ME or MEng Master of Engineering Fluid Mechanics and Hydraulics 2 — Questions and Answers
Question 1: The Moody diagram relates friction factor to Reynolds number and:
- Fluid density
- Relative roughness (ε/D) (Correct answer)
- Flow temperature
- Pipe length
Correct answer: Relative roughness (ε/D)
The Moody diagram plots Darcy friction factor against Reynolds number and relative roughness ε/D for pipe flow.
Question 2: Archimedes' principle states that the buoyant force on a submerged object equals:
- The weight of the object
- The weight of fluid displaced by the object (Correct answer)
- The pressure at the object's centroid times its volume
- The surface tension force times the perimeter
Correct answer: The weight of fluid displaced by the object
The buoyant force equals the weight of the fluid displaced, acting upward through the center of buoyancy.
Question 3: A Venturi meter measures flow rate by exploiting which principle?
- Pressure increases as velocity increases
- Pressure decreases as velocity increases (Correct answer)
- Velocity is constant across a constriction
- Fluid density changes with velocity
Correct answer: Pressure decreases as velocity increases
A Venturi meter measures the pressure drop across a converging section; lower pressure at the throat (where velocity is higher) via Bernoulli's equation allows flow rate calculation.
Question 4: In open-channel flow, the Froude number less than 1 indicates:
- Supercritical flow
- Subcritical (tranquil) flow (Correct answer)
- Laminar flow
- Turbulent flow
Correct answer: Subcritical (tranquil) flow
Fr = V/√(gy) < 1 indicates subcritical or tranquil flow, where gravity waves can propagate upstream.
Question 5: Hydraulic diameter D_h for a non-circular duct is defined as:
- 4 × Cross-sectional area / Wetted perimeter (Correct answer)
- Cross-sectional area / Wetted perimeter
- Perimeter / Cross-sectional area
- Square root of the cross-sectional area
Correct answer: 4 × Cross-sectional area / Wetted perimeter
D_h = 4A/P allows pipe-flow correlations to be applied to non-circular ducts by using an equivalent hydraulic diameter.
Question 6: The Navier-Stokes equations describe:
- Heat transfer in solids
- Motion of viscous fluid substances (Correct answer)
- Electrical current in conductors
- Deformation of elastic solids under load
Correct answer: Motion of viscous fluid substances
The Navier-Stokes equations are nonlinear partial differential equations describing the motion of viscous, Newtonian fluids.
ME or MEng Master of Engineering Fluid Mechanics and Hydraulics 2
The Moody diagram relates friction factor to Reynolds number and: