Resolving energy losses for non-uniform flows in compound channel
D. Bousmar, N. Rivière, S. Proust, A. Paquier (2008)

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Résumé

The aim of this paper is to evaluate the relative weights of three sources of energy loss for non-uniform flows in compound channel: (1) the bed friction; (2) the momentum transfer due to turbulent exchange between the main channel and the floodplains; and (3) the momentum transfer due to mass exchange between the subsections. Energy losses are resolved using a quasi-1D model, namely the Independent Subsections Method (ISM). The ISM computes the water level and the subsection-averaged velocities in the main channel and in the floodplains, simultaneously. This method was tested and validated against experimental measurements in three straight geometries and in eight non-prismatic geometries (skewed floodplains, diverging and converging compound channels). Using the ISM simulations of 46 flows, energy losses due to turbulent exchanges (St), to bed friction (Sf), and to mass exchanges (Sm) are estimated. The relative weights of the dissipation terms at the interfaces between the main channel and the floodplains (St and Sm) and of the mass conservation terms (denoted Ma) are then compared. The results show to what extent the mass conservation and the momentum transfer control the flow depth and the discharge in the floodplain.

Mots clés : chenal, lit, main, messe, conservation-restauration, frottement, conservation, perte d'energie, ecoulement à surface libre, plaine d'inondation, ecoulement en lit compose, compound channel, energy loss, non-uniform flow, momentum transfer, mass conservation