CPCE CPCE Mesh Generation & Boundary Conditions 1

Question 1

What is the primary advantage of a structured (hexahedral) mesh over an unstructured (tetrahedral) mesh in CFD?

Accepted Answer

It typically yields lower numerical diffusion and higher solver efficiency

Answer

Structured hexahedral meshes align with the flow direction, reducing numerical diffusion and improving solver convergence speed compared to unstructured tetrahedral meshes.

Question 2

What boundary condition is applied at a symmetry plane in a CFD simulation?

Accepted Answer

Zero normal velocity and zero normal gradients of all other variables

Answer

A symmetry boundary sets the normal velocity component to zero and enforces zero normal gradients of scalar variables, effectively mirroring the flow without resolving the full domain.

Question 3

What is the purpose of mesh refinement in the boundary layer region of a CFD simulation?

Accepted Answer

To accurately resolve large velocity gradients and capture wall shear stress

Answer

Boundary layer mesh refinement (small cells near walls) is needed to resolve steep velocity gradients in the viscous sublayer and accurately predict wall shear stress and heat transfer.

Question 4

In CFD, what does 'mesh skewness' measure and why is it important?

Accepted Answer

The deviation of a cell's shape from an ideal equilateral form, affecting solution accuracy

Answer

Mesh skewness quantifies how much a cell deviates from an ideal shape; highly skewed cells degrade interpolation accuracy and can cause solver divergence.

Question 5

What type of boundary condition is a 'velocity inlet' in CFD, and what quantities must typically be specified?

Accepted Answer

An inlet condition requiring velocity vector, turbulence intensity, and turbulence length scale

Answer

A velocity inlet requires specifying the velocity magnitude and direction, plus turbulence quantities (intensity and length scale or equivalent) to fully define the incoming flow state.

(CPCE) Certified Professional CFD Engineer Practice Test

(CPCE) Certified Professional CFD Engineer Practice Test

CPCE CPCE Mesh Generation & Boundary Conditions 1