Unsteady shallow meandering flows in rectangular reservoirs: a modal analysis of URANS modelling

  • Shallow flows are common in natural and human-made environments. Even for simple rectangular shallow reservoirs, recent laboratory experiments show that the developing flow fields are particularly complex, involving large-scale turbulent structures. For specific combinations of reservoir size and hydraulic conditions, a meandering jet can be observed. While some aspects of this pseudo-2D flow pattern can be reproduced using a 2D numerical model, new 3D simulations, based on the unsteady Reynolds-Averaged Navier-Stokes equations, show consistent advantages as presented herein. A Proper Orthogonal Decomposition was used to characterize the four most energetic modes of the meandering jet at the free surface level, allowing comparison against experimental data and 2D (depth-averaged) numerical results. Three different isotropic eddy viscosity models (RNG k-ε, k-ε, k-ω) were tested. The 3D models accurately predicted the frequency of the modes, whereas the amplitudes of the modes and associated energy were damped for the friction-dominant cases and augmented for non-frictional ones. The performance of the three turbulence models remained essentially similar, with slightly better predictions by RNG k-ε model in the case with the highest Reynolds number. Finally, the Q-criterion was used to identify vortices and study their dynamics, assisting on the identification of the differences between: i) the three-dimensional phenomenon (here reproduced), ii) its two-dimensional footprint in the free surface (experimental observations) and iii) the depth-averaged case (represented by 2D models).

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Metadaten
Author:Daniel ValeroORCiD, Daniel Bernhard BungORCiD, Sebastien Erpicum, Yann Peltier, Benjamin Dewals
DOI:https://doi.org/10.1016/j.jher.2022.03.002
ISSN:1570-6443
Parent Title (English):Journal of Hydro-environment Research
Publisher:Elsevier
Place of publication:Amsterdam
Document Type:Article
Language:English
Year of Completion:2022
Tag:Proper Orthogonal Decomposition; Q-criterion; coherent structures; hydraulic modelling; model performance
Issue:In Press
Link:https://doi.org/10.1016/j.jher.2022.03.002
Zugriffsart:campus
Institutes:FH Aachen / Fachbereich Bauingenieurwesen
collections:Verlag / Elsevier