CFD Software & Simulation Techniques Flashcards
7 cards from real CPCE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 CFD Software & Simulation Techniques flashcards as text
In CFD, what is 'operator splitting' used for in time integration?
Answer: Treating different physics operators with separate integration steps
Operator splitting (e.g., Strang splitting) integrates different physics terms (advection, diffusion, source) in separate sub-steps, allowing use of optimal schemes for each.
What is the key advantage of the Detached Eddy Simulation (DES) approach over pure LES for high-Reynolds-number external flows?
Answer: DES uses RANS near walls to reduce near-wall mesh cost while using LES away from walls
DES is a hybrid method that applies RANS in attached boundary layers (where full LES is prohibitively expensive) and LES in separated regions where large eddies dominate.
In ANSYS Fluent, which boundary condition type is most appropriate when the total pressure and total temperature at an inlet are known?
Answer: Pressure inlet
The pressure inlet boundary condition in Fluent accepts total (stagnation) pressure and temperature, making it appropriate when those quantities are known at the inlet.
Which numerical scheme is known for its ability to capture shock waves sharply without spurious oscillations in compressible flow simulations?
Answer: TVD (Total Variation Diminishing) scheme
TVD schemes apply flux limiters to suppress oscillations near discontinuities (shocks) while maintaining high-order accuracy in smooth flow regions.
What does 'GCI' (Grid Convergence Index) measure in CFD verification?
Answer: Discretization error estimate using Richardson extrapolation on multiple mesh levels
GCI provides a quantitative estimate of discretization error by applying Richardson extrapolation to solutions on systematically refined meshes.
In a Volume of Fluid (VOF) simulation for two-phase flow, what does the volume fraction α = 0.5 represent?
Answer: The interface between two phases
In VOF, α = 0 and α = 1 represent pure phases, while intermediate values (including 0.5) mark the interfacial region where both phases coexist in a cell.
Which parallel decomposition method in OpenFOAM divides the mesh by minimizing inter-processor boundary faces?
Answer: Scotch decomposition
Scotch decomposition uses graph partitioning to minimize the number of inter-processor boundaries, reducing communication overhead in parallel simulations.