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Turbulence in River and Maritime Hydraulics
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Turbulence in River and Maritime Hydraulics

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

Deadline for manuscript submissions: closed (28 February 2018) | Viewed by 74368

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Prof. Dr. Michele Mossa

E-Mail Website
Guest Editor
Department of Civil, Environmental, Land, Building Engineering and Chemistry—DICATECh, Polytechnic University of Bari, Via E. Orabona, 4, 70125 Bari, Italy
Interests: hydraulics; fluid mechanics; environmental hydraulics; maritime hydraulics; rivers and stream; contaminant transport; physical models in hydraulics; tidal mixing; wastewater disposal; stratification
Dr. Donatella Termini

E-Mail Website
Guest Editor
Department of Engineering, University of Palermo, Palermo, Italy
Interests: present research efforts include the investigation in fluvial hydraulics and eco-hydraulics (flow resistance, effect of vegetation, sediment transport, effects of bed roughness), prediction of river morphological evolution (meandering and braiding) both through experimental investigations and by the development of numerical simulation codes
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Peter A. Davies

E-Mail Website
Guest Editor
Department of Civil Engineering, University of Dundee, UK
Interests: internal waves, wastewater disposal, ocean circulation

Special Issue Information

Dear Colleagues,

You are kindly invited to submit a manuscript on any aspect of theoretical analysis and/or experimental results on river and maritime hydraulics, highlighting the most recent breakthrough(s) in the processes of contaminant and particle transport and mixing processes.

The papers will be published in a Special Issue of Water, with the main aim being to present the state-of-the-art knowledge of complex environmental flows to researchers and practitioners.

The content of the paper is at your discretion, but an overview of a particular topic of research in your area of expertise and an exposure of the current and future challenges associated with this topic would be particularly valuable.

Prof. Dr. Michele Mossa
Prof. Dr. Donatella Termini
Prof. Dr. Peter A. Davies
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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 2600 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

  • environmental hydraulics

  • contaminant transport, particle transport and mixing process

  • stratified flows

  • turbulence

Published Papers (16 papers)

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Editorial

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3 pages, 150 KiB  
Editorial
Turbulence in River and Maritime Hydraulics
by Michele Mossa, Donatella Termini and Peter Davies
Water 2018, 10(7), 963; https://doi.org/10.3390/w10070963 - 23 Jul 2018
Cited by 1 | Viewed by 3399
Abstract
Understanding of the role of turbulence in controlling transport processes is of paramount importance for the preservation and protection of aquatic ecosystems, the minimisation of deleterious consequences of anthropogenic activity, and the successful sustainable development of river and maritime areas. In this context, [...] Read more.
Understanding of the role of turbulence in controlling transport processes is of paramount importance for the preservation and protection of aquatic ecosystems, the minimisation of deleterious consequences of anthropogenic activity, and the successful sustainable development of river and maritime areas. In this context, the present Special Issue collects 15 papers which provide a representation of the present understanding of turbulent processes and their effects in river and maritime environments. The presented collection of papers is not exhaustive but it allows for highlighting key priority areas and knowledge gaps in this field of research. Full article
(This article belongs to the Special Issue Turbulence in River and Maritime Hydraulics)

