NCEES Fluid Mechanics 2

Question 1

A pipe suddenly expands from a diameter of 0.1 m to 0.2 m. If the velocity in the smaller pipe is 4 m/s, what is the head loss due to the sudden expansion?

Accepted Answer

0.046 m

Answer

Using the Borda-Carnot equation: hL = (V1 - V2)²/2g; V2 = 4×(0.1/0.2)² = 1 m/s; hL = (4-1)²/(2×9.81) ≈ 0.459 m.

Question 2

Which dimensionless number represents the ratio of inertial forces to viscous forces in fluid flow?

Accepted Answer

Reynolds number

Answer

The Reynolds number (Re = ρVL/μ) is the ratio of inertial to viscous forces and governs laminar vs. turbulent flow.

Question 3

For a Newtonian fluid, the shear stress is proportional to:

Accepted Answer

The velocity gradient

Answer

For a Newtonian fluid, τ = μ(du/dy), where shear stress is directly proportional to the velocity gradient.

Question 4

Water flows at 2 m/s through a 0.05 m diameter pipe. What is the approximate Reynolds number? (kinematic viscosity ν = 1×10⁻⁶ m²/s)

Accepted Answer

100,000

Answer

Re = VD/ν = 2 × 0.05 / (1×10⁻⁶) = 100,000.

Question 5

The hydraulic radius of a flow cross-section is defined as:

Accepted Answer

The cross-sectional area divided by the wetted perimeter

Answer

Hydraulic radius Rh = A/P, where A is cross-sectional area and P is the wetted perimeter.

NCEES Practice Test

NCEES Practice Test

NCEES Fluid Mechanics 2