Linear Analysis of Shallow Water Wave Propagation in Open Channels

Flood wave movement in an open channel can be treated as disturbances imposed at the upstream and downstream boundaries of a channel to an initially steady uniform flow. Linearized, cross sectionally integrated continuity and momentum equations are introduced to describe one-dimensional, unsteady, gradually varied flow in open channels. The Laplace transform method is adopted to obtain first-order analytical spatio-temporal expressions of upstream and downstream channel response functions. These expressions facilitate a critical comparison among different wave approximations in terms of their mathematical properties and physical characteristics. One or two families of characteristic waves, parameterized by an attenuation factor and a wave celerity, are found for various wave approximations. The effects of the downstream boundary condition on different wave approximations are discussed and compared. Wave translation, attenuation, reflection, distortion, and configuration from the analyses are further investigated and interpreted; thus, the differences and similarities in the propagating mechanism among the various wave approximations are revealed.