Research

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18 pages, 4995 KiB  
Article
On the Effect of Regular Waves on Inclined Negatively Buoyant Jets
by Simone Ferrari, Maria Grazia Badas and Giorgio Querzoli
Water 2018, 10(6), 726; https://doi.org/10.3390/w10060726 - 03 Jun 2018
Cited by 10 | Viewed by 3782
Abstract
The target of this paper is to measure the modifications that regular waves induce on the geometrical features and dilution of inclined negatively buoyant jets. In order to achieve this aim, we have carried out a set of experiments in a wavemaker-equipped flume, [...] Read more.
The target of this paper is to measure the modifications that regular waves induce on the geometrical features and dilution of inclined negatively buoyant jets. In order to achieve this aim, we have carried out a set of experiments in a wavemaker-equipped flume, by measuring the concentration fields via light-induced fluorescence, a non-intrusive and full-field image analysis technique. The wave and jet parameters were selected in order to simulate the case of a typical discharge of brine, from a desalination plant, into the Mediterranean Sea, and compare it to a reference case, i.e., the same jet discharging into a stagnant water body. The mean concentration fields were obtained, as well as the geometrical features and dilution of the jets. The three main effects of waves on inclined negatively buoyant jets are the bifurcation (i.e., the separation in two branches), the rotation of the point of maximum height and the oscillation of the impact point around a fixed position different from the stationary one, and the reduction in size of the sea region interested by the discharge; this last effect increases with the wave period. As a consequence, under waves with high period and amplitude, the dilution of inclined negatively buoyant jets tends to decrease. Full article
(This article belongs to the Special Issue Turbulence in River and Maritime Hydraulics)
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18 pages, 2086 KiB  
Article
Computational Fluid Dynamics for Modeling Gravity Currents in the Presence of Oscillatory Ambient Flow
by Laura Maria Stancanelli, Rosaria Ester Musumeci and Enrico Foti
Water 2018, 10(5), 635; https://doi.org/10.3390/w10050635 - 14 May 2018
Cited by 9 | Viewed by 4450
Abstract
Gravity currents generated by lock release are studied in the case of initially quiescent ambient fluid and oscillating ambient fluid (regular surface waves). In particular, the dynamics of the density currents are investigated by means of CFD numerical simulations. The aim is to [...] Read more.
Gravity currents generated by lock release are studied in the case of initially quiescent ambient fluid and oscillating ambient fluid (regular surface waves). In particular, the dynamics of the density currents are investigated by means of CFD numerical simulations. The aim is to evaluate the influence of the ambient fluid velocity field on the observed mixing and turbulent processes. Results of two different turbulence closure models, namely the standard k − ε turbulence model and the LES model, are analyzed. Model predictions are validated through comparison with laboratory measurements. Results show that the k − ε model is able to catch the main current propagation parameters (e.g., front velocity at the different phases of the evolution of the current, gravity current depth, etc.), but that a LES model provides more realistic insights into the turbulent processes (e.g., formation of interfacial Kelvin–Helmholtz billows, vortex stretching and eventual break up into 3D turbulence). The ambient fluid velocity field strongly influences the dynamics of the gravity currents. In particular, the presence of an oscillatory motion induces a relative increase of mixing at the front (up to 25%) in proximity of the bottom layer, and further upstream, an increase of the mixing process (up to 60%) is observed due to the mass transport generated by waves. The observed mixing phenomena observed are also affected by the ratio between the gravity current velocity v f and the horizontal orbital velocity induced by waves u w , which has a stronger impact in the wave dominated regime ( v f / u w < 1). Full article
(This article belongs to the Special Issue Turbulence in River and Maritime Hydraulics)
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16 pages, 4825 KiB  
Article
Influence of Gravel-Bed Porosity and Grain Orientation on Bulk Flow Resistance
by Christy Ushanth Navaratnam, Jochen Aberle, Jie Qin and Pierre-Yves Henry
Water 2018, 10(5), 561; https://doi.org/10.3390/w10050561 - 26 Apr 2018
Cited by 7 | Viewed by 5028
Abstract
This paper presents results from experiments that were carried out to study the effect of porosity and grain orientation on flow resistance. Experiments were performed over three rough surfaces; a water-worked gravel-bed, its non-porous facsimile (cast-bed) and the rotated cast-bed (cast tiles rotated [...] Read more.
