CPCE Fluid Flow & Heat Transfer Analysis 3

Question 1

In CFD mesh generation, what is the primary advantage of a structured hexahedral mesh over an unstructured tetrahedral mesh?

Accepted Answer

Lower numerical diffusion and better convergence

Answer

Hexahedral structured meshes produce lower numerical diffusion due to their alignment with flow direction and better convergence behavior in CFD solvers.

Question 2

What does the Courant-Friedrichs-Lewy (CFL) condition limit in transient CFD simulations?

Accepted Answer

Time step size relative to convective transport

Answer

The CFL condition requires that the time step be small enough that information does not travel more than one cell width per time step, ensuring numerical stability.

Question 3

In natural convection problems, which dimensionless number determines the flow regime and heat transfer rate?

Accepted Answer

Rayleigh number

Answer

The Rayleigh number (Ra = Gr × Pr) characterizes natural convection and determines whether flow is laminar or turbulent in buoyancy-driven problems.

Question 4

What type of CFD simulation approach resolves all turbulent length and time scales without any turbulence modeling?

Accepted Answer

Direct Numerical Simulation (DNS)

Answer

DNS resolves the complete range of turbulent scales from the Kolmogorov microscales to the integral length scales, requiring no turbulence model but enormous computational resources.

Question 5

In a CFD simulation of conjugate heat transfer, what is solved simultaneously?

Accepted Answer

Fluid flow and solid conduction heat transfer

Answer

Conjugate heat transfer CFD simulations simultaneously solve the fluid energy equation in flow regions and the heat conduction equation in solid regions.

(CPCE) Certified Professional CFD Engineer Practice Test

(CPCE) Certified Professional CFD Engineer Practice Test

CPCE Fluid Flow & Heat Transfer Analysis 3