ABSTRACT
Turbulent flows at relatively high Reynolds numbers are characterized by extremely irregular fluctuations in velocity, temperature, pressure, and other properties. Turbulent flows are characterized by eddies and vortices. Chunks of fluid covering a wide size range move randomly around with respect to the mean flow. The structure of the boundary layer in fully turbulent flow is similar in internal and external flows. Turbulence fluctuations make the analysis of turbulent flow based on local and instantaneous Navier–Stokes equations extremely time consuming, even with fast computers. In an isotropic turbulent field, the statistically averaged properties are invariant under the rotation of the coordinate system, or under reflection with respect to a coordinate plane. Kolmogorov’s theory of isotropic turbulence, proposed in early 1940s, provides a powerful and useful framework for modeling the behavior of turbulent eddies that are much smaller than the largest eddy scales in a highly turbulent flow field.