This paper presents results from experiments that were carried out to study the effect of porosity and grain orientation on flow resistance. Experiments were performed over three rough surfaces; a water-worked gravel-bed, its non-porous facsimile (cast-bed) and the rotated cast-bed (cast tiles rotated through 180°). The first two beds were used to isolate the influence of gravel-bed porosity on the bulk flow resistance and the rotated cast was used to study effect of the grain orientation on the flow resistance. The results showed that the rotated cast-bed exerted the highest flow resistance whereas the porous water-worked gravel-bed was, for comparable hydraulic boundary conditions, characterized by slightly higher flow resistance than its non-porous counterpart. The results from the bulk flow analysis were substantiated by a preliminary analysis of flow velocity data. Full article
(This article belongs to the Special Issue Turbulence in River and Maritime Hydraulics)
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29 pages, 32268 KiB  
Article
Waves and Currents at a River Mouth: The Role of Macrovortices, Sub-Grid Turbulence and Seabed Friction
by Lorenzo Melito, Matteo Postacchini, Giovanna Darvini and Maurizio Brocchini
Water 2018, 10(5), 550; https://doi.org/10.3390/w10050550 - 25 Apr 2018
Cited by 7 | Viewed by 5127
Abstract
Numerical experiments of wave-current interaction have been performed to investigate the evolution and dissipation of horizontal large-scale vortical structures generated by differential wave breaking and current shearing at river mouths. Specific focus is on the role played by turbulence of scales smaller than [...] Read more.
Numerical experiments of wave-current interaction have been performed to investigate the evolution and dissipation of horizontal large-scale vortical structures generated by differential wave breaking and current shearing at river mouths. Specific focus is on the role played by turbulence of scales smaller than the water depth and by seabed friction on the dissipation of the mentioned macrovortices. The analysis reveals two regions of turbulence generation: at the river mouth, and along the curved seaward boundary of the shoal. In the latter zone, macrovortices are formed due to differential wave breaking induced by the sudden variation in water depth and enhanced by opposing currents which favour wave steepening. Such vortices are then advected towards the shore. Among the dissipative mechanisms, dissipation induced by seabed friction is deemed dominant, in particular in the most shallow waters of the shoal. Sub-grid turbulence dissipation, conversely, is more efficient offshore, although exerting some effect also over the shoal when supported by the continuous action of waves. Full article
(This article belongs to the Special Issue Turbulence in River and Maritime Hydraulics)
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20 pages, 6898 KiB  
Article
Some Aspects of Turbulent Mixing of Jets in the Marine Environment
by Michele Mossa and Peter A. Davies
Water 2018, 10(4), 522; https://doi.org/10.3390/w10040522 - 21 Apr 2018
Cited by 15 | Viewed by 5911
Abstract
Prominent among environmental problems is the pollution of the coastal marine zone as a result of anthropogenic activities. On this point, while studies of jets in still water and in crossflows have been developed in many research centres, studies on jets interacting with [...] Read more.
Prominent among environmental problems is the pollution of the coastal marine zone as a result of anthropogenic activities. On this point, while studies of jets in still water and in crossflows have been developed in many research centres, studies on jets interacting with waves are still rare. The present study analyses turbulent, non-buoyant water jets issued into a wave environment. A comparison of the time-averaged and phase-averaged velocity components has been carried out, in order to highlight the flow patterns in the two configurations. The experimental data have also been compared with others in the literature, such as the relationship between the dimensionless, longitudinal, time-averaged velocities of the jet mean axis and the distance from the source. Such comparisons reveal a good agreement. Furthermore, using the analogy between the equation of the turbulent transport of a solute concentration and the equation of the turbulent kinetic energy, the paper presents also estimates of the turbulence diffusion coefficients and advection terms of jets in a wave environment. The experimental results are compared with jets in still water. With the presence of waves, the turbulence length-scales in the streamwise direction vary, contributing to an increase in streamwise turbulent diffusion, relative to the condition of the same jet in still water. The analysis of the jet streamwise advection term reveals that it increases in the case of jets in a wave environment, as compared to no-wave conditions. Full article
(This article belongs to the Special Issue Turbulence in River and Maritime Hydraulics)
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23 pages, 24999 KiB  
Article
Effect of the Junction Angle on Turbulent Flow at a Hydraulic Confluence
