BCE Hydraulics & Fluid Mechanics 1 — Questions and Answers
Question 1: What does Bernoulli's equation primarily conserve in fluid flow?
- Mass
- Energy (Correct answer)
- Momentum
- Pressure
Correct answer: Energy
Bernoulli's equation is a statement of the conservation of energy along a streamline in steady, incompressible, frictionless flow.
Question 2: Which dimensionless number represents the ratio of inertial forces to viscous forces in fluid flow?
- Froude number
- Weber number
- Reynolds number (Correct answer)
- Mach number
Correct answer: Reynolds number
The Reynolds number (Re = ρVD/μ) represents the ratio of inertial to viscous forces and determines whether flow is laminar or turbulent.
Question 3: What is the hydraulic radius of a circular pipe flowing full with diameter D?
- D/2
- D/4 (Correct answer)
- D
- πD/4
Correct answer: D/4
For a full circular pipe, hydraulic radius R = Area/Wetted Perimeter = (πD²/4)/(πD) = D/4.
Question 4: Manning's equation is primarily used to calculate flow in which type of system?
- Pressurized pipe flow
- Open channel flow (Correct answer)
- Pump systems
- Compressible gas flow
Correct answer: Open channel flow
Manning's equation (V = (1/n)R^(2/3)S^(1/2)) is used to compute velocity and discharge in open channel flow.
Question 5: Which type of flow occurs when the Froude number is less than 1 in an open channel?
- Supercritical flow
- Critical flow
- Subcritical flow (Correct answer)
- Turbulent flow
Correct answer: Subcritical flow
When Fr < 1, the flow is subcritical (tranquil), meaning gravitational forces dominate over inertial forces.
Question 6: The specific energy in an open channel is defined as the energy head measured above which datum?
- Sea level
- The channel bottom (Correct answer)
- The water surface
- The centerline of flow
Correct answer: The channel bottom
Specific energy E = y + V²/2g is the total energy per unit weight measured with respect to the channel bottom as datum.
BCE Hydraulics & Fluid Mechanics 1
What does Bernoulli's equation primarily conserve in fluid flow?