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Experimental, Numerical and Field Approaches to Scour Research
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Experimental, Numerical and Field Approaches to Scour Research

A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Water Erosion and Sediment Transport".

Deadline for manuscript submissions: closed (31 August 2019) | Viewed by 60966

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

Special Issue Editors

Prof. Yee-Meng Chiew

E-Mail Website
Guest Editor
School of Civil and Environmental Engineering, Nanyang Technological University, Singapore 639798, Singapore
Interests: Scour, Sediment Transport, Turbulence, Seepage Effects, Structural Dynamics and Flow Interactions
Prof. Dr. Jihn-Sung Lai

E-Mail Website
Guest Editor
Hydrotech Research Institute/Department of Bioenvironmental Systems Engineering, National Taiwan University, Taipei 10617, Taiwan
Interests: bridge scour, sediment transport, monitoring and measurement, sensing network; flood inundation; river hydraulics
Prof. Oscar Link

E-Mail Website
Guest Editor
Department of Civil Engineering, Faculty of Engineering, Universidad de Concepción, Concepción 403000, Chile
Interests: Scour, Sediment Transport, Hydropower, Fishways Design, Floods Hydraulics, Rivers

Special Issue Information

Dear Colleagues,

Scientific research in the area of scour around hydraulic structures started around the middle of the 20th century. These works were primarily empirical in nature and founded on laboratory experiments because of the complexity of the flow–sediment–structure interactions. The pure laboratory empiricism of the earlier works has since been complemented by both numerical and field approaches, especially since numerical software and field measurement devices have attained a significantly higher level of sophistication. The three-pronged-approach towards scour research has provided new insights into this interesting topic, including not only the original bridge foundation scour but also propeller, submarine pipeline, monopile, jet, rock, river bank and levee scour, etc. The overall objective of this Special Issue is to present innovative research based on any one or a combination of these approaches. New knowledge is presented to elucidate the physics of the topic and provide solutions to practitioners, thus offering a better framework to aid the decision-making processes of river, coastal and offshore engineers. Contributions to this Special Issue relating to the study of the effect of turbulence on and dynamic behavior of the structures will be of great value for both academia and stakeholders. Finally, a collection of innovative papers that explore the wide spectrum of subjects relating to scour in one issue of the journal will be an indispensable platform for future research.

Prof. Yee-Meng Chiew
Prof. Jihn-Sung Lai
Prof. Oscar Link
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

  • Scour
  • Sediment Transport
  • Turbulence
  • River
  • Coastal
  • Offshore

Published Papers (15 papers)

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Editorial

Jump to: Research, Review

8 pages, 1139 KiB  
Editorial
Experimental, Numerical and Field Approaches to Scour Research
by Yee-Meng Chiew, Jihn-Sung Lai and Oscar Link
Water 2020, 12(6), 1749; https://doi.org/10.3390/w12061749 - 19 Jun 2020
Cited by 8 | Viewed by 2187
Abstract
Scour, which represents a fascinating and complex engineering problem involving a number of physical mechanisms and interactions, has motivated a vast amount of research following different but complementary methodological approaches such as experimental, numerical, and field methods. Far from being completely understood, scour [...] Read more.
Scour, which represents a fascinating and complex engineering problem involving a number of physical mechanisms and interactions, has motivated a vast amount of research following different but complementary methodological approaches such as experimental, numerical, and field methods. Far from being completely understood, scour remains one of the main hazards for many structures such as bridges, submarine pipelines, offshore wind turbines, etc. Thus, scour is currently a very active field of research with important open questions that are unanswered and practical challenges to be tackled. This Special Issue aims to bridge knowledge gaps by collecting fourteen papers to provide a wide view of scour types and different research approaches, with innovative ideas and inferences. Full article
(This article belongs to the Special Issue Experimental, Numerical and Field Approaches to Scour Research)
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Research

