Free Fluid Flow Operations MCQs with Answers

• A. 1
• B. 10
• C. 30
• D. 50

Explanation: A well-designed Venturi meter has low irreversible losses because its gradual contraction and expansion minimise separation.

• A. 2100
• B. 100
• C. 0
• D. ∞

Explanation: For an ideal fluid, viscosity is zero, so the Reynolds number, Re = ρvD/μ, tends to infinity.

• A. Due to the weight of the atmospheric air, that it displaces
• B. Increased, as it rises to a higher altitude
• C. Not dependent on the temperature of the atmosphere
• D. None of these

Explanation: A balloon is lifted by buoyancy, which equals the weight of the atmospheric air displaced by it.

• A. Globe valve
• B. Butterfly valve
• C. Needle valve
• D. None of these

Explanation: Butterfly valves are compact, lightweight, and relatively inexpensive for controlling flow in large-diameter pipes.

• A. 4x
• B. 2x
• C. √x
• D. x

Explanation: The equivalent or hydraulic diameter is 4A/P, where A is flow area and P is wetted perimeter.

• A. All A., B. and C.
• B. Fluid viscosity
• C. Density of both the particle & the fluid
• D. Particle size

Explanation: The minimum fluidisation velocity is determined by the balance between particle weight and fluid drag, so it depends on particle size…

• A. Dependent on its cross-sectional area
• B. The velocity of sound
• C. Dependent on fluid viscosity
• D. Dependent on fluid density

Explanation: For a constant-area passage, the limiting maximum velocity in compressible flow is the sonic velocity, corresponding to Mach number one.

• A. 4f (L/D) (v2/2gc) ρ
• B. 32 (μLV/gc D2)
• C. 16/NRe
• D. (fLρ/D) (v2/2gc)

Explanation: For fully developed laminar flow in a circular pipe, the Hagen–Poiseuille relation gives ΔP = 32μLV/(gcD²), matching option b.

• A. 4(Ro-Ri)
• B. √(Ro-Ri)
• C. 2(Ro-Ri)
• D. Ro + Ri

Explanation: For an annulus, Dh = 4A/P = 4π(Ro² − Ri²)/[2π(Ro + Ri)]. Factoring the difference of squares reduces this to 2(Ro − Ri).

• A. VX = V0 + q (x3/L2D)
• B. VX = V0 + ⅓q (x3/L2)
• C. VX = V0 + 2q (x2/LD)
• D. VX = V0 + (4/3) q (x3/L2D)

Explanation: Continuity gives dV/dx = [q(x/L)²]P/A, and for a circular pipe P/A = 4/D.

• A. Viscous
• B. Non-viscous
• C. Turbulent
• D. Rotational

Explanation: The Navier-Stokes equation includes viscous shear-stress terms, so it is the governing equation for viscous fluid motion.

• A. Directly as the velocity
• B. Inversely as the square of the velocity
• C. Approximately as the square of the velocity
• D. Inversely as the square of the diameter

Explanation: From the Darcy-Weisbach relation, head loss is proportional to f(v²/2g), and the friction factor changes only moderately with velocity in…

• A. H
• B. 14.6 H
• C. 13.6 H
• D. 12.6 H

Explanation: For a mercury-water differential manometer, the pressure head in water is (13.6 − 1)H = 12.6H mm of water.

• A. Compressors
• B. Blowers
• C. Fans
• D. Vacuum pumps

Explanation: Fans and blowers produce relatively small pressure rises, whereas compressors are designed to produce the large pressure differences…

• A. Centrifugal
• B. Diffusion
• C. Jet ejector
• D. Piston

Explanation: A diffusion pump uses vapour jets to entrain gas molecules and can produce very high vacuum after a backing pump has lowered the initial…

• A. Highly viscous liquid
• B. Low head but high discharge
• C. High head
• D. Slurries of high solid concentration

Explanation: A multistage centrifugal pump adds the head developed by several impellers in series, making it suitable for high-head service.

• A. Static pressure
• B. Dynamic pressure
• C. Velocity at the stagnation point
• D. All A., B. and C.

Explanation: A simple Pitot tube senses stagnation pressure, while static and dynamic pressures require separate pressure measurement or comparison.

• A. A, B, E
• B. B, D, E
• C. A, C, D
• D. A, D, E

Explanation: The usual Bernoulli derivation assumes steady, frictionless or inviscid, incompressible flow, with irrotational flow allowing the equation…

• A. Surface roughness and curvature (i.e. sharp corners)
• B. Vibration
• C. All A., B. & C.
• D. Pressure gradient and the compressibility of the flowing medium

Explanation: Disturbances such as roughness, sharp curvature, vibration, and adverse pressure gradients can amplify flow disturbances and promote…

• A. Viscous forces are unimportant
• B. Viscous forces control
• C. Gravity forces control
• D. Viscous forces control and inertial forces are unimportant

Explanation: A low Reynolds number means inertial forces are small compared with viscous forces, so viscosity controls the flow behaviour.