Introduction

Real flows are usually classified into the two categories of laminar flow and turbulent flow. Because almost all geophysical flows are turbulent, one of the most important topics in hydraulics and fluid mechanics is a clarification of the structure of turbulence and the associated transport of momentum, heat and mass. A general theoretical solution for turbulent flows has not been obtained because the governing equations of turbulence, the Navier-Stokes equations, have both non-linear and chaotic features.