Optical Propagation and Image Formation Through the Turbulent Atmosphere

Abstract

In contrast with steady flows, also called “laminar flows”, turbulent flows have a random velocity field. In pipes, the transition from laminar to turbulent flows occurs when a dimensionless number, called the Reynolds number, exceeds some value which depends only upon the geometry of the flow. The Reynolds number is defined as ūL/v where ū is the mean flow speed, L is the transverse size of the pipe, and v is the kinematic viscosity of the fluid. This result still applies to the atmosphere if L is taken as some characteristic size of the flow. Large scale flows such as those occuring in the Earth’s atmosphere are easily turbulent.