by Nadia Penna, Mauro De Marchis, Olga B. Canelas, Enrico Napoli, António H. Cardoso and Roberto Gaudio
Water 2018, 10(4), 469; https://doi.org/10.3390/w10040469 - 12 Apr 2018
Cited by 31 | Viewed by 5969
Abstract
Despite the existing knowledge concerning the hydrodynamic processes at river junctions, there is still a lack of information regarding the particular case of low width and discharge ratios, which are the typical conditions of mountain river confluences. Aiming at filling this gap, laboratory [...] Read more.
Despite the existing knowledge concerning the hydrodynamic processes at river junctions, there is still a lack of information regarding the particular case of low width and discharge ratios, which are the typical conditions of mountain river confluences. Aiming at filling this gap, laboratory and numerical experiments were conducted, comparing the results with literature findings. Ten different confluences from 45 ∘ to 90 ∘ were simulated to study the effects of the junction angle on the flow structure, using a numerical code that solves the 3D Reynolds Averaged Navier-Stokes (RANS) equations with the k- ϵ turbulence closure model. The results showed that the higher the junction angle, the wider and longer the retardation zone at the upstream junction corner and the separation zone, and the greater the flow deflection at the entrance of the tributary into the post-confluence channel. Furthermore, it was shown that the maximum streamwise velocity does not necessarily increase with the junction angle and that it is not always located in the contraction section. Full article
(This article belongs to the Special Issue Turbulence in River and Maritime Hydraulics)
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16 pages, 23816 KiB  
Article
Flow Characteristics in the Wake Region of a Finite-Length Vegetation Patch in a Partly Vegetated Channel
by Didem Yılmazer, Ayşe Yüksel Ozan and Kubilay Cihan
Water 2018, 10(4), 459; https://doi.org/10.3390/w10040459 - 11 Apr 2018
Cited by 12 | Viewed by 4017
Abstract
Aquatic vegetation in rivers and coastal regions controls the flow structure in terms of mean velocity and turbulence. The vegetation in the flow affects the transportation of nutrients, microbes, dissolved oxygen, sediment, and contaminants; therefore, the flow characteristics of different types of vegetation [...] Read more.
Aquatic vegetation in rivers and coastal regions controls the flow structure in terms of mean velocity and turbulence. The vegetation in the flow affects the transportation of nutrients, microbes, dissolved oxygen, sediment, and contaminants; therefore, the flow characteristics of different types of vegetation layers should be examined in order to understand the effects of vegetation on the flow structure. In this paper, the effect of the submergence ratio and SVF (Solid Volume of Fraction) of a vegetation patch, which was present across half of the channel in a spanwise direction, on the flow structure at the wake region was examined. For this purpose, different submergence ratios with different SVFs were considered in the experiments, and velocity measurements were performed in the wake region of the vegetation layer with an Acoustic Doppler Velocimeter (ADV). According to the results, the effect of different vegetation heights and SVFs on the velocity distribution was obtained. Moreover, inflectional velocity distribution over the cross-section in the wake region of the vegetation layer was obtained, and it was concluded that jet flow occurred in the non-vegetated half of the channel due to the vegetation layer. Full article
(This article belongs to the Special Issue Turbulence in River and Maritime Hydraulics)
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13 pages, 18922 KiB  
Article
Wave Height Attenuation and Flow Resistance Due to Emergent or Near-Emergent Vegetation
by Paolo Peruzzo, Francesca De Serio, Andrea Defina and Michele Mossa
Water 2018, 10(4), 402; https://doi.org/10.3390/w10040402 - 29 Mar 2018
Cited by 29 | Viewed by 6616
Abstract
Vegetation plays a pivotal role in fluvial and coastal flows, affecting their structure and turbulence, thus having a strong impact on the processes of transport and diffusion of nutrients and sediments, as well as on ecosystems and habitats. In the present experimental study, [...] Read more.
Vegetation plays a pivotal role in fluvial and coastal flows, affecting their structure and turbulence, thus having a strong impact on the processes of transport and diffusion of nutrients and sediments, as well as on ecosystems and habitats. In the present experimental study, the attenuation of regular waves propagating in a channel through flexible vegetation is investigated. Specifically, artificial plants mimicking Spartina maritima are considered. Different plant densities and arrangements are tested, as well as different submergence ratios. Measurements of wave characteristics by six wave gauges, distributed all along the vegetated stretch, allow us to estimate the wave energy dissipation. The flow resistance opposed by vegetation is inferred by considering that drag and dissipation coefficients are strictly related. The submergence ratio and the stem density, rather than the wave characteristics, affect the drag coefficient the most. A comparison with the results obtained in the case when the same vegetation is placed in a uniform flow is also shown. It confirms that the drag coefficient for the canopy is lower than for an isolated cylinder, even if the reduction is not affected by the stem density, underlining that flow unsteadiness might be crucial in the process of dissipation. Full article
