Special Issue "Physical Modelling in Hydraulics Engineering"

A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Hydraulics and Hydrodynamics".

Deadline for manuscript submissions: closed (15 February 2021).

Special Issue Editors

Prof. Dr. Enrique Peña-González
E-Mail Website
Guest Editor
Centre for Technological Innovations in Construction and Civil Engineering (CITEEC), University of A Coruña, Galicia 15001, Spain
Interests: coastal hydraulics; fluvial hydraulics; port operability
Dr. Jose Anta Alvarez
E-Mail Website
Guest Editor
Centre for Technological Innovations in Construction and Civil Engineering (CITEEC), University of A Coruña, Galicia 15001, Spain
Interests: urban hydrology; runoff and wash-off processes; sewer sediments; combined sewer overflows; imaging techniques
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

In recent years, the application of physical modeling in hydraulic engineering has experienced an increasing progress due to several factors, such as (i) the development of new large-scale models, which allows analyzing and simulating different processes in controlled environments under close-to-reality conditions, (ii) the development of new measurement techniques, such as imaging techniques or the application of low-cost technologies, and (iii) a change in the vision of hydraulic engineering that is now more closely connected with other areas of knowledge linked to water quality, ecosystemic services or the social perception of traditional engineering works. These factors, together with other societal challenges such as climate change, population growth or the digitalization of the water sector, have led to a paradigm shift in the development of physical models in the field of hydraulic engineering.

This Special Issue aims to cover the main relevant physical modeling approaches related with hydraulics engineering, including hydraulic structures, fluvial, coastal, transition zones, urban, and ecosystems. All contributions are welcomed, including innovative solutions for common aspects in nature and infrastructures, coming from both basic and applied research. Topics regarding novel instrumentation and application of usual devices to new developments, real case studies, and adaptation to climate change scenarios are especially welcomed. Other topics covered in the Special Issue are nature-based solutions both for environment to urban locations, and studies with comparison with numerical modeling for its calibration, as increasing field of interest. Tentative papers are intended to deeply describe the materials and methods used in the physical modeling, scale effects, and accuracy of the measurements to validate the results.

We await your contributions for this Special Issue of Water, with an attractive impact factor and dissemination worldwide in the scientific community.

Prof. Dr. Enrique Peña-González
Dr. Jose Anta Alvarez
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Water is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Physical modeling
  • Hydraulic structures
  • Fluvial hydraulics
  • Coastal hydraulics
  • Urban hydrology
  • Ecosystems
  • Innovative facilities and instrumentation

Published Papers (20 papers)

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Editorial

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Editorial
Editorial—Physical Modelling in Hydraulics Engineering
Water 2021, 13(17), 2317; https://doi.org/10.3390/w13172317 - 24 Aug 2021
Viewed by 491
Abstract
Laboratory experiments and field works play a crucial role in hydraulic research, development, and design as many hydraulic processes elude analytical formulation or, at least for the time being, are not readily nor accurately reproducible with numerical simulations [...] Full article
(This article belongs to the Special Issue Physical Modelling in Hydraulics Engineering)

Research

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Article
Small-Scale Study of Mooring Line Tension Thresholds Based on Impulsive Load Analysis during Big Floating Structure Operation and Commissioning
Water 2021, 13(8), 1056; https://doi.org/10.3390/w13081056 - 12 Apr 2021
Cited by 1 | Viewed by 526
Abstract
Marine wind energy business competitiveness is strongly related to offshore substructures and their logistics. With the aim of avoiding oil and gas methodologies to reduce installation costs, some designs make use of multi-floater systems linked by cables. Optimization of these systems in search [...] Read more.
Marine wind energy business competitiveness is strongly related to offshore substructures and their logistics. With the aim of avoiding oil and gas methodologies to reduce installation costs, some designs make use of multi-floater systems linked by cables. Optimization of these systems in search of larger operational windows increments the likelihood of snap-load event occurrence. This work describes the analysis of cable load during physical model simulation of a DEMOGRAVI3 installation procedure applying statistical and signal-processing methods. The authors describe a simple methodology to define the maximum load threshold for a given mooring line set-up in order to avoid snap loads. Full article
(This article belongs to the Special Issue Physical Modelling in Hydraulics Engineering)
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Article
Experimental and Numerical Study of the Effects of Geometric Appendance Elements on Energy Dissipation over Stepped Spillway
Water 2021, 13(7), 957; https://doi.org/10.3390/w13070957 - 31 Mar 2021
Cited by 6 | Viewed by 691
Abstract
In the stepped spillway, the steps, by providing an artificial roughening bed, dissipate the flow of energy more than other types of spillways, so the construction costs for stilling basin are reduced. However, what is important in this type of spillway is increasing [...] Read more.
