Analysis — FEA / CFD
Related: finite-element-methods · fluid-mechanics-machinery
Cheat sheet
Formulas
FEA check: Σreactions = Σloads ; mesh convergence of QoI
von Mises for ductile yield indicator; principals for brittle/fatigue
CFD: continuity + Navier–Stokes; y+ for wall turbulence models
CFL stability for explicit transient; residuals monitor convergence
Aero: Cl, Cd, Cm from pressure/shear integration
Mesh independence: monitor KPI vs element size
y+ targets for wall-resolved vs wall-function CFD
Cl, Cd, Cm from pressure/shear integration
Definitions
- QoI
- Quantity of interest — what decision needs
- y+
- Dimensionless wall distance for turbulence wall treatment
- RANS / LES
- Averaged vs large-eddy resolved turbulence approaches
- Mesh independence
- Result stable under refinement
- Validation case
- Compare to experiment/analytic before production runs
- Verification vs validation
- Code solving equations right vs right equations for reality
- Boundary layer
- Critical for aero drag/lift prediction
Topic-wise short notes
Structural FEA
- Linear static → modal → buckling → nonlinear contact progression.
- Bolts/welds idealized — document.
- Report FOS vs Sy with load case description.
CFD & aero tools
- XFLR5/AVL for low-Re aero; CFD for 3D interference.
- Domain size & wake resolution for drag accuracy.
Exam traps & quick notes
- Tools: Ansys, XFLR, SimScale.
- Always show a hand-calc or test-rig sanity check.
- SAE: CFD + XFLR + wind tunnel / dyno / CG balancer.
- Pretty contours ≠ correct — interrogate probes & integrals.
- Compressibility: Ma>0.3 consider density variation.
- Inlets/outlets BC choice dominates CFD outcomes.
Comprehensive notes
Structural FEA
Linear static → buckling/modal as needed; contacts; fatigue screening.
External: Ansys Learning Hub (public blogs) ↗ NAFEMS ↗
CFD & aero tools
Domain size, turbulence model choice, residuals, force monitors; XFLR for lifting surfaces.
External: XFLR5 ↗ NASA CFD resources ↗