Intermittency in Large-Scale Turbulent Flows

Abstract

Observations show that high levels of fluctuations occur sporadica lly in bursts in flows at high Reynolds number. The bursts of turbulence seem to be bursts of gene ration of turbulence involving a hierarchy of scales within a b urst with in­ tensive excbange of energy between scales of motion. The net transfer of energy through the cascade of scales appears to be almost discontinuous in space and time, with transfers over small ranges in scale being imbedded within regions of larger-scale transport. In recent years, we have come closer to an understanding of the properties of energy cascades and intermittency in turbulence. Here, as in every field of science, ideas are suggested based on varying degrees of complete­ ness of physical insight. Other workers take such suggestions and pursue them further, developing formal approximations and models that predict the structure of certain measures of turbulent flows. In turbulence, we are often torn between a desire for detailed description of the physics and a desire for more elegant and