Introduction to CFD & its Application

A: Governing principle: Reynolds number compares inertial to viscous forces using characteristic length and dynamic viscosity. Applied here: Re = ρVD/μ = (1.2×5×0.05)/(1.8e-5) ≈ 1.7e4, which sits near the laminar–turbulent transition for internal flow. Distractor B traps engineers who switch to ν without changing the formula, a common slip when jumping between CFD solvers.

A: Governing principle: Courant number Co = VΔt/Δx and controls information travel per time step. Applied here: Co = 30×1e-4 / 0.002 = 1.5, already aggressive unless the solver is implicit. Distractor D catches people who think relaxation changes physics rather than numerical stability limits.

A: Governing principle: turbulence model choice trades accuracy in adverse pressure gradients against cost. Applied here: k–ω SST handles separation better than k–ε without LES-level mesh and time-step demands. Distractor D tempts aerospace-trained engineers who forget wall resolution requirements when wall functions are off.

A: Governing principle: validation measures how well the model represents reality for a defined application. Applied here: ASME V&V 20 focuses on uncertainty quantification, not curve fitting or test elimination. Distractor B attracts analysts who confuse calibration with validation under schedule pressure.