Influence des contraintes turbulentes dans un écoulement à lit composé : implémentation du modèle k-epsilon

Details

Supervisors

Soares Frazao, Sandra ; Bousmar, Didier

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil des constructions, à finalité spécialisée

Abstract

enWhen a natural river floods, its discharge increases, resulting in an increase in water level. This can cause the river to overflow its banks and occupy the floodplains. This type of flow, called compound flow, can threaten the infrastructures present near the watercourse. Since the flow velocity is generally lower on the floodplains occupied by denser vegetation, a shear surface appears at the interface between the main channel and the floodplains and induces vertical axis vortices. These vortices are the source of non-negligible momentum exchange. We notice that if we do not take into account this phenomenon in the flow model, the numerical simulations seem incomplete. The objective of this work is to implement the two-dimensional k-epsilon model which allows to take into account these additional stresses which arise mainly at the interfaces of the different subsections of the compound bed flow. To do this, this turbulent stress model is introduced into the SDFlow2D computational code which solves the two-dimensional Saint-Venant equations using a finite volume method on unstructured meshes. The latter allows to perform numerical simulations for different test cases. The efficiency of the model as well as the different modeling parameters can then be discussed. This work shows that the k-epsilon turbulent stress model correctly reproduces the momentum exchange induced by the turbulent structures that appear at the shear surfaces. Thus, the velocity profile is less steep and more diffusive than a model that does not take into account the turbulent constraints. This model does not bring anything more than the k-l model which is a simplification.