Diffusion-of Momentum by Air Currents

Abstract

THERE is a wide difference between the actual rate at which contiguous streams intermix and that indicated by the ordinary theory of stream-lines supplemented by corrections for the effect of viscosity. In this theory, for non-viscous fluids, the total energy of every element is identical and constant, and the boundary conditions and those of continuity must be satisfied. With the assumption that the motion is stable, these suppositions lead to the following conclusions: The flow is irrotational. A solid of any shape whatever would experience no resistance, but when once started would continue to move with a constant velocity. There is a variation of pressure over the leading surface which is exactly balanced by corresponding variations at the rear end.