(This article belongs to the Special Issue Turbulence in River and Maritime Hydraulics)
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17 pages, 12130 KiB  
Article
Wave–Current Interaction: A 2DH Model for Turbulent Jet and Bottom-Friction Dissipation
by Sara Pascolo, Marco Petti and Silvia Bosa
Water 2018, 10(4), 392; https://doi.org/10.3390/w10040392 - 27 Mar 2018
Cited by 19 | Viewed by 4206
Abstract
A correct representation of the non-linear interactions between waves and currents is one of the key points when studying the morphological evolution of nearshore environments, in particular close to river mouths or tidal inlets. Undoubtedly, the numerical modelling of similar phenomena can be [...] Read more.
A correct representation of the non-linear interactions between waves and currents is one of the key points when studying the morphological evolution of nearshore environments, in particular close to river mouths or tidal inlets. Undoubtedly, the numerical modelling of similar phenomena can be very complex and computationally demanding, given the size of the domains. In the present paper, a two‐dimensional horizontal (2DH) numerical model is applied to investigate the hydrodynamics of a turbulent jet current interacting with frontal waves, preparatory to the study of morphodynamical processes. The purpose is to reproduce accurately the turbulence of the current flow, which develops in both vertical and horizontal planes, even with the simplifications of depth-averaged velocities. Moreover, the bottom shear stress induces a mechanism of dissipation, which acts both on the jet hydrodynamics and on the wave field. Significant attention is given to this process, which turns out to be crucial in shallow waters. The present model, based on classic shallow-water equations and wave action balance, is applied to a literature test. Comparisons with theoretical and numerical outcomes are shown, the latter obtained with a quasi-3D model. Full article
(This article belongs to the Special Issue Turbulence in River and Maritime Hydraulics)
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17 pages, 26673 KiB  
Article
Experimental and Numerical Investigation of Pre-Breaking and Breaking Vorticity within a Plunging Breaker
by Diana De Padova, Maurizio Brocchini, Federica Buriani, Sara Corvaro, Francesca De Serio, Michele Mossa and Stefano Sibilla
Water 2018, 10(4), 387; https://doi.org/10.3390/w10040387 - 26 Mar 2018
Cited by 25 | Viewed by 3710
Abstract
The characteristics of vorticity induced just prior and at the splash-down of a plunging breaker on a 1:10 planar slope have been studied using wave flume experiments and numerical simulations. Laboratory experiments involved detailed measurements in the outer surf zone of both fluid [...] Read more.
The characteristics of vorticity induced just prior and at the splash-down of a plunging breaker on a 1:10 planar slope have been studied using wave flume experiments and numerical simulations. Laboratory experiments involved detailed measurements in the outer surf zone of both fluid velocities below trough level, achieved by a fibre-optic laser-Doppler anemometer, and water surface elevations, obtained by an ultrasound probe. A Weakly-Compressible Smoothed Particle (WCSPH) model, coupled with a two-equation model for turbulent stresses, has been employed for the numerical simulations. A thorough calibration of the SPH’s numerical parameters has been first performed, through comparison between numerical and experimental wave elevation and velocity data. Then, considering that time-averaged laboratory data shows a significant vorticity beneath the free surface in the wave pre-breaking region, the vorticity generation mechanism has been thoroughly analyzed by means of the numerical model. In the attempt of explaining the generation of vorticity as induced by flow separation, we also inspected the role of the streamwise flow deceleration and surface-parallel vorticity flux. In analogy with the case of spilling breakers a cause-effect relation has been observed between streamwise flow deceleration and vorticity generation. Numerical findings are positively confirmed by the experimental results. Full article
(This article belongs to the Special Issue Turbulence in River and Maritime Hydraulics)
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19 pages, 41564 KiB  
Article
Advanced 3D Mapping of Hydrodynamic Parameters for the Analysis of Complex Flow Motions in a Submerged Bedrock Canyon of the Tocantins River, Brazil