In the stepped spillway, the steps, by providing an artificial roughening bed, dissipate the flow of energy more than other types of spillways, so the construction costs for stilling basin are reduced. However, what is important in this type of spillway is increasing the effectiveness of steps in the rate of energy dissipation. The present study deals with experimental and numerical simulations regarding the influence of geometric appendance elements on the steps and its impact on the energy dissipation performances, flow patterns properties, turbulent kinetic energy, flow resistance and the Darcy roughness. The localization of inception point of air entrainment is also assessed. To this aim, different configurations are taken into account. The computational procedure is validated with experimental results and then used to test the hydraulic behavior of different geometric configurations. The results showed that the appendance elements on the steps increased the turbulent kinetic energy (TKE) values and Darcy–Weisbach friction and the energy dissipation increased significantly. By reducing the height of the elements, energy dissipation and the TKE value increase more significantly. With the appendance elements on step, the air entrainment inception locations a positioning further upstream than the flat step stepped spillway. Full article
(This article belongs to the Special Issue Physical Modelling in Hydraulics Engineering)
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Article
Three-Dimensional Flow of a Vortex Drop Shaft Spillway with an Elliptical Tangential Inlet
Water 2021, 13(4), 504; https://doi.org/10.3390/w13040504 - 15 Feb 2021
Cited by 1 | Viewed by 702
Abstract
Vortex drop shaft (VDS) spillways are eco-friendly hydraulic structures used for safely releasing flood. However, due to the complexity of the three-dimensional rotational flow and the lack of suitable measuring devices, current experimental work cannot interpret the flow behavior reliably inside the VDS [...] Read more.
Vortex drop shaft (VDS) spillways are eco-friendly hydraulic structures used for safely releasing flood. However, due to the complexity of the three-dimensional rotational flow and the lack of suitable measuring devices, current experimental work cannot interpret the flow behavior reliably inside the VDS spillway, consequently experimental and CFD study on a VDS spillway with an elliptical tangential inlet was conducted to further discern the interior three-dimensional flow behavior. Hydraulic characteristics such as wall pressure, swirl angle, annular hydraulic height and Froude number of the tapering section are experimentally obtained and acceptably agreed with the numerical prediction. Results indicated that the relative dimensionless maximum height of the standing wave falls off nearly linearly with the increasing Froude number. Nonlinear regression was established to give an estimation of the minimum air-core rate. The normalized height of the hydraulic jump depends on the flow phenomena of pressure slope. Simulated results sufficiently reveal the three-dimensional velocity field (resultant velocity, axial velocity, tangential velocity and radial velocity) with obvious regional and cross-sectional variations inside the vortex drop shaft. It is found that cross-sectional tangential velocity varies, resembling the near-cavity forced vortex and near-wall free vortex behavior. Analytic calculations for the cross-sectional pressure were developed and correlated well with simulated results. Full article
(This article belongs to the Special Issue Physical Modelling in Hydraulics Engineering)
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Article
Numerical Study of Fluctuating Pressure on Stilling Basin Slab with Sudden Lateral Enlargement and Bottom Drop
Water 2021, 13(2), 238; https://doi.org/10.3390/w13020238 - 19 Jan 2021
Cited by 3 | Viewed by 714
Abstract
A stilling basin with sudden enlargement and bottom drop leads to complicated hydraulic characteristics, especially a fluctuating pressure distribution beneath 3D spatial hydraulic jumps. This paper used the large eddy simulation (LES) model and the TruVOF method based on FLOW-3D software to simulate [...] Read more.
