Analysis of the transitions between flow patterns in open-channel lateral cavities with increasing aspect ratio

Abstract

The flow pattern within a storage zone governs the efficiency of passive scalar accumulation, spreading and homogenization. The present paper aims at characterizing experimentally the evolution of this flow pattern in a simplified open-channel lateral cavity with twenty increasing horizontal aspect ratio, focusing on the transition between the different flow patterns. Four main flow types are observed and detailed herein with, as the aspect ratio gradually increases: two cells aligned along the main stream axis, one unique cell, two cells aligned transversally and finally a more complex 3D pattern in the second cell. Quantitative characteristics of these cells are extracted from the velocity fields measured in the cavity. A 2D angular momentum balance is then applied that explains the transitions between these flow types and proves to be able to predict the flow patterns reported in the literature.