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.
Highlights
Dam breaks can cause rapid floods downstream, with catastrophic consequences in terms of loss of lives and damages of properties and natural habitats, which can be minimized by forecasting the hazards
The dam-break wave propagation usually occurs over a downstream bottom with irregular topography, resulting for example from natural contraction-expansion and meandering of river channels and presence of artificial or natural obstacles
The numerical solutions were obtained with two different approaches, Reynolds-Averaged Navier-Stokes (RANS) and Shallow Water Equations (SWEs), and solved by a Finite-Volume formulation on a structured staggered Finite-Difference grid using VOF for the free surface computation
Summary
Dam breaks can cause rapid floods downstream, with catastrophic consequences in terms of loss of lives and damages of properties and natural habitats, which can be minimized by forecasting the hazards. Due. Water 2020, 12, 1124 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]. Two different symmetrical trapezoidal-shaped and one triangular-shaped obstacles were installed on the side walls to produce an abrupt contraction in the channel cross section. These particular test cases were constructed to examine the influence of topographical contraction on the formation and reflection of the dam-break wave propagating downstream. In a previous work [42] the effect of an abrupt contraction (triangular one) was investigated, through laboratory experiments and numerical RANS simulations. CFD results utilizing VOF-based (RANS) with k-ε turbulence model and SWEs approach, respectively
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