A stilling basin with sudden enlargement and bottom drop leads to complicated hydraulic characteristics, especially a fluctuating pressure distribution beneath 3D spatial hydraulic jumps. This paper used the large eddy simulation (LES) model and the TruVOF method based on FLOW-3D software to simulate the time-average pressure, root mean square (RMS) of fluctuating pressure, maximum and minimum pressure of a stilling basin slab. Compared with physical model results, the simulation results show that the LES model can simulate the fluctuating water flow pressure in a stilling basin reliably. The maximum value of RMS of fluctuating pressure appears in the vicinity of the front of the stilling basin and the extension line of the side wall. Based on the generating mechanism of fluctuating pressure and the Poisson Equation derived from the Navier–Stokes Equation, this paper provides a research method of combining quantitative analysis of influencing factors (fluctuating velocity, velocity gradient, and fluctuating vorticity) and qualitative analysis of the characteristics of fluctuating pressure. The distribution of fluctuating pressure in the swirling zone of the stilling basin and the wall-attached jet zone is mainly affected by the vortex and fluctuating flow velocity, respectively, and the distribution in the impinging zone is caused by fluctuating velocity, velocity gradient and fluctuating vorticity. Full article
(This article belongs to the Special Issue Physical Modelling in Hydraulics Engineering)
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Article
Pressure Fluctuations in the Spatial Hydraulic Jump in Stilling Basins with Different Expansion Ratio
Water 2021, 13(1), 60; https://doi.org/10.3390/w13010060 - 30 Dec 2020
Cited by 3 | Viewed by 659
Abstract
Pressure fluctuations are a key issue in hydraulic engineering. However, despite the large number of studies on the topic, their role in spatial hydraulic jumps is not yet fully understood. The results herein shed light on the formation of eddies and the derived [...] Read more.
Pressure fluctuations are a key issue in hydraulic engineering. However, despite the large number of studies on the topic, their role in spatial hydraulic jumps is not yet fully understood. The results herein shed light on the formation of eddies and the derived pressure fluctuations in stilling basins with different expansion ratios. Laboratory tests are conducted in a horizontal rectangular flume with 0.5 m width and 10 m length. The range of approaching Froude numbers spans from 6.4 to 12.5 and the channel expansion ratios are 0.4, 0.6, 0.8, and 1. The effects of approaching flow conditions and expansion ratios are thoroughly analyzed, focusing on the dimensionless standard deviation of pressure fluctuations and extreme pressure fluctuations. The results reveal that these variables show a clear dependence on the Froude number and the distance to the hydraulic jump toe. The maximum values of extreme pressure fluctuations occur in the range 0.609<X<3.385, where X is dimensionless distance from the toe of the hydraulic jump, which makes it highly advisable to reinforce the bed of stilling basins within this range. Full article
(This article belongs to the Special Issue Physical Modelling in Hydraulics Engineering)
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Article
An Augmented Reality Facility to Run Hybrid Physical-Numerical Flood Models
Water 2020, 12(11), 3290; https://doi.org/10.3390/w12113290 - 23 Nov 2020
Cited by 1 | Viewed by 1034
Abstract
This article presents a novel installation for the development of hybrid physical-numerical flood models in an augmented reality environment. This installation extends the concept introduced by the well-known Augmented Reality-SandBox (AR-Sandbox) module, which presents a more educational, and less research-based and professional application. [...] Read more.
This article presents a novel installation for the development of hybrid physical-numerical flood models in an augmented reality environment. This installation extends the concept introduced by the well-known Augmented Reality-SandBox (AR-Sandbox) module, which presents a more educational, and less research-based and professional application. It consists of a physical scale topography built in a sandbox into which other elements (such as buildings, roads or dikes) can be incorporated. A scanner generates, in real time, a Digital Terrain Model (DTM) from the sandbox topography, which serves as a basis for the simulation of overland flow using professional hydraulic software (Iber+). The hydraulic and hydrological parameters (surface roughness, inlet discharges, boundary conditions) are entered with a simple Graphical User Interface (GUI) developed specifically for this project, as indeed was the entire system that allows the visualization of the simulation results. This allows us to obtain quantitative results of flood extension and magnitude, which are represented directly over the physical topography, yielding a realistic visual effect. This installation is conceived for both educational and professional uses. An example of its use is presented, through which its accuracy can be appreciated, and which also illustrates its potential. Full article
(This article belongs to the Special Issue Physical Modelling in Hydraulics Engineering)
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Article
Sediment Morphology and the Flow Velocity Field in a Gully Pot: An Experimental Study
Water 2020, 12(10), 2937; https://doi.org/10.3390/w12102937 - 21 Oct 2020
Cited by 1 | Viewed by 777
Abstract
Urban runoff (re)mobilises solids present on the street surface and transport them to urban drainage systems. The solids reduce the hydraulic capacity of the drainage system due to sedimentation and on the quality of receiving water bodies due to discharges via outfalls and [...] Read more.
