Computational Fluid Dynamics Theory & Principles 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 Computational Fluid Dynamics Theory & Principles flashcards as text
Which numerical scheme is known for being unconditionally stable for diffusion problems regardless of time step size?
Answer: Fully implicit (backward Euler)
The fully implicit (backward Euler) scheme is unconditionally stable for diffusion equations, allowing large time steps without numerical instability.
In CFD, the term 'upwinding' refers to:
Answer: Biasing the differencing stencil in the upstream flow direction
Upwinding biases the finite-difference or finite-volume stencil to use information from upstream, stabilizing convection-dominated flows.
The Peclet number in CFD discretization is defined as the ratio of:
Answer: Convective transport rate to diffusive transport rate on the mesh
The cell Peclet number (Pe = u·Δx/ν) compares convective to diffusive transport at the mesh cell level, guiding scheme selection.
Which pressure-velocity coupling algorithm uses a staggered arrangement of pressure and velocity unknowns on separate grids?
Answer: MAC (Marker-and-Cell)
The MAC method, one of the earliest incompressible solvers, stores pressure at cell centers and velocity at cell faces on a staggered grid.
False diffusion in CFD is primarily caused by:
Answer: Flow not aligned with the grid lines in upwind schemes
False (numerical) diffusion in upwind schemes is greatest when flow is oblique to the grid, adding artificial smearing of gradients.
The Von Neumann stability analysis is applicable to:
Answer: Linear PDEs with constant coefficients on uniform Cartesian grids
Von Neumann stability analysis uses Fourier mode decomposition and is strictly valid for linear PDEs with constant coefficients on uniform Cartesian meshes.
In finite element methods for CFD, the Galerkin formulation requires that residuals be orthogonal to:
Answer: The basis (shape) functions
In the standard Galerkin method, the weighted residual is set to zero with test functions chosen equal to the shape functions, enforcing orthogonality of the residual to the function space.