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

IF 2.4 3区 环境科学与生态学 Q2 ENGINEERING, CIVIL
Daniel Valero , Daniel B. Bung , Sebastien Erpicum , Yann Peltier , Benjamin Dewals
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引用次数: 0

Abstract

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).

矩形水库中的非定常浅曲流——URANS模型的模态分析
浅水流在自然和人为环境中都很常见。即使是简单的矩形浅储层,最近的实验室实验表明,发展中的流场也特别复杂,涉及大规模湍流结构。对于油藏规模和水力条件的特定组合,可以观察到曲流射流。虽然这种伪二维流型的某些方面可以使用二维数值模型再现,但基于非定常reynolds - average Navier-Stokes方程的新的三维模拟显示出本文所述的一致优势。采用正交分解法对自由表面上的四种最高能量模式进行了表征,并与实验数据和二维(深度平均)数值结果进行了比较。测试了三种不同的各向同性涡旋粘度模型(RNG k-ε、k-ε、k-ω)。三维模型准确地预测了模态的频率,而模态的振幅和相关能量在摩擦占主导地位的情况下被阻尼,而在非摩擦情况下被增强。三种湍流模型的性能基本相似,在雷诺数最高的情况下,RNG k-ε模型的预测效果略好。最后,使用q准则识别漩涡并研究其动力学,帮助识别以下三者之间的差异:i)三维现象(此处再现),ii)其在自由表面的二维足迹(实验观测)和iii)深度平均情况(由2D模型表示)。
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来源期刊
Journal of Hydro-environment Research
Journal of Hydro-environment Research ENGINEERING, CIVIL-ENVIRONMENTAL SCIENCES
CiteScore
5.80
自引率
0.00%
发文量
34
审稿时长
98 days
期刊介绍: The journal aims to provide an international platform for the dissemination of research and engineering applications related to water and hydraulic problems in the Asia-Pacific region. The journal provides a wide distribution at affordable subscription rate, as well as a rapid reviewing and publication time. The journal particularly encourages papers from young researchers. Papers that require extensive language editing, qualify for editorial assistance with American Journal Experts, a Language Editing Company that Elsevier recommends. Authors submitting to this journal are entitled to a 10% discount.
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