scholarly journals A New Experimental Study and SPH Comparison for the Sequential Dam-Break Problem

2020 ◽  
Vol 8 (11) ◽  
pp. 905
Author(s):  
Selahattin Kocaman ◽  
Kaan Dal
Keyword(s):  
Image Processing ◽  
Numerical Models ◽  
Flow Behavior ◽  
Rectangular Channel ◽  
Numerical Results ◽  
Dam Break ◽  
Frame Rate ◽  
Image Processing Technique ◽  
Complex Flow ◽  
The Impact

The floods following the event of a dam collapse can have a significant impact on the downstream environment and ecology. Due to the limited number of real-case data for dam-break floods, laboratory experiments and numerical models are used to understand the complex flow behavior and to analyze the impact of the dam-break wave for different scenarios. In this study, a newly designed experimental campaign was conducted for the sequential dam-break problem in a rectangular channel with a steep slope, and the obtained results were compared against those of a particle-based numerical model. The laboratory tests permitted a better understanding of the physical process, highlighting five successive stages observed in the downstream reservoirs: dam-break wave propagation, overtopping, reflection wave, run-up, and oscillations. Experimental data were acquired using a virtual wave probe based on an image processing technique. A professional camera and a smartphone camera were used to obtain the footage of the experiment to examine the effect of the resolution and frame rate on image processing. The numerical results were obtained through the Smoothed Particle Hydrodynamics (SPH) method using free DualSPHysics software. The experimental and numerical results were in good agreement generally. Hence, the presented data can be used as a benchmark in future studies to validate the SPH and other Computational Fluid Dynamics (CFD) methods.

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

Water ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 1124 ◽  
Author(s):  
Selahattin Kocaman ◽  
Hasan Güzel ◽  
Stefania Evangelista ◽  
Hatice Ozmen-Cagatay ◽  
Giacomo Viccione
Keyword(s):  
Wave Propagation ◽  
Numerical Models ◽  
Rectangular Channel ◽  
Dam Break ◽  
Water Levels ◽  
Experimental Results ◽  
Complex Flow ◽  
Related Field ◽  
Dam Break Flow ◽  
Irregular Topography

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.

scholarly journals Optimizing Laboratory Investigations of Saline Intrusion by Incorporating Machine Learning Techniques

Water ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2996
Author(s):  
Georgios Etsias ◽  
Gerard A. Hamill ◽  
Eric M. Benner ◽  
Jesús F. Águila ◽  
Mark C. McDonnell ◽  
...  
Keyword(s):  
Machine Learning ◽  
Image Processing ◽  
Porous Medium ◽  
Glass Bead ◽  
Machine Learning Algorithms ◽  
Machine Learning Techniques ◽  
Image Processing Technique ◽  
Saline Intrusion ◽  
Learning Techniques ◽  
The Impact

Deriving saltwater concentrations from the light intensity values of dyed saline solutions is a long-established image processing practice in laboratory scale investigations of saline intrusion. The current paper presents a novel methodology that employs the predictive ability of machine learning algorithms in order to determine saltwater concentration fields. The proposed approach consists of three distinct parts, image pre-processing, porous medium classification (glass bead structure recognition) and saltwater field generation (regression). It minimizes the need for aquifer-specific calibrations, significantly shortening the experimental procedure by up to 50% of the time required. A series of typical saline intrusion experiments were conducted in homogeneous and heterogeneous aquifers, consisting of glass beads of varying sizes, to recreate the necessary laboratory data. An innovative method of distinguishing and filtering out the common experimental error introduced by both backlighting and the optical irregularities of the glass bead medium was formulated. This enabled the acquisition of quality predictions by classical, easy-to-use machine learning techniques, such as feedforward Artificial Neural Networks, using a limited amount of training data, proving the applicability of the procedure. The new process was benchmarked against a traditional regression algorithm. A series of variables were utilized to quantify the variance between the results generated by the two procedures. No compromise was found to the quality of the derived concentration fields and it was established that the proposed image processing technique is robust when applied to homogeneous and heterogeneous domains alike, outperforming the classical approach in all test cases. Moreover, the method minimized the impact of experimental errors introduced by small movements of the camera and the presence air bubbles trapped in the porous medium.

scholarly journals On Dam-Break Flow Routing in Confluent Channels

2019 ◽  
Vol 16 (22) ◽  
pp. 4384
Author(s):  
Sihan Chen ◽  
Yingjin Li ◽  
Zhong Tian ◽  
Qiang Fan
Keyword(s):  
Flow Field ◽  
Arrival Time ◽  
Processing Technique ◽  
Surface Flow ◽  
Dam Break ◽  
Image Processing Technique ◽  
Physical Experiments ◽  
Dam Break Flow ◽  
The Impact ◽  
Motion Images

The flood propagation at a confluence of channels exhibits a unique routing pattern, while there are few studies on the routing of dam-break flow in confluent channels. In this study, we conducted physical experiments and a numerical simulation to investigate the influence of different confluence angles on the routing of a dam-break flood. Experiments were carried out in smooth, transparent, rectangular prismatic channels to study the dam-break flow under four different confluence angles. The flow velocity was measured using an image processing technique, and the surface flow field was effectively captured by synchronously recording the particle motion images. Based on the variation of the water level and flow discharge, as the confluence angle increased, the retardation and abatement effects on the flood increased. Specifically, the flood arrival time was delayed by approximately 0.91% to 21.18%, and the peak flood discharge was reduced by approximately 9.05% to 58.36%. Combined with the surface flow field at the confluence and in the downstream sections, as the confluence angle increased, the impact points at the confluence and in the downstream straight sections moved upward, and the impact range was reduced. Combined with the pressure variation pattern, the routing of dam-break flow in the confluent channels experienced a process of impact-reflection-return-attenuation.