Urban runoff (re)mobilises solids present on the street surface and transport them to urban drainage systems. The solids reduce the hydraulic capacity of the drainage system due to sedimentation and on the quality of receiving water bodies due to discharges via outfalls and combined sewer overflows (CSOs) of solids and associated pollutants. To reduce these impacts, gully pots, the entry points of the drainage system, are typically equipped with a sand trap, which acts as a small settling tank to remove suspended solids. This study presents data obtained using Particle Image Velocimetry (PIV) and Laser Doppler Anemometry (LDA) measurements in a scale 1:1 gully to quantify the relation between parameters such as the gully pot geometry, discharge, sand trap depth, and sediment bed level on the flow field and subsequently the settling and erosion processes. The results show that the dynamics of the morphology of the sediment bed influences the flow pattern and the removal efficiency in a significant manner, prohibiting the conceptualization of a gully pot as a completely mixed reactor. Resuspension is initiated by the combination of both high turbulent fluctuations and high mean flow, which is present when a substantial bed level is present. In case of low bed levels, the overlaying water protects the sediment bed from erosion. Full article
(This article belongs to the Special Issue Physical Modelling in Hydraulics Engineering)
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Article
Velocimetry Based on Self-Generated Surface Wave Patterns
Water 2020, 12(9), 2342; https://doi.org/10.3390/w12092342 - 20 Aug 2020
Cited by 1 | Viewed by 671
Abstract
This paper introduces an image analysis technique applied to an artificially-created disturbance at the free surface of a moving water body as a means of quantifying the average velocity of the water stream for shallow flows. The disturbance was created by a thin [...] Read more.
This paper introduces an image analysis technique applied to an artificially-created disturbance at the free surface of a moving water body as a means of quantifying the average velocity of the water stream for shallow flows. The disturbance was created by a thin object penetrating the free surface with different submerged distances. A V-shaped wake pattern was created by the object of interest through its variation with the water body velocity, the submergence and shape of the piercing body. The angle of the wake pattern decreased with the increase of the velocity for a depth-based Froude number ranging from 0.15 to 0.96. The proof-of-concept experiments presented in this paper, therefore, are usable to quantify the velocity based on the wake angle only in subcritical flow conditions. The results showed the shape of the wake was only slightly influenced by the shape of the object geometry and its submergence. Observations on various types of surface wakes have been documented before, but it is the conversion of these observations into a relatively inexpensive and robust method to estimate the velocity of the moving body that is deemed innovative. Full article
(This article belongs to the Special Issue Physical Modelling in Hydraulics Engineering)
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Article
Experimental Characterization of Air Entrainment in Rectangular Free Falling Jets
Water 2020, 12(6), 1773; https://doi.org/10.3390/w12061773 - 22 Jun 2020
Cited by 3 | Viewed by 893
Abstract
This experimental study presents an analysis of the air–water flow in rectangular free-falling jets. The measurements were obtained downstream of a 1.05 m wide sharp-crested weir. The properties of the air–water flow were registered in several cross-sections of the nappe. A conductivity phase [...] Read more.