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15 pages, 3042 KiB  
Article
Examination of Blockage Effects on the Progression of Local Scour around a Circular Cylinder
by Priscilla Williams, Ram Balachandar and Tirupati Bolisetti
Water 2019, 11(12), 2631; https://doi.org/10.3390/w11122631 - 13 Dec 2019
Cited by 8 | Viewed by 2877
Abstract
An evaluation of scour estimation methods has indicated that the effects of blockage ratio are neglected in both scour modelling and development of new predictive methods. The role of channel blockage on the mechanism and progression of local scour is not well understood, [...] Read more.
An evaluation of scour estimation methods has indicated that the effects of blockage ratio are neglected in both scour modelling and development of new predictive methods. The role of channel blockage on the mechanism and progression of local scour is not well understood, and further analysis is required in order to incorporate this effect into scour estimation. In the present investigation, local scour experiments were carried out under varying blockage ratio. The results were compared with data from literature in order to explore the effects of blockage ratio (D/b, where D is the pier diameter, and b is the channel width) on equilibrium scour depth (dse/D, where dse is the depth of scour at equilibrium). It was determined that D/b had a small influence on both dse/D and the progression of scour depth (ds/D) when relative coarseness D/d50 < 100 (where d50 is the median diameter of sediment), and that the influence appeared to be amplified when D/d50 > 100. The efficacy of scour estimation methods used to predict the progression of local scour was also dependent on D/d50. A method of scour estimation used to predict dse/D was evaluated, and it was similarly found to be particularly effective when D/d50 < 100. In future work, further experiments and analysis in the range of D/d50 > 100 are required in order to establish the role of D/b under prototype conditions and to refine existing scour estimation methods. Full article
(This article belongs to the Special Issue Experimental, Numerical and Field Approaches to Scour Research)
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30 pages, 9609 KiB  
Article
Numerical Study of the Hydrodynamics of Waves and Currents and Their Effects in Pier Scouring
by Matias Quezada, Aldo Tamburrino and Yarko Niño
Water 2019, 11(11), 2256; https://doi.org/10.3390/w11112256 - 28 Oct 2019
Cited by 15 | Viewed by 3427
Abstract
The scour around cylindrical piles due to codirectional and opposite waves and currents is studied with Reynolds Averaged Navier–Stokes (RANS) equations via REEF3D numeric modeling. First, a calibration process was made through a comparison with the experimental data available in the literature. Subsequently, [...] Read more.
The scour around cylindrical piles due to codirectional and opposite waves and currents is studied with Reynolds Averaged Navier–Stokes (RANS) equations via REEF3D numeric modeling. First, a calibration process was made through a comparison with the experimental data available in the literature. Subsequently, not only the hydrodynamics, but also the expected scour for a set of scenarios, which were defined by the relative velocity of the current ( U C W ), were studied numerically. The results obtained show that the hydrodynamics around the pile for codirectional or opposite waves and currents not have significant differences when analyzed in terms of their velocities, vorticities and mean shear stresses, since the currents proved to be more relevant compared to the net flow. The equilibrium scour, estimated by the extrapolation of the numerical data with the equation by Sheppard, enabled us to estimate values close to those described in the literature. From this extrapolation, it was verified that the dimensionless scour would be less when the waves and currents are from opposite directions. The U C W parameter is an indicator used to adequately measure the interactions between the currents and waves under conditions of codirectional flow. Nevertheless, it is recommended to modify this parameter for currents and waves in opposite directions, and an equation is proposed for this case. Full article
(This article belongs to the Special Issue Experimental, Numerical and Field Approaches to Scour Research)
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20 pages, 6884 KiB  
Article
Scouring of Replenished Sediment through Reservoir Flood Discharge Affects Suspended Sediment Concentrations at Downstream River Water Intake
by Fong-Zuo Lee, Jihn-Sung Lai, Wen-Dar Guo and Tetsuya Sumi
Water 2019, 11(10), 1998; https://doi.org/10.3390/w11101998 - 25 Sep 2019