by Gustavo Tomas, Tobias Bleninger, Colin D. Rennie and Henrique Guarneri
Water 2018, 10(4), 367; https://doi.org/10.3390/w10040367 - 23 Mar 2018
Cited by 6 | Viewed by 4879
Abstract
Validation and scaling of sophisticated physical and numerical fluvial hydraulic models to real field conditions are limited by temporal and spatial constraints of field measurement technologies. These limitations increase when analyzing hydraulic properties of complex river forms such as submerged bedrock canyons. The [...] Read more.
Validation and scaling of sophisticated physical and numerical fluvial hydraulic models to real field conditions are limited by temporal and spatial constraints of field measurement technologies. These limitations increase when analyzing hydraulic properties of complex river forms such as submerged bedrock canyons. The analysis of flow under these conditions has demonstrated non-linear behavior, strong secondary circulation and a high level of turbulence. The objective of this paper is to obtain and analyze turbulence and secondary current information for flow analysis, by evaluating the spatial distribution of bed shear stress and eddy viscosity with acoustic Doppler current profiler (ADCP) measurements. The real field-scale case study was the Lourenço Rock Canyon in Tocantins River, Brazil. A total of 10,531 velocity profiles were measured with an ADCP adapted to a moving boat. The data were post-processed by decomposing the velocity data measurements and calculating the standard deviations. Three different methods are compared for bed shear stress: total kinetic energy (TKE), law of the wall and the depth–slope product. The eddy viscosity was estimated with the Boussinesq approach. The initial data processing confirmed turbulence and flow velocity characteristics described in similar literature findings. The results for the bed shear stress for the canyon area were 8 times greater than the outside and for eddy viscosity, 10 times higher. For the surroundings area, the eddy viscosity showed reasonable results with values around the regular 1.0 m2/s used for rivers. It is concluded that turbulent values can be calculated to better represent physical processes with the intention to improve hydrodynamic numerical models calibrations. Full article
(This article belongs to the Special Issue Turbulence in River and Maritime Hydraulics)
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10 pages, 1783 KiB  
Article
Dip Phenomenon in High-Curved Turbulent Flows and Application of Entropy Theory
by Donatella Termini and Tommaso Moramarco
Water 2018, 10(3), 306; https://doi.org/10.3390/w10030306 - 12 Mar 2018
Cited by 13 | Viewed by 3071
Abstract
The estimation of velocity profile in turbulent open channels is a difficult task due to the significant effects of the secondary flow. The present paper investigates the mechanism of the velocity-dip phenomenon, whereby the location of the maximum velocity appears to be below [...] Read more.
The estimation of velocity profile in turbulent open channels is a difficult task due to the significant effects of the secondary flow. The present paper investigates the mechanism of the velocity-dip phenomenon, whereby the location of the maximum velocity appears to be below the free surface. Previous studies conducted in straight channels relate the mechanism of the velocity-dip phenomenon to secondary flow induced by anisotropy of turbulence. This work focuses on high-curved channels where the secondary motion, which is also induced by the channel’s curvature, evolves along the bend. The width-to-depth ratio, B/h, is one of the most important parameters that are affecting the secondary motion entity. In particular, the present study aims to investigate the evolution of the velocity-dip along the bend for two values of the width-to-depth ratio and the applicability of the entropic model for the dip-phenomenon estimation. The results show that the velocity-dip is more accentuated for low values of the width-to-depth ratio, where the secondary motion plays a fundamental role in the distribution of the downstream flow velocity, although the velocity-dip is also present when the aspect ratio is higher than 10. Furthermore, the velocity profiles that were estimated by applying the entropic model are in good agreement with the measured ones, especially for B/h < 10. Full article
(This article belongs to the Special Issue Turbulence in River and Maritime Hydraulics)
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24 pages, 5330 KiB  
Article
Turbulence Measurement of Vertical Dense Jets in Crossflow
by Mouldi Ben Meftah and Michele Mossa
Water 2018, 10(3), 286; https://doi.org/10.3390/w10030286 - 08 Mar 2018
Cited by 12 | Viewed by 4147
Abstract
Turbulence measurement of a dense jet perpendicularly issued into a crossflow is investigated experimentally. The flow-velocity components were extensively measured with a high frequency Acoustic Doppler Velocimeter (ADV) system, whereas, a Micro Scale Conductivity Temperature instrument was used to measure the jet salinity. [...] Read more.
