The kinematic structure of open-channel flows

Abstract

1. Flow turbulence. Turbulent eddy formations exert a substantial influence on the kinematic structure of openchannel flows. 2. Analysis of the field-based and experimental data that have been discussed here, which are the result of studies performed by numerous researchers as well as the present authors, persuasively demonstrate the presence of a formation of transverse eddies both in the central part of the flow as well as near the lateral walls. The formation is responsible for the distribution of the longitudinal flow rates along the length of a uniform turbulent flow. 3. It may be assumed that an eddy will arise in the zone located between the free surface and the lateral wall which is directed opposite to the eddy of the free surface (Figs. 1, 2, and 3). In the central part of the channel this will lead to twisting of the isotachs in the direction of the free surface, while in the area of the lateral walls, twisting in the direction of the slopes. This patterns occurs both in simple as well as in compound channels (Figs. 4 and 7). 4. There is a need for exhaustive investigations of the characteristics of the turbulent regime, and the conditions under which transverse turbulent eddy formations arise and affect the development of the longitudinal flow rates and their distribution across the width of the flow. Such investigations would be helpful in studying the kinematic structure of flow when attempting to estimate the conveyance capacity of currents, the stability of channel beds, and load transport. 4. Currently known dependences for describing the distribution of the averaged local flow rates do not adequately reflect the true picture in the most critical portion of a current — i.e., in the sloping portion. It is this portion which determines the conditions of stability of deformed channels of rivers and canals.