Physical and numerical modeling of overbank flow with a groyne on the floodplain
A. Bourdat, N. Rivière, Y. Peltier, S. Proust, F. Thollet, A. Paquier (2008)

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Résumé

This paper focuses on both physical and numerical modeling of flow in the vicinity of a groyne, blocking off the floodplain of an asymmetric compound channel, and perpendicular to the main flow direction. Experiments were conducted in a laboratory flume and in a small-scale model. Various lengths of groyne d were used in both the laboratory flume and the small-scale model. Water levels, ve-locity field and spreading of the recirculation zone behind the obstacle were measured for five flow configurations. The influence on the flow parameters of aspect ratio d/B (where B is the total width of the channel), of total discharge Q and of relative depth ratio hr were examined. Particularly, a hydraulic disjunction may occur between the subcritical flow and the supercritical flow respectively located up-stream and immediately downstream the obstacle, depending on the values of discharge Q and aspect ratio d/B. Flows were simulated with the 2D-H program RUBAR 20 (Cemagref). Two simple turbu-lence closures that are often used by engineers were tested: a constant eddy viscosity and the Elder's model u*, h. Simulations are compared to experimental measurements, focusing on the streamwise profiles of water level and discharge distribution across the channel, and on the spreading of the recir-culation zone. The influence of the turbulence model on flow parameters is then investigated.

Mots clés : chenal, main, modèle réduit, eau, acculturation, remblai, simulation, influence, aspect, lit majeur, modele numerique, ecoulement, canal experimental, simulation numérique, modele bidimensionnel, compound channel, groyne, recirculation zone, physical modeling, 2d-h modeling