Aerodynamics Expert

---
name: aerodynamics-expert
version: 1.0.0
description: Expert-level aerodynamics covering subsonic and supersonic flow, lift and drag, airfoil theory, boundary layers, compressible flow, and CFD methods.
author: luo-kai
tags: [aerodynamics, lift, drag, airfoil, boundary layer, compressible flow, CFD]
---

# Aerodynamics Expert

## Before Starting
1. Subsonic, transonic, or supersonic regime?
2. Internal or external flow?
3. Analysis or design focus?

## Core Expertise Areas

### Airfoil Theory
Lift: generated by pressure difference between upper and lower surfaces.
Camber: curvature of mean line, increases lift at zero angle of attack.
Thickness: affects drag and maximum lift, NACA 4-digit series defines profile.
Angle of attack: increasing AoA increases lift until stall.
Stall: boundary layer separates from suction surface, lift drops suddenly.

### Thin Airfoil Theory
Lift coefficient: CL = 2 pi times alpha for thin symmetric airfoil.
Moment coefficient: CM about quarter chord is zero for symmetric airfoils.
Aerodynamic center: point where moment coefficient is independent of AoA.
Camber effect: adds lift at zero AoA proportional to maximum camber.

### Drag
Pressure drag: form drag from pressure distribution, reduced by streamlining.
Skin friction drag: viscous shear stress on surface, dominant for streamlined bodies.
Induced drag: due to finite wing span, CDi = CL squared over pi AR e.
Wave drag: energy lost to shock waves in transonic and supersonic flow.
Drag polar: CD vs CL squared, slope is 1 over pi AR e.

### Compressible Flow
Mach number: M = V over a, ratio of flow speed to speed of sound.
Critical Mach: freestream Mach where local sonic flow first appears.
Prandtl-Glauert: compressibility correction for subsonic flow, 1 over sqrt 1 minus M squared.
Shock waves: normal and oblique, pressure rises discontinuously.
Expansion fans: isentropic acceleration around convex corners.

## Best Practices
- Verify Reynolds number and Mach number before selecting analysis method
- Use panel methods for subsonic, Euler for transonic, full NS for separated flow
- Validate CFD results against wind tunnel data for critical designs
- Check for flow separation before assuming attached flow methods are valid

## Common Pitfalls
| Pitfall | Fix |
|---|---|
| Applying thin airfoil theory at high AoA | Valid only for small angles, below stall |
| Ignoring compressibility near Mach 0.3 | Apply Prandtl-Glauert correction above M=0.3 |
| 2D analysis for finite wing | Apply finite wing correction for induced drag |
| Inviscid analysis near separation | Use viscous solver for high AoA or bluff bodies |

## Related Skills
- flight-mechanics-expert
- propulsion-expert
- fluid-mechanics-expert