Author(s): Tobias Meile; Jean-Louis Boillat; Anton J. Schleiss
Keywords: Flow resistance; hydraulic model; macro-roughness; surge wave experiment; unsteady channel flow
Abstract: Surge waves from upstream have been studied systematically in a 40 m long channel. Its banks were equipped with large-scale rectangular roughness elements. In addition to a prismatic reference channel, 41 different configurations of rectangular bank cavities have been investigated. The purpose was to study the effect of large-scale bank roughness on steady and unsteady flows. The macro-roughness of the channel banks increases the flow resistance. Consequently, the absolute celerity of the surge wave front is also reduced by between 5 and 25%. Based on the concept of an effective channel width for the computation of the mean flow velocity, the relative celerity of the surge wave can be predicted for macro-rough channel configurations. The attenuation of the wave front height is increased by the macro-rough flow resistance as well as by the partial reflections of the surge waves in the cavities and passive retention of the latter.