CPCE CFD Software & Simulation Techniques 4

Question 1

In CFD, what is 'operator splitting' used for in time integration?

Accepted Answer

Treating different physics operators with separate integration steps

Answer

Decomposing the domain for parallel processing

Answer

Splitting mesh blocks for AMR

Answer

Separating laminar and turbulent contributions

Question 2

What is the key advantage of the Detached Eddy Simulation (DES) approach over pure LES for high-Reynolds-number external flows?

Accepted Answer

DES uses RANS near walls to reduce near-wall mesh cost while using LES away from walls

Answer

DES resolves all scales everywhere in the domain

Answer

DES is always more accurate than LES

Answer

DES eliminates the need for a turbulence model

Question 3

In ANSYS Fluent, which boundary condition type is most appropriate when the total pressure and total temperature at an inlet are known?

Accepted Answer

Pressure inlet

Answer

Velocity inlet

Answer

Mass flow inlet

Answer

Pressure far-field

Question 4

Which numerical scheme is known for its ability to capture shock waves sharply without spurious oscillations in compressible flow simulations?

Accepted Answer

TVD (Total Variation Diminishing) scheme

Answer

Central difference scheme

Answer

Crank-Nicolson scheme

Answer

Pure Galerkin finite element scheme

Question 5

What does 'GCI' (Grid Convergence Index) measure in CFD verification?

Accepted Answer

Discretization error estimate using Richardson extrapolation on multiple mesh levels

Answer

Solver residual reduction per iteration

Answer

Turbulence model uncertainty

Answer

Boundary condition sensitivity

Question 6

In a Volume of Fluid (VOF) simulation for two-phase flow, what does the volume fraction α = 0.5 represent?

Accepted Answer

The interface between two phases

Answer

Pure phase 1

Answer

Pure phase 2

Answer

A phase with 50% density

Question 7

Which parallel decomposition method in OpenFOAM divides the mesh by minimizing inter-processor boundary faces?

Accepted Answer

Scotch decomposition

Answer

Simple decomposition

Answer

Hierarchical decomposition

Answer

Manual decomposition