This experimental study presents an analysis of the air–water flow in rectangular free-falling jets. The measurements were obtained downstream of a 1.05 m wide sharp-crested weir. The properties of the air–water flow were registered in several cross-sections of the nappe. A conductivity phase detection probe was employed, sampling at 20 kHz. Three different specific flows were considered, with energy head over the crest of 0.080, 0.109 and 0.131 m to avoid scale effects. To analyze the flow properties, air–water parameters during the fall, such as the phase change spatial distribution, air–water phase change of frequency, Sauter mean diameter, bubble chord length, turbulent intensities and spectral analyses, were studied. The jet thickness behaviors (inner jet core and free surface) were also analyzed in the falling jet. The jet thickness related to a void fraction of 90% seems to be similar to the theoretical proposal obtained by Castillo et al. (2015), while the jet thickness related to a void fraction of 10% seems to be similar to the jet thickness due to gravitational effects. The results show relative differences in the behavior of the upper and lower sides of the nappe. The experimental data allow us to improve on and complement previous research. Full article
(This article belongs to the Special Issue Physical Modelling in Hydraulics Engineering)
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Article
Experimental Characterization of the Hydraulic Jump Profile and Velocity Distribution in a Stilling Basin Physical Model
Water 2020, 12(6), 1758; https://doi.org/10.3390/w12061758 - 20 Jun 2020
Cited by 4 | Viewed by 1013
Abstract
The study of the hydraulic jump developed in stilling basins is complex to a high degree due to the intense velocity and pressure fluctuations and the significant air entrainment. It is this complexity, bound to the practical interest in stilling basins for energy [...] Read more.
The study of the hydraulic jump developed in stilling basins is complex to a high degree due to the intense velocity and pressure fluctuations and the significant air entrainment. It is this complexity, bound to the practical interest in stilling basins for energy dissipation purposes, which brings the importance of physical modeling into the spotlight. However, despite the importance of stilling basins in engineering, bibliographic studies have traditionally focused on the classical hydraulic jump. Therefore, the objective of this research was to study the characteristics of the hydraulic jump in a typified USBR II stilling basin, through a physical model. The free surface profile and the velocity distribution of the hydraulic jump developed within this structure were analyzed in the model. To this end, an experimental campaign was carried out, assessing the performance of both, innovative techniques such as the time-of-flight camera and traditional instrumentation like the Pitot tube. The results showed a satisfactory representation of the free surface profile and the velocity distribution, despite some discussed limitations. Furthermore, the instrumentation employed revealed the important influence of the energy dissipation devices on the flow properties. In particular, relevant differences were found for the hydraulic jump shape and the maximum velocity positions within the measured vertical profiles, when compared to classical hydraulic jumps. Full article
(This article belongs to the Special Issue Physical Modelling in Hydraulics Engineering)
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Article
Prediction of Mean Wave Overtopping Discharge Using Gradient Boosting Decision Trees
Water 2020, 12(6), 1703; https://doi.org/10.3390/w12061703 - 15 Jun 2020
Cited by 8 | Viewed by 1024
Abstract
Wave overtopping is an important design criterion for coastal structures such as dikes, breakwaters and promenades. Hence, the prediction of the expected wave overtopping discharge is an important research topic. Existing prediction tools consist of empirical overtopping formulae, machine learning techniques like neural [...] Read more.
Wave overtopping is an important design criterion for coastal structures such as dikes, breakwaters and promenades. Hence, the prediction of the expected wave overtopping discharge is an important research topic. Existing prediction tools consist of empirical overtopping formulae, machine learning techniques like neural networks, and numerical models. In this paper, an innovative machine learning method—gradient boosting decision trees—is applied to the prediction of mean wave overtopping discharges. This new machine learning model is trained using the CLASH wave overtopping database. Optimizations to its performance are realized by using feature engineering and hyperparameter tuning. The model is shown to outperform an existing neural network model by reducing the error on the prediction of the CLASH database by a factor of 2.8. The model predictions follow physically realistic trends for variations of important features, and behave regularly in regions of the input parameter space with little or no data coverage. Full article
(This article belongs to the Special Issue Physical Modelling in Hydraulics Engineering)
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Article
Zonation of Positively Buoyant Jets Interacting with the Water-Free Surface Quantified by Physical and Numerical Modelling
Water 2020, 12(5), 1324; https://doi.org/10.3390/w12051324 - 07 May 2020
Cited by 1 | Viewed by 1063
Abstract
The evolution of positively buoyant jets was studied with non-intrusive techniques—Particle Image Velocimetry (PIV) and Laser Induce Fluorescence (LIF)—by analyzing four physical tests in their four characteristic zones: momentum dominant zone (jet-like), momentum to buoyancy transition zone (jet to plume), buoyancy dominant zone [...] Read more.