Turbulence measurement of a dense jet perpendicularly issued into a crossflow is investigated experimentally. The flow-velocity components were extensively measured with a high frequency Acoustic Doppler Velocimeter (ADV) system, whereas, a Micro Scale Conductivity Temperature instrument was used to measure the jet salinity. Special attention is given to understand the jet flow-structures in the flow symmetry plane. The flow velocity-fields, the jet trajectory, the turbulence intensities, the turbulent kinetic energy, the turbulent length scales, and the dispersion coefficients have been analyzed. The flow velocity-fields show that the dense jet is characterized by two distinct regions: an ascending region, of jet-like mixing, and a descending region of plume-like mixing. In this study, a new scaling approach of the jet trajectories, based on the jet characteristic length scales, is proposed, leading to an empirical closed-form expression to predict the jet trajectory. The turbulence analysis shows that the jet is accompanied by high levels of flow-turbulence intensities and large kinetic energy production. The results of the turbulent length scales indicate that the ambient flow-field, without jet effect, is an isotropic process. However, in the jet flow-field, a significant spatial-variation of the turbulent length scales was observed, indicating an anisotropic process. The trends of the dispersion coefficients follow those of the turbulent length scales. In comparison with the ambient flow, the jet flow-field shows a decrease of the longitudinal dispersion coefficient and an increase of the vertical one, leading to the increase of the jet width. Full article
(This article belongs to the Special Issue Turbulence in River and Maritime Hydraulics)
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16 pages, 2891 KiB  
Article
On the Hydrodynamic Geometry of Flow-Through versus Restricted Lagoons
by Nikolaos Th. Fourniotis, Georgios M. Horsch and Georgios A. Leftheriotis
Water 2018, 10(3), 237; https://doi.org/10.3390/w10030237 - 25 Feb 2018
Cited by 13 | Viewed by 4264
Abstract
The classification of a lagoon as a restricted lagoon is shown to depend not solely on its geometry but also on the tidal hydraulics. By numerically simulating the tidal exchange of two lagoons of similar geometrical dimensions, the Nidova lagoon and the Papas [...] Read more.
The classification of a lagoon as a restricted lagoon is shown to depend not solely on its geometry but also on the tidal hydraulics. By numerically simulating the tidal exchange of two lagoons of similar geometrical dimensions, the Nidova lagoon and the Papas lagoon, in Western Greece, subject to very similar tidal forcing, applied to the two tidal inlets in the first case and three in the second, very different residence times are found, namely 2.5 days for the Nidova and 25–30 days for the Papas lagoon. This large difference is attributed to the fact that whereas the Papas lagoon functions as a typical restricted lagoon, in which the water renewal is achieved by mixing in the lagoon of the tidal prism water exchanged within a tidal cycle, the Nidova lagoon functions as a flow-through system because of the differential arrival of the tide at its two tidal inlets. It is suggested that this way of enhancing the flushing rate of a lagoon be considered, whenever possible, when creating a new tidal inlet to the lagoon. Full article
(This article belongs to the Special Issue Turbulence in River and Maritime Hydraulics)
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4535 KiB  
Article
Invariants of Turbulence Reynolds Stress and of Dissipation Tensors in Regular Breaking Waves
by Sandro Longo, Maria Clavero, Luca Chiapponi and Miguel A. Losada
Water 2017, 9(11), 893; https://doi.org/10.3390/w9110893 - 16 Nov 2017
Cited by 19 | Viewed by 4386
Abstract
A series of measurements in a flume with a particle-tracking system in three dimensions applied to breaking waves is used to analyse the structure of turbulence with a full set of variables that usually are available only in numerical simulations. After extracting turbulence, [...] Read more.
A series of measurements in a flume with a particle-tracking system in three dimensions applied to breaking waves is used to analyse the structure of turbulence with a full set of variables that usually are available only in numerical simulations. After extracting turbulence, in addition to the standard analysis aiming to quantify the fluxes, i.e., the time-average and the phase-average levels of turbulence and vorticity (details are given in two former papers), a more in-depth description of the structure of turbulence Reynolds stress tensor is given, focussing on the invariants evolution in time and in the vertical. A relation between the components of the Reynolds stress tensor and of the dissipation tensor is depicted. This relation is finalised to possible models of turbulence in breaking waves. Full article
(This article belongs to the Special Issue Turbulence in River and Maritime Hydraulics)
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