CFD Post-Processing, Validation & Verification 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 Post-Processing, Validation & Verification flashcards as text
In CFD post-processing, what does a streamline represent?
Answer: A line tangent to the velocity vector field at every point at a given instant
A streamline is a curve that is instantaneously tangent to the velocity vector at every point, representing the direction of flow at a specific time instant.
Which metric is used to assess spatial discretization error in CFD by comparing solutions on systematically refined grids?
Answer: Grid Convergence Index (GCI)
The Grid Convergence Index (GCI) is the standard metric recommended by ASME and AIAA to quantify spatial discretization uncertainty using Richardson extrapolation across refined grids.
What is the primary purpose of a Q-criterion isosurface in CFD post-processing?
Answer: To identify and visualize vortical structures in the flow
The Q-criterion identifies vortices by locating regions where the rotation rate tensor dominates the strain rate tensor (Q > 0), making it useful for visualizing coherent vortical structures.
In verification and validation (V&V) of CFD, 'verification' specifically refers to:
Answer: Ensuring the numerical algorithm correctly solves the governing equations
Verification confirms that the mathematical model is solved correctly — i.e., the numerical implementation is free of coding errors and discretization converges — without regard to whether the model represents reality.
When monitoring residuals during a steady-state CFD simulation, which condition best indicates convergence?
Answer: Residuals plateau at a constant non-zero value and key monitor quantities stabilize
True convergence in steady-state CFD is indicated when residuals have leveled off (not necessarily at machine precision) and engineering quantities of interest such as drag, lift, or mass flow rate have stabilized.
In CFD results, a non-dimensionalized wall distance y+ ≈ 1 is required when using:
Answer: Low-Reynolds-number turbulence models that resolve the viscous sublayer
Low-Reynolds-number turbulence models and wall-resolved LES require y+ ≈ 1 to accurately capture the viscous sublayer without relying on wall-function approximations.
Which technique is used to extract a force coefficient (e.g., drag coefficient) from a CFD solution?
Answer: Integrating pressure and viscous stress over the body surface and normalizing by dynamic pressure and reference area
Drag coefficient is obtained by integrating both pressure forces and viscous (shear) forces over the body surface, then dividing by the product of the reference dynamic pressure and reference area.