NCEES Fluid Mechanics 5

Question 1

A submerged gate 1 m wide and 2 m tall has its top edge at 3 m depth. What is the total hydrostatic force on the gate? (ρ = 1000 kg/m³)

Accepted Answer

78,480 N

Answer

F = ρg·ȳ·A where ȳ = 3 + 1 = 4 m (centroid depth); F = 1000×9.81×4×(1×2) = 78,480 N.

Question 2

What does the water hammer phenomenon refer to in pipe systems?

Accepted Answer

Pressure surge caused by rapid valve closure

Answer

Water hammer is a pressure surge or wave caused when a fluid in motion is forced to stop or change direction suddenly, typically by rapid valve closure.

Question 3

For a Venturi meter, which principle is used to determine flow rate?

Accepted Answer

Continuity and Bernoulli equations combined

Answer

A Venturi meter uses the continuity equation (A₁V₁ = A₂V₂) combined with Bernoulli's equation to relate pressure difference to flow velocity.

Question 4

The net positive suction head (NPSH) is important in pump design primarily to avoid:

Accepted Answer

Cavitation

Answer

If the available NPSH falls below the required NPSH, the local pressure drops below vapor pressure and cavitation occurs, damaging the pump.

Question 5

For laminar flow in a circular pipe (Hagen-Poiseuille flow), the velocity profile is:

Accepted Answer

Parabolic

Answer

Hagen-Poiseuille flow produces a parabolic velocity profile: u(r) = (ΔP/4μL)(R² - r²), with maximum velocity at the centerline.

NCEES Practice Test

NCEES Practice Test

NCEES Fluid Mechanics 5