EIT Fluid Mechanics 4

Question 1

A fluid has a dynamic viscosity of 0.8 Pa·s and a density of 800 kg/m³. Its kinematic viscosity is:

Accepted Answer

1×10⁻³ m²/s

Answer

Kinematic viscosity ν = μ/ρ = 0.8/800 = 0.001 m²/s = 1×10⁻³ m²/s.

Question 2

The cavitation number (or cavitation index) is defined as:

Accepted Answer

(P − Pv)/(½ρV²)

Answer

The cavitation number σ = (P − Pv)/(½ρV²) compares net pressure above vapor pressure to dynamic pressure.

Question 3

For flow over a cylinder, the drag coefficient Cd is approximately 1.2 at Re = 10⁴. If the velocity doubles, the drag force changes by a factor of:

Accepted Answer

4

Answer

Drag force F_D = ½ρV²CdA; if Cd remains constant, doubling V quadruples the drag force.

Question 4

Manning's equation for open channel flow gives velocity as V = (1/n)·R_h^(2/3)·S^(1/2). If slope S quadruples while all other parameters remain constant, the flow rate changes by a factor of:

Accepted Answer

2

Answer

Q ∝ S^(1/2); quadrupling S gives Q ∝ √4 = 2, so flow rate doubles.

Question 5

The stream function ψ in 2D incompressible flow automatically satisfies:

Accepted Answer

The continuity equation

Answer

Defining u = ∂ψ/∂y and v = −∂ψ/∂x identically satisfies ∂u/∂x + ∂v/∂y = 0 (continuity).

(EIT) Engineer In Training Certification Practice Test

(EIT) Engineer In Training Certification Practice Test

EIT Fluid Mechanics 4