Flowing Water, Turbulent and Laminar Flows

Abstract

This chapter reviews laminar and turbulent flows in the context of flowing waters. It starts with the examinations of balances of forces and introduces the concept of Reynolds averaging for turbulent flows. These are followed by outlines of the basic methods of modeling, which are based on the Boussinesq hypothesis and different assumptions about turbulent viscosity. Turbulence modeling for flowing waters is illustrated by examining generic turbulent flows: boundary layer, mixing layer, jet and wake. Predictions of turbulence modeling are compared to the results of field-based experiments completed on natural rivers. Although the turbulent flows in flowing waters are always considered difficult to understand and predict, the knowledge of these flows has greatly advanced during past decades and can be used for coupling abiotic and biotic factors in complex ecological models.