scholarly journals Spectral-Element Simulation of the Turbulent Flow in an Urban Environment

2021 ◽  
Author(s):  
Maxime Stuck ◽  
Alvaro Vidal ◽  
Pablo Torres ◽  
Hassan M. Nagib ◽  
Candace Wark ◽  
...  
Keyword(s):  
Turbulent Flow ◽  
Urban Environment ◽  
Good Description ◽  
Flow Behavior ◽  
Flow Characteristics ◽  
Mean Flow ◽  
Complex Flow ◽  
Turbulence Statistics ◽  
Experimental Database ◽  
The Impact

The mean flow and turbulence statistics of the flow through a simplified urban environment, which is an active research area in order to improve the knowledge of turbulent flow in cities, is investigated. This is useful for civil engineering, pedestrian comfort and for health concerns caused by pollutant spreading. In this work, we provide analysis of the turbulence statistics obtained from well-resolved large-eddy simulations (LES). A detailed analysis of this database reveals the impact of the geometry of the urban array on the flow characteristics and provides for a good description of the turbulent features of the flow within a simplified urban environment. The most prominent features of this complex flow include coherent vortical structures such as the so-called arch vortex, the horseshoe vortex and the roof vortex. These structures of the flow have been identified by an analysis of the turbulence statistics. The influence of the geometry of the urban environment (and particularly the street width and the building height) on the overall flow behavior have also been studied. Finally, the well-resolved LES results were compared with the experimental database from Monnier et al. to discuss differences and similarities between the respective urban configurations.

scholarly journals Comparative Analysis of Building Representations in TELEMAC-2D for Flood Inundation in Idealized Urban Districts

Water ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1840 ◽  
Author(s):  
Li ◽  
Liu ◽  
Mei ◽  
Shao ◽  
Wang ◽  
...  
Keyword(s):  
Laboratory Experiments ◽  
Numerical Models ◽  
Flood Inundation ◽  
Complex Flow ◽  
Urban Flood ◽  
Urban Districts ◽  
Mesh Resolution ◽  
Flood Simulations ◽  
The Impact ◽  
Better Than

This study aims to better understand the impact of different building representations and mesh resolutions on urban flood simulations using the TELEMAC-2D model in idealized urban districts. A series of numerical models based on previous laboratory experiments was established to simulate urban flooding around buildings, wherein different building layouts (aligned and staggered) were modeled for different building representations: building–hole (BH), building–block (BB), and building–resistance (BR) methods. A sensitivity analysis of the Manning coefficient for building grids indicated that the unit-width discharge and water depth in building grids reduce as the Manning coefficient is less than 104 m-1/3⋅s. The simulated depths via the BH, BB, and BR methods were compared with the measured data in terms of three accuracy indicators: root mean square error, Pearson product–moment correlation coefficient, and Nash–Sutcliffe efficiency. Observing apparent discrepancies based on the hydrographs was difficult; however, some slight distinctions were observed based on the aforementioned three indicators. The sensitivity of 1, 2, and 5 cm mesh resolutions was also analyzed: results obtained using 1 cm resolution were better than those obtained using other resolutions. The complex flow regime around buildings was also investigated based on mesh resolution, velocity, and Froude number according to our results. This study provides key data regarding urban flood model benchmarks, focusing on the effect of different building representations and mesh resolutions.

Complex Flow Dynamics in Dense Granular Flows—Part I: Experimentation

2005 ◽  
Vol 73 (4) ◽  
pp. 648-657 ◽  
Author(s):  
Piroz Zamankhan ◽  
Mohammad Hadi Bordbar
Keyword(s):  
Flow Behavior ◽  
Viscoelastic Behavior ◽  
Granular Flows ◽  
Viscous Damping ◽  
Complex Flow ◽  
Interparticle Interactions ◽  
Dynamic Simulations ◽  
Newton’S Cradle ◽  
The Impact ◽  
Dense Granular Flows

By applying a methodology useful for analysis of complex fluids based on a synergistic combination of experiments, computer simulations, and theoretical investigation, a model was built to investigate the fluid dynamics of granular flows in an intermediate regime where both collisional and frictional interactions may affect the flow behavior. In Part I, the viscoelastic behavior of nearly identical sized glass balls during a collision have been studied experimentally using a modified Newton’s cradle device. Analyzing the results of the measurements, by employing a numerical model based on finite element methods, the viscous damping coefficient was determined for the glass balls. Power law dependence was found for the restitution coefficient on the impact velocity. In order to obtain detailed information about the interparticle interactions in dense granular flows, a simplified model for collisions between particles of a granular material was proposed to be of use in molecular dynamic simulations, discussed in Part II.

An image processing technique for measuring free surface of dam-break flows

2010 ◽  
Vol 50 (3) ◽  
pp. 665-675 ◽  
Author(s):  
Francesca Aureli ◽  
Andrea Maranzoni ◽  
Paolo Mignosa ◽  
Chiara Ziveri
Keyword(s):  
Image Processing ◽  
Free Surface ◽  
Processing Technique ◽  
Dam Break ◽  
Image Processing Technique
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