NCEES Fluid Mechanics 4

Question 1

A fluid with viscosity μ = 0.001 Pa·s flows between parallel plates 1 mm apart; the top plate moves at 1 m/s. What is the shear stress on the plates?

Accepted Answer

1 Pa

Answer

τ = μ(du/dy) = 0.001 × (1/0.001) = 0.001 × 1000 = 1 Pa.

Question 2

The specific gravity of a fluid is defined as the ratio of its density to the density of:

Accepted Answer

Water at 4°C

Answer

Specific gravity is the dimensionless ratio of a fluid's density to pure water's density at 4°C (1000 kg/m³).

Question 3

For flow over a flat plate, the boundary layer thickness δ grows proportionally to:

Accepted Answer

x^(1/2)

Answer

For laminar flow over a flat plate, the Blasius solution gives δ ∝ x^(1/2) (or δ/x = 5/√Re_x).

Question 4

Which valve type is best suited for throttling (flow control) applications?

Accepted Answer

Globe valve

Answer

Globe valves are specifically designed for throttling because their disc movement is perpendicular to flow, providing precise control.

Question 5

A 6-inch schedule 40 steel pipe has a length of 100 ft and a friction factor f = 0.02. What is the Darcy-Weisbach head loss if water flows at 5 ft/s? (D = 0.5054 ft)

Accepted Answer

1.54 ft

Answer

hf = f(L/D)(V²/2g) = 0.02×(100/0.5054)×(25/64.4) = 0.02×197.9×0.388 ≈ 1.54 ft.

NCEES Practice Test

NCEES Practice Test

NCEES Fluid Mechanics 4