^2
Dean number is concerned with the
a. fluid-particle interaction.
b. fluid flow through helical pipes.
c. power consumption in agitated vessels.
d. psychrometry.
b. fluid flow through helical pipes.
The equation given below is called the __________
f-0.5 = 4.07 loge (NRef)-0.6
a. Colebrook formula
b. Von-Karman equation
c. Fanning equation
d. none of these
b. Von-Karman equation
Poise is converted into stoke by
a. multiplying with density (gm/c.c).
b. dividing by density (gm/c.c).
c. multiplying with specific gravity.
d. dividing by specific gravity.
b. 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.
a. dilatant
b. pseudoplastic
c. Bingham plastic
d. Newtonion
a. dilatant
Kinetic energy of fluid per unit weight represented by the velocity head is given by
a. 2v^2 /gc
b. v^2 /2gc
c. ρv^2 /gc
d. ρ.v^2 /2gc
b. v^2 /2gc
At a constant speed of the centrifugal pump . it __________ the impeller diameter.
a. capacity varies directly with
b. head varies as the square of
c. horsepower varies as the cube of
d. all (a), (b) and (c)
d. all (a), (b) and (c)
The pressure co-efficient is the ratio of pressure forces to __________ forces.
a. viscous
b. inertial
c. gravity
d. surface tension
a. viscous
Vena-contracta formed during flow of a liquid through an orificemeter has
a. minimum liquid cross-section.
b. more diameter compared to orifice diameter.
c. minimum velocity of fluid stream.
d. none of these.
a. 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)
a. 1/μ
b. μ
c. μ2
d. 1/μ2
b. μ
Horsepower increase of a centrifugal gas compressor without altering the volumetric flow rate will __________ the gas discharge pressure.
a. increase
b. decrease
c. not change
d. exponentially decrease
a. increase
In continuous fluidisation
a. solids are completely entrained.
b. the pressure drop is less than that for batch fluidisation.
c. there is no entrainment of solids.
d. velocity of the fluid is very small.
a. solids are completely entrained.
