Unsteady turbulent properties in negative waves in open channels

Unsteady turbulent properties in negative waves in open channels

In an open channel, a sudden drop in free-surface elevation is associated with the development of a negative wave. While some simple analytical solution is widely described in textbooks, little research was conducted to date on the unsteady turbulence properties beneath negative waves. A series of new physical experiments were conducted in a rectangular channel. The unsteady free-surface profil...

Integral turbulent scales in unsteady rapidly varied open channel flows

Negative surges and unsteady turbulent mixing induced by rapid gate opening in a channel

A negative surge is an unsteady open channel flow characterised by a drop in water surface elevation. In this study, a negative surge generated by the rapid gate opening was investigated experimentally with three types of bed roughness. Both instantaneous free-surface and velocity measurements were performed and the results were ensemble-averaged. The experimental data showed a rapid flow accel...

Waves on unsteady currents

Models for surface gravity wave propagation in the presence of currents often assume the current field to be quasi-stationary, which implies that the absolute wave frequency is time invariant. However, in the presence of unsteady currents or time-varying water depth, linear wave theory predicts a time variation of the absolute wave frequency and wavenumber . Herein, observations of wave frequen...

Negative Surges in Open Channels: Physical and Numerical Modeling

Negative surges can be caused by a sudden change in flow resulting from a decrease in water depth. In the present study, some physical experiments were conducted in a rectangular channel to characterize the unsteady free-surface profile and longitudinal velocity beneath a negative surge propagating upstream. The physical observations showed that, during the first initial instants, the celerity ...