Aerodynamics at the Particle Level

This paper is intended to clarify some of the rather well-known aerodynamic phenomena. It is also intended to pique the interest of the layman as well as the professional. All aerodynamic forces on a surface are caused by collisions of fluid particles with the surface. While the standard approach to fluid dynamics, which is founded on the fluid approximation, is effective in providing a means of calculating various behavior and properties, it begs the question of causality. The determination of the causes of many of the most important aerodynamic effects requires a microscopic examination of the fluid and of the surface with which it interacts. The Kutta-Joukowski theorem is investigated from first physical principles. It is noted that the circulation does not arise alone as a physical phenomenon, e.g. air doesn't flow forward under a wing, but must be added to the translation flow. The circulation term is necessary to take into account the vertical deflection of the air flow by a wing. Various aerodynamic devices are discussed, e.g. rocket engine exhaust diffuser and the perfume atomizer. The section on slurries discusses pyroclastic flow as occurs in violent volcanic eruptions.