Fluid Flow & Heat Transfer Analysis 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 Fluid Flow & Heat Transfer Analysis flashcards as text
In CFD mesh generation, what is the primary advantage of a structured hexahedral mesh over an unstructured tetrahedral mesh?
Answer: Lower numerical diffusion and better convergence
Hexahedral structured meshes produce lower numerical diffusion due to their alignment with flow direction and better convergence behavior in CFD solvers.
What does the Courant-Friedrichs-Lewy (CFL) condition limit in transient CFD simulations?
Answer: Time step size relative to convective transport
The CFL condition requires that the time step be small enough that information does not travel more than one cell width per time step, ensuring numerical stability.
In natural convection problems, which dimensionless number determines the flow regime and heat transfer rate?
Answer: Rayleigh number
The Rayleigh number (Ra = Gr × Pr) characterizes natural convection and determines whether flow is laminar or turbulent in buoyancy-driven problems.
What type of CFD simulation approach resolves all turbulent length and time scales without any turbulence modeling?
Answer: Direct Numerical Simulation (DNS)
DNS resolves the complete range of turbulent scales from the Kolmogorov microscales to the integral length scales, requiring no turbulence model but enormous computational resources.
In a CFD simulation of conjugate heat transfer, what is solved simultaneously?
Answer: Fluid flow and solid conduction heat transfer
Conjugate heat transfer CFD simulations simultaneously solve the fluid energy equation in flow regions and the heat conduction equation in solid regions.
Which finite volume discretization scheme is second-order accurate in space and centered in nature?
Answer: Central differencing scheme
The central differencing scheme evaluates face values as arithmetic averages of neighboring cell values, yielding second-order spatial accuracy but prone to instability at high Peclet numbers.
For flow over a cylinder, at what approximate Reynolds number does the von Kármán vortex street first appear?
Answer: Re ≈ 40
Von Kármán vortex shedding begins at approximately Re ≈ 40-50 when the symmetric steady wake becomes unstable and alternating vortices are shed.