Free Fluid Flow Operations MCQs with Answers

• A. Both A. & B.
• B. Rheopectic
• C. Thixotropic
• D. Neither A. nor B.

Explanation: Thixotropic and rheopectic fluids show time-dependent rheological behaviour: their stress-rate relationship changes with the duration of…

• A. Always below the centroid of the area
• B. Always above the centroid of the area
• C. A point on the line of action of the resultant force
• D. At the centroid of the submerged area

Explanation: The centre of pressure is the point through which the resultant hydrostatic force acts, so it lies on the resultant force's line of…

• A. None of these
• B. Decreases linearly with V
• C. Decreases as V2
• D. Increases linearly with V

Explanation: For a sphere at very low Reynolds number, Stokes' law gives drag force F_D = 3πμdV, so drag increases linearly with velocity.

• A. Tungsten
• B. Copper
• C. Chromium
• D. Aluminium

Explanation: Tungsten is used for the heated resistance wire because it tolerates high temperature and has a useful temperature-dependent electrical…

• A. Inverse of fluid viscosity
• B. All A., B. and C.
• C. Difference in the densities of the particle & fluid
• D. Square of particle size

Explanation: In the Stokes-law range, terminal velocity is proportional to (ρp − ρf)d²/μ, so it increases with the density difference and the square of…

• A. Weir
• B. Kennison nozzle
• C. Pitot tube
• D. V-notch

Explanation: A Pitot tube is suitable for very large pipelines because it measures local velocity through pressure difference and causes very little…

• A. Is zero for incompressible liquid
• B. Decreases with pressure
• C. Is independent of temperature & pressure
• D. Increases with pressure

Explanation: The bulk modulus measures resistance to volume compression, and liquids generally become harder to compress as pressure rises.

• A. 1/√M
• B. √M
• C. 1/M
• D. M

Explanation: For an ideal gas, the isentropic sound speed is proportional to √(γRT/M). With temperature and γ fixed, this gives a dependence of 1/√M.

• A. Re
• B. √Re
• C. Re-1/2
• D. 1/Re

Explanation: For a laminar flat-plate boundary layer, δ is proportional to √x, so δ/x is proportional to 1/√x or Re_x^-1/2.

• A. Minimising wall friction
• B. Suppressing boundary layer separation
• C. Neither A. nor B.
• D. Both A. & B.

Explanation: A good nozzle design reduces wall-friction losses and maintains an attached boundary layer to prevent separation.

• A. 550 lbf.ft/second
• B. 550 kgf.m/second
• C. Both A. and B.
• D. 550 lbf.ft./hr

Explanation: The mechanical horsepower definition is 1 hp = 550 lbf·ft/s. The metric expression 550 kgf·m/s is not equivalent to one horsepower, making…

• A. √T
• B. 1/T
• C. 1/√T
• D. T

Explanation: The ideal-gas sound-speed relation is a = √(γRT), so with γ and molecular weight fixed, sound speed varies as the square root of absolute…

• A. Increases
• B. Decreases
• C. Remains unchanged
• D. Increases exponentially

Explanation: Increasing the orifice-to-pipe diameter ratio reduces the vena-contracta effect and improves pressure recovery downstream.

• A. Increases the work done during delivery stroke
• B. Decreases the work done during suction stroke
• C. Does not change the work requirement of the pump
• D. Increases the work done during suction stroke

Explanation: Acceleration head raises the required head during part of a stroke and lowers it during another part.

• A. Blower
• B. Centrifugal fan
• C. Centrifugal pump
• D. Turbine

Explanation: A turbine extracts energy from the flowing fluid and converts it into shaft work, so the fluid energy is substantially lower after the…

• 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

Explanation: In a hydraulically smooth pipe, roughness is too small to affect the flow, so the friction factor depends only on Reynolds number.

• A. Fluid-particle interaction
• B. Power consumption in agitated vessels
• C. Fluid flow through helical pipes
• D. Psychrometry

Explanation: The Dean number characterizes the effect of curvature on flow, especially the secondary circulation produced when fluid moves through a…

• A. 10
• B. 100
• C. 250
• D. 1000

Explanation: Multistage compressors can achieve very high discharge pressures, with maximum values commonly quoted up to about 1000 atmospheres.

• A. Speed
• B. (Speed)2
• C. (Speed)3
• D. (Speed)0.5

Explanation: For geometrically similar centrifugal fans at constant gas density, the fan laws give capacity proportional to speed, head proportional to…

• A. L2T-1
• B. ML-1T-1
• C. LT-2
• D. ML-1T-2

Explanation: Dynamic viscosity is shear stress divided by velocity gradient, giving dimensions of pressure multiplied by time: ML⁻¹T⁻¹.