The evolution of positively buoyant jets was studied with non-intrusive techniques—Particle Image Velocimetry (PIV) and Laser Induce Fluorescence (LIF)—by analyzing four physical tests in their four characteristic zones: momentum dominant zone (jet-like), momentum to buoyancy transition zone (jet to plume), buoyancy dominant zone (plume-like), and lateral dispersion dominant zone. Four configurations were tested modifying the momentum and the buoyancy of the effluent through variations of flow discharge and the thermal gradient with the receiving water body, respectively. The physical model results were used to evaluate the performance of numerical models to describe such flows. Furthermore, a new method to delimitate the four characteristic zones of positively buoyant jets interacting with the water-free surface was proposed using the angle (α) shaped by the tangent of the centerline trajectory and the longitudinal axis. Physical model results showed that the dispersion of mass (concentrations) was always greater than the dispersion of energy (velocity) during the evolution of positively buoyant jets. The semiempirical models (CORJET and VISJET) underestimated the trajectory and overestimated the dilution of positively buoyant jets close to the impact zone with the water-free surface. The computational fluid dynamics (CFD) model (Open Field Operation And Manipulation model (OpenFOAM)) is able to reproduce the behavior of positively buoyant jets for all the proposed zones according to the physical results. Full article
(This article belongs to the Special Issue Physical Modelling in Hydraulics Engineering)
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Article
Study on Flow Velocity during Wheeled Capsule Hydraulic Transportation in a Horizontal Pipe
Water 2020, 12(4), 1181; https://doi.org/10.3390/w12041181 - 20 Apr 2020
Cited by 1 | Viewed by 804
Abstract
As a clean, low-carbon, and green hydraulic transportation technology, wheeled capsule pipeline hydraulic transportation is a transportation mode conducive to the sustainable development of the social economy. Based on the method of a physical model experiment and hydraulic theory, the flow velocity characteristics [...] Read more.
As a clean, low-carbon, and green hydraulic transportation technology, wheeled capsule pipeline hydraulic transportation is a transportation mode conducive to the sustainable development of the social economy. Based on the method of a physical model experiment and hydraulic theory, the flow velocity characteristics in the pipeline when the wheeled capsule with a length–diameter ratio of 2.5 and 2.14, respectively, was transported in the straight pipe section with an inner diameter of 100 mm were studied in this paper. The results show that in the process of transporting materials, the flow velocity distribution of the cross section near the upstream and downstream section of the capsule was basically the same, and the axial velocity was smaller in the middle of the pipe and larger near the inner wall of the pipe. The radial velocity distribution was more thinly spread near the pipe wall and denser near the center of the pipe. The circumferential flow velocity was distributed in the vicinity of the support body of the wheeled capsule. For any annular gap section around the wheeled capsule, the radial velocity of annular gap flow was very small, and the average radial velocity of annular gap flow was about 1/30 of the average axial velocity of annular gap flow and about 0.7 of the average circumferential velocity of annular gap flow. The axial, circumferential, and radial flow velocities on the same radius measuring ring changed with the polar axis in a wave pattern of alternating peaks and troughs. These results can provide the theoretical basis for optimizing structural parameters of the wheeled capsule. Full article
(This article belongs to the Special Issue Physical Modelling in Hydraulics Engineering)
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Article
Variation of Coefficient of Friction and Friction Head Losses Along a Pipe with Multiple Outlets
Water 2020, 12(3), 844; https://doi.org/10.3390/w12030844 - 17 Mar 2020
Cited by 3 | Viewed by 1006
Abstract
The flow in a pipe having multiple outlets is considered as an advanced problem in hydraulic engineering; many discrepancies were found in the literature, in addition to the lack of experimental and field studies. The main goal of this study is to simulate [...] Read more.
