Abstract
During the
propagation of an unsteady open-channel flood wave, its discharge, velocity and
water stage are variable. And these three factors affect each other according
to a complex rule. This paper presents some experimental and theoretical
studies on this phenomenon. Some parameters of the flood wave, such as
discharge, velocity and water depth were measured in a flume system, which is
established for researching the unsteady flow properties. The wave deformation
caused by the unsteadiness of flow was studied. By using the Saint-Venant equation and with some simplifications, expressions
were deduced for the variation of unsteady discharge with water stage. The mechanism
of the asynchronism among discharge, velocity and
water stage, as well as the influence of unsteadiness on the phasic relationship, were analyzed. Furthermore, the loop
phenomenon in the characteristic curve of discharge in open-channel flows was
investigated. The results showed that the comparative loop size was varied with
the changing of the unsteady flow parameter. Based on both the experimental
data and the farther theoretical analysis, the effect of the unsteadiness on
the wave deformation was shown explicitly and the regularity of flood wave
propagation was uncovered preliminary.
Keywords: Unsteady flow, Open channel flow, Rating curve,