Prandtl's theory of the 3D wing of large aspect ratio. Induced drag.
The Trefftz plane. The model as an asymptotic result.

Virtual mass in two and three dimensions. D'Alembert's paradox revisited.

Begin discussion of Newtonian viscous fluids.

**Suggested reading:**

- Batchelor 444-449, 583-591
- L & L 26-30