The flow in a pipe having multiple outlets is considered as an advanced problem in hydraulic engineering; many discrepancies were found in the literature, in addition to the lack of experimental and field studies. The main goal of this study is to simulate the flow in a pipe with multiple outlets in order to examine the existing methodologies for estimation of the friction head losses, and to propose a methodology that is based on experimental data. The main physical model in this study consisted of a water supply tank, a pipe with multiple outlets having a piezometer at each outlet. Different pipe diameters were used in this study, the pipe diameters were 25.4 mm (1 in), 38.1 mm (1.5 in), 50.8 (2 in) and 76.2 mm (3 in). The inlet heads used were 1.7 m and 2.2 m. The data collected from different flow conditions were used to assess the variation in the coefficient of friction and friction head losses along the pipe length. It can be concluded that the spacing between any two successive outlets (S) and area ratio (AR = Area of outlet/Area of the main pipe) are the main factors affecting the friction head losses along the pipe. The ratio of total friction head losses along a pipe with outlets having the same properties (length (L), discharge (Q), diameter (d) and material) to a pipe without outlets and having the same properties is called the G factor. The G factor calculated using selected formulae was overestimated in comparison to the calculated G factor obtained from experimental data. For large values of S/d (spacing between outlets/diameter of main pipe), the difference between coefficient of friction in first segment (f1) and last segment (fn) of the multiple outlet pipe was noted to be minimal. Full article
(This article belongs to the Special Issue Physical Modelling in Hydraulics Engineering)
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Article
Oblique Wave Attack on Rubble Mound Breakwater Crest Walls of Finite Length
Water 2020, 12(2), 353; https://doi.org/10.3390/w12020353 - 28 Jan 2020
Cited by 8 | Viewed by 1441
Abstract
Rubble mound breakwaters usually present a crest wall to increase the crest freeboards without a large increase of the consumption of material. Methods in the literature to design crest walls are based on estimates of the wave loads. These methods are focused on [...] Read more.
Rubble mound breakwaters usually present a crest wall to increase the crest freeboards without a large increase of the consumption of material. Methods in the literature to design crest walls are based on estimates of the wave loads. These methods are focused on the maximum loading that attacks a single position of the crest wall. In practice, crest walls have a finite length. Since the maximum loading does not occur at the same instant over the entire length of the crest wall for oblique waves, these methods overestimate the loading in the situation of oblique waves. Wave loads under oblique wave attack have been measured in physical model tests. A method to account for the effect of the finite length of crest walls has been developed, and design guidelines have been derived. The results of this study in combination with the existing methods in the literature to estimate the wave forces enable a more advanced design of crest walls. Full article
(This article belongs to the Special Issue Physical Modelling in Hydraulics Engineering)
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Article
SewerSedFoam: A Model for Free Surface Flow, Sediment Transport, and Deposited Bed Morphology in Sewers
Water 2020, 12(1), 270; https://doi.org/10.3390/w12010270 - 17 Jan 2020
Cited by 2 | Viewed by 1646
Abstract
This paper aims to bridge the gap in the detailed modelling of flow and sediment process interactions in sewers through the development of a computational fluid dynamics (CFD) model. It draws on previous models developed for surface water sediment transport in the OpenFOAM [...] Read more.
This paper aims to bridge the gap in the detailed modelling of flow and sediment process interactions in sewers through the development of a computational fluid dynamics (CFD) model. It draws on previous models developed for surface water sediment transport in the OpenFOAM CFD framework and builds on them to improve their suitability for sewer sediment processes. Three distinct sediment processes, suspended sediment transport, bedload transport, and deposited bed morphology, are incorporated into a free surface flow solver, interFoam. This sewer sediment model, called SewerSedFoam, models the impacts of sediment deposition and erosion on flow velocity by using dynamic mesh deformation to capture the movement of the deposited bed and its morphology. Further, three sediment classes, two suspended and one bedload sediment, can be modelled along with some bed stabilization and consolidation effects during deposition and erosion, respectively. The functionality of the overall model in modelling sewer sediment deposition and erosion is promising, although the validation of a large magnitude sediment erosion event has been limited by the availability of granular data in existing case studies. Full article
(This article belongs to the Special Issue Physical Modelling in Hydraulics Engineering)
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Article
The Wall Stress of the Capsule Surface in the Straight Pipe
Water 2020, 12(1), 242; https://doi.org/10.3390/w12010242 - 15 Jan 2020
Cited by 3 | Viewed by 1024
Abstract
Hydraulic capsule transportation is a new energy-saving transport mode. It is of great significance to the study of flow-field characteristics and pipeline-stress analysis. The purpose of this paper was to analyze the stress distribution on capsule surfaces when there is stationary in pipe [...] Read more.