Cited by 7 | Viewed by 3973
Abstract
Dredging is a commonly used sedimentation management strategy to remove mechanically deposited sediment from reservoirs. However, dredged sediment disposal is costly. Dredged sediment can be considered a beneficial resource and used for riverbed replenishment to prevent downstream riverbed degradation and improve aquatic habitats. [...] Read more.
Dredging is a commonly used sedimentation management strategy to remove mechanically deposited sediment from reservoirs. However, dredged sediment disposal is costly. Dredged sediment can be considered a beneficial resource and used for riverbed replenishment to prevent downstream riverbed degradation and improve aquatic habitats. This study investigated the feasibility of using dredged deposits with cohesive sediment for replenishment at the Shihmen Reservoir. Using the criterion of critical scour velocity, we conducted hydraulic assessments and identified the feasible replenishment area as the experimental domain. A physical model was developed to mimic the scouring process in the replenishment area. By applying dynamic similarity for scouring fine replenished sediment, we derived the regression relationship between flow-critical velocity and sediment-dry density, and used it for model ratio scaling of the grain size, dry density, and concentration in the physical model. Scoured sediment concentrations were measured to study the scour ratio at various flood discharges. Experimental results indicated that the scour ratio was related to factors such as flood discharge, flood duration, and water content of the replenished sediment. The reduction ratio of the concentration of sediment scoured from the replenishment area to the concentration of sediment at the downstream water intake was approximately 90% in the present study. Full article
(This article belongs to the Special Issue Experimental, Numerical and Field Approaches to Scour Research)
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10 pages, 4265 KiB  
Article
Case Study: Model Test on the Effects of Grade Control Datum Drop on the Upstream Bed Morphology in Shiting River
by Xudong Ma, Lu Wang, Ruihua Nie, Kejun Yang and Xingnian Liu
Water 2019, 11(9), 1898; https://doi.org/10.3390/w11091898 - 11 Sep 2019
Cited by 5 | Viewed by 2606
Abstract
This paper conducted an undistorted scaled model test (geometric scale λL = 1:80; the others are derived scales based on Froude similitude) of a 1.3 km-long river reach in Shiting River, China, investigating the impacts of the grade control datum (GCD, defined [...] Read more.
This paper conducted an undistorted scaled model test (geometric scale λL = 1:80; the others are derived scales based on Froude similitude) of a 1.3 km-long river reach in Shiting River, China, investigating the impacts of the grade control datum (GCD, defined as the crest elevation of the grade control structure) drop on the upstream bed morphology. Three GCDs and six flood events (occurrence probability 1–50%, discharge = 600–4039 m3/s) were tested on the model. Experimental results indicate that, for a constant GCD, the increase in discharge deepens and widens the upstream river bed. For a lower GCD, the increase in channel depth and width caused by the increasing discharge is greater. For each discharge, the decrease in GCD induces a lower and steeper upstream river bed, widening the upstream main channel. For lower discharge, the GCD drop induces a head cut erosion area upstream of the grade control structure and the head cut erosion area is filled by the upstream sediment when the flow discharge is high. Experimental data also indicate that the maximum general scour depth at the 105th Provincial Highway Bridge is approximately independent of discharge for a constant GCD. For a lower GCD, the general scour depth at the 105th Provincial Highway Bridge increases slightly with discharge. Full article
(This article belongs to the Special Issue Experimental, Numerical and Field Approaches to Scour Research)
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10 pages, 15387 KiB  
Article
Scour Evolution Downstream of Submerged Weirs in Clear Water Scour Conditions
by Dawei Guan, Jingang Liu, Yee-Meng Chiew and Yingzheng Zhou
Water 2019, 11(9), 1746; https://doi.org/10.3390/w11091746 - 22 Aug 2019
Cited by 12 | Viewed by 3827
Abstract
Although weirs or dikes in the riverine and coastal environments are frequently overtopped, few studies have hitherto examined the evolution of the scour process downstream of these structures under the submerged condition. This paper presents an experimental investigation on time evolution of the [...] Read more.
