Experimental and Numerical Analysis of a Dam-Break Flow through Different Contraction Geometries of the Channel

Abstract

Dam-break wave propagation usually occurs over irregular topography, due for example to natural contraction-expansion of the river bed and to the presence of natural or artificial obstacles. Due to limited available dam-break real-case data, laboratory and numerical modeling studies are significant for understanding this type of complex flow problems. To contribute to the related field, a dam-break flow over a channel with a contracting reach was investigated experimentally and numerically. Laboratory tests were carried out in a smooth rectangular channel with a horizontal dry bed for three different lateral contraction geometries. A non-intrusive digital imaging technique was utilized to analyze the dam-break wave propagation. Free surface profiles and time variation of water levels in selected sections were obtained directly from three synchronized CCD video camera records through a virtual wave probe. The experimental results were compared against the numerical solution of VOF (Volume of Fluid)-based Shallow Water Equations (SWEs) and Reynolds-Averaged Navier-Stokes (RANS) equations with the k-ε turbulence model. Good agreements were obtained between computed and measured results. However, the RANS solution shows a better correspondence with the experimental results compared with the SWEs one. The presented new experimental data can be used to validate numerical models for the simulation of dam-break flows over irregular topography.Water 2020, 12, 1124 2 of 22 to limited available dam-break real-case data [5,6], laboratory and numerical modeling studies are significant for understanding this type of complex flow problems [7][8][9].The analysis of the literature shows several laboratory experiments aimed at investigating the propagation of a dam-break flow over irregular flumes [2,3,[10][11][12][13][14][15][16]. The galloping progresses in the evolution of the imaging technology have led to a wiser use of the digital image processing in laboratory experimental measurements of dam-break flows [17][18][19][20], with significant contribution to better understand the physics of real processes [21,22].Investigation of dam-break flows over complex topography can be performed through numerical analysis and validated through the comparison of numerical solutions obtained with different methods against experimental data [23][24][25][26][27][28]. Most of previous works simulated the dam-break flow through the Shallow Water Equations (SWEs) [2,[29][30][31][32]. The complete 3D Reynolds-Averaged Navier-Stokes (RANS) equations involving the turbulence modeling can more accurately describe the dam-break wave propagation over complex topography [27,28,33,34]. Recently, 3D VOF (Volume of Fluid) based CFD (Computational Fluid Dynamics) modeling software, such as FLOW-3D (Flow-Science Co, New Mexico, NM, USA) have been widely applied to the simulation of unsteady free-surface flows and also tested on dam-break flows [35][36][37][38][39][40].The present research focuses on the dam-break flood wave propagation over the downstream ...

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