Free Fluid Flow Operations MCQs with Answers

• A. Decreasing the size of the inlet pipe
• B. Increasing the size of the inlet pipe
• C. Lowering the pump position
• D. Both B. and C.

Explanation: Increasing the inlet-pipe size reduces suction-side friction loss, while lowering the pump improves the available suction head and reduces…

• A. Euler
• B. Froude
• C. Reynold
• D. Mach

Explanation: The Euler number compares pressure forces with inertial forces, Eu = ΔP/(ρv²), apart from the convention-dependent factor of two.

• A. 0.1
• B. 0.55
• C. 0.95
• D. 1.85

Explanation: For maximum discharge, maximizing A^(5/3)/P^(2/3) for a circular section gives a flow depth of about 0.94 times the diameter.

• A. Gravitational & buoyant
• B. Centrifugal & drag
• C. Gravitational or centrifugal buoyant drag
• D. External, drag & viscous

Explanation: A settling particle is acted on by its weight, buoyancy, and fluid drag; in centrifugal settling, the gravitational force is replaced or…

• A. Both A. and B.
• B. Cohesion
• C. Rate of transfer of molecular momentum
• D. Neither A. nor B.

Explanation: Shear resistance arises from molecular momentum transfer between fluid layers and from intermolecular cohesion.

• A. Df = Bf + Wf
• B. Df + Bf = Wf
• C. Df + Bf + Wf =0
• D. None of these

Explanation: At the rotameter float's equilibrium position, the upward drag and buoyant forces balance its downward weight, giving Df + Bf = Wf.

• A. Blasius
• B. Von-Karman
• C. Nikuradse
• D. Colebrook

Explanation: The stated smooth-pipe turbulent-flow correlation is commonly identified as the Nikuradse equation.

• A. Incompressible
• B. Non-viscous
• C. Neither A. nor B.
• D. Both A. and B.

Explanation: The basic Bernoulli equation assumes steady incompressible, inviscid flow with no shaft-work exchange; viscosity would introduce…

• A. Irrotational and frictionless flow
• B. Irrotational and frictional flow
• C. One in which dissipation of mechanical energy into heat occurs
• D. Formation of eddies within the stream

Explanation: Potential flow has zero vorticity, so it is irrotational, and the ideal-flow model neglects viscous friction.

• A. 1 x 10^-3 to 2 x 10^-3 kg/m.s
• B. 1 to 2 kg/m.s
• C. 0.5 x 10^-3 to 1 x 10^-3 kg/m.s
• D. 0.5 to 1 kg/m.s

Explanation: Water at 40°C has a dynamic viscosity of about 0.65 × 10^-3 kg/(m·s), which lies within 0.5 × 10^-3 to 1 × 10^-3 kg/(m·s).

• A. Applicable to laminar flow problems
• B. A universal constant
• C. None of these
• D. Zero at the pipe wall

Explanation: Prandtl's mixing length represents the turbulent momentum-transfer distance and must fall to zero at a solid wall because fluid velocity…

• A. Both A. and B.
• B. Proportional to the fluid velocity
• C. Due to the motion of conducting fluid through an externally generated uniform field
• D. Neither A. nor B.

Explanation: A magnetic flowmeter uses Faraday's law: a conducting fluid moving through an externally applied magnetic field generates a voltage…

• A. Rubber latex
• B. Non-colloidal solution
• C. Quicksand
• D. Sewage sludge

Explanation: A non-colloidal solution generally follows Newton's law of viscosity, so its shear stress is proportional to velocity gradient.

• A. Stream line body
• B. Two dimensional body
• C. Bluff body
• D. None of these

Explanation: A bluff body causes flow separation and a large wake, producing substantial pressure or form drag.

• A. Less than atmospheric pressure
• B. More than liquid vapor pressure
• C. More than atmospheric pressure
• D. Less than liquid vapor pressure

Explanation: Cavitation starts when the local absolute pressure falls below the liquid's vapour pressure, allowing vapour bubbles to form.

• A. Discharge of water by a centrifugal pump being run at a constant rpm
• B. Low velocity flow of a highly viscous liquid through a hydraulically smooth pipe
• C. Water discharge from a vertical vessel in which constant level is maintained
• D. Water flow in the suction and discharge pipe of a reciprocating pump

Explanation: A reciprocating pump produces pulsating suction and discharge, so the velocity and flow rate at a fixed position vary with time.

• A. Affected by the fluid flow pressure
• B. Affected by the presence of a solid boundary
• C. Constant
• D. All A., B. and C.

Explanation: The boundary layer is the region next to a solid surface where viscous effects make the fluid velocity differ from the external-flow…

• A. 1
• B. 0
• C. < 1
• D. > 1

Explanation: In turbulent pipe flow, pressure drop varies approximately as a power of velocity greater than one, such as ΔP proportional to velocity…

• A. 0.003
• B. 0.01
• C. 0.1
• D. 0.3

Explanation: For a smooth pipe at Reynolds number 10^6, the Fanning friction factor is about 0.0025 to 0.003, using the Blasius-type correlation as an…

• A. Friction factor is independent of the relative roughness
• B. Laminar film covers the roughness projections
• C. Friction factor depends upon NRe only
• D. Rough and smooth pipes have the same friction factor

Explanation: In the complete turbulence zone, viscous effects are negligible and the friction factor no longer changes appreciably with Reynolds…