Although weirs or dikes in the riverine and coastal environments are frequently overtopped, few studies have hitherto examined the evolution of the scour process downstream of these structures under the submerged condition. This paper presents an experimental investigation on time evolution of the scour process downstream of submerged weirs with a uniform coarse sand. The clear-water scour experiments were carried out in a tilting recirculation flume. Different flow intensities and overtopping ratios (approach flow depth/weir height) were adopted in the experiments. Experimental observations show that the scour hole downstream of submerged weirs develops very fast in the initial stage, before progressing at a decreasing rate and eventually reaching the equilibrium stage. The results show that an increase of the overtopping ratio or flowrate can generate larger scour depth and volume downstream of the weir. Moreover, geometrical similarity of the scour hole that formed downstream of the weir was observed in the tests. Finally, empirical equations for predicting scour hole geometrical evolutions downstream of the submerged weirs were presented. The results of this study are useful in the development of numerical/analytical models capable of estimating the scour depth downstream of weirs in the river or coastal areas, for which the overtopping conditions are present. Full article
(This article belongs to the Special Issue Experimental, Numerical and Field Approaches to Scour Research)
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17 pages, 1906 KiB  
Article
Two-Phase Flow Simulation of Tunnel and Lee-Wake Erosion of Scour below a Submarine Pipeline
by Antoine Mathieu, Julien Chauchat, Cyrille Bonamy and Tim Nagel
Water 2019, 11(8), 1727; https://doi.org/10.3390/w11081727 - 19 Aug 2019
Cited by 21 | Viewed by 5197
Abstract
This paper presents a numerical investigation of the scour phenomenon around a submarine pipeline. The numerical simulations are performed using SedFoam, a two-phase flow model for sediment transport implemented in the open source Computational Fluid Dynamics (CFD) toolbox OpenFOAM. The paper focuses on [...] Read more.
This paper presents a numerical investigation of the scour phenomenon around a submarine pipeline. The numerical simulations are performed using SedFoam, a two-phase flow model for sediment transport implemented in the open source Computational Fluid Dynamics (CFD) toolbox OpenFOAM. The paper focuses on the sensitivity of the granular stress model and the turbulence model with respect to the predictive capability of the two-phase flow model. The quality of the simulation results is estimated using a statistical estimator: the Brier Skill Score. The numerical results show no sensitivity to the granular stress model. However, the results strongly depend on the choice of the turbulence model, especially through the different implementations of the cross-diffusion term in the dissipation equation between the k − ε and the k − ω 2006 models. The influence of the cross-diffusion term tends to indicate that the sediment transport layer behaves more as a shear layer than as a boundary layer, for which the k − ε model is more suitable. Full article
(This article belongs to the Special Issue Experimental, Numerical and Field Approaches to Scour Research)
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17 pages, 3601 KiB  
Article
Turbulent Flow Structures and Scour Hole Characteristics around Circular Bridge Piers over Non-Uniform Sand Bed Channels with Downward Seepage
by Rutuja Chavan, Paola Gualtieri and Bimlesh Kumar
Water 2019, 11(8), 1580; https://doi.org/10.3390/w11081580 - 30 Jul 2019
Cited by 13 | Viewed by 4050
Abstract
In alluvial rivers bridge piers often cause local scour, a complex phenomenon as a result of the interaction between turbulent flow and bed material. In this paper, the results of an experimental study on the scour hole characteristics around single vertical pier sets [...] Read more.
In alluvial rivers bridge piers often cause local scour, a complex phenomenon as a result of the interaction between turbulent flow and bed material. In this paper, the results of an experimental study on the scour hole characteristics around single vertical pier sets on a non-uniform sand bed, under no seepage, and with downward seepage conditions, are described. In case of downward seepage, turbulent statistics, such as Reynolds stress, higher order moments, TKE-flux, and consequently sediment transport, decrease upstream of the pier, while increasing on both sides of it, where the enhanced erosive capacity of the flow results in an increase in the scour hole width. Moreover, the scour hole length shifts downstream. Empirical equations for