Hydraulic capsule transportation is a new energy-saving transport mode. It is of great significance to the study of flow-field characteristics and pipeline-stress analysis. The purpose of this paper was to analyze the stress distribution on capsule surfaces when there is stationary in pipe flow. Results showed that the maximum shear stress on the capsule wall appeared in the rear section. Shear-stress range was between 0 and 38 Pa. Principal stress exerted great force on the capsule. The circumferential component of the principal stress was the largest, followed by the axial component, and the radial component was the smallest, i.e., σc > σa> σr. The larger the discharge of pipe flow, the greater the influence of unit discharge on wall shear stress and capsule principal stress, that is, k1 < k2< k3. Under the conditions of this experiment, the axial component of principal stress should include shear stress on the capsule, and Reynolds stress on the capsule cannot be neglected due to water-flow turbulence. Full article
(This article belongs to the Special Issue Physical Modelling in Hydraulics Engineering)
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Article
Development and Calibration of a New Dripper-Based Rainfall Simulator for Large-Scale Sediment Wash-Off Studies
Water 2020, 12(1), 152; https://doi.org/10.3390/w12010152 - 04 Jan 2020
Cited by 3 | Viewed by 1187
Abstract
Rainfall simulators are useful tools for controlling the main variables that govern natural rainfall. In this study, a new drop-forming rainfall simulator, which consists of pressure-compensating dripper grids above a horizontal mesh that breaks and distributes raindrops, was developed to be applied in [...] Read more.
Rainfall simulators are useful tools for controlling the main variables that govern natural rainfall. In this study, a new drop-forming rainfall simulator, which consists of pressure-compensating dripper grids above a horizontal mesh that breaks and distributes raindrops, was developed to be applied in wash-off experiments in a large-scale physical model of 36 m2. The mesh typology and size, and its distance to drippers, were established through a calibration where rain uniformity and distributions of raindrop sizes and velocities were compared with local natural rainfall. Finally, the rain properties of the final solution were measured for the three rain intensities that the rainfall simulator is able to generate (30, 50 and 80 mm/h), obtaining almost uniform rainfalls with uniformity coefficients of 81%, 89% and 91%, respectively. This, together with the very suitable raindrop size distribution obtained, and the raindrop velocities of around 87.5% of the terminal velocity for the mean raindrop diameter, makes the proposed solution optimal for wash-off studies, where rain properties are key in the detachment of particles. In addition, the flexibility seen in controlling rain characteristics increases the value of the proposed design in that it is adaptable to a wide range of studies. Full article
(This article belongs to the Special Issue Physical Modelling in Hydraulics Engineering)
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Article
The Use of a Microscale Physical Model to Simulate Bankfull Discharge in the Lower Reaches of the Yellow River
Water 2020, 12(1), 13; https://doi.org/10.3390/w12010013 - 19 Dec 2019
Cited by 2 | Viewed by 799
Abstract
Microscale physical models (MSPMs) were once widely used in flood planning in large basins. They fell out of favor but are now being used again. This paper explores the benefits of using such a model for understanding a flood problem on the Lower [...] Read more.
Microscale physical models (MSPMs) were once widely used in flood planning in large basins. They fell out of favor but are now being used again. This paper explores the benefits of using such a model for understanding a flood problem on the Lower Yellow River (LYR). We constructed an indoor MSPM of a nearly 800-km reach of the LYR. The model had different scales in the longitudinal, transverse, and vertical directions, and we adjusted the slope of the model. Meanwhile, a real-time water level monitoring system and an automatic flow control system were built on the MSPM to automatically control hydrodynamic testing. Through several discharge experiments, bankfull discharge for multiple MSPM sections was obtained and compared with measured data from the corresponding hydrological section of the prototype during the early flood season of 2016. The comparison demonstrated good linear correlation. The analysis of model similarity showed that although there was some deviation in gravity similarity between the MSPM and the prototype, the model discharge scale derived from resistance similarity adequately described the relationship between the model and the prototype bankfull discharge. Further analysis of the relationship between the model and the prototype bankfull discharge revealed that a split-line line may be better than a single regression line. A MSPM could reproduce the bankfull discharge of the LYR with the nearly 800-km reach in the laboratory which is impossible for a small distortion rate physical model, and obtain a result close to that of the assimilated numerical model. Full article
(This article belongs to the Special Issue Physical Modelling in Hydraulics Engineering)
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