Turbulence without inertia

摘要

In the 1880s Osborne Reynolds established that fluid inertia (that is, momentum) drives the irregular patterns observed in water flowing rapidly from a pipe, plumes emerging from a smokestack, eddies in the wake of a bulky object, and many other everyday phenomena. Known as 'turbulence', these patterns occur at high values of the Reynolds number, the dimensionless ratio of inertial to viscous force. Over the years turbulence has become better characterized, and we now know it to be accompanied not only by an increase in drag, but also by certain characteristic spatial or temporal velocity fluctuations.