PHYSICAL AND NUMERICAL MODELLING OF THE MOVABLE BED IN NON-UNIFORM STEEP CHANNELS WITH A SUDDEN NARROWING OR WIDENING

摘要

Experiments have been performed in 8 meter long steep flumes to study the evolution of the bed and the depth of flow especially in case of a sudden narrowing or widening separating two reaches, 15 cm and 30 cm wide. The natural material used had grain sizes ranging from 0.5 mm to over 10 mm. A very short time after the beginning of the flow, a step occurs which is backward-facing along the flow when the flume is widening and forward-facing when it is narrowing. The experimental evolution of the bed is compared with the result of a one-dimensional model coupling hydrodynamic and solid phase equations. An overall good agreement is obtained on the evolution of bed profiles during time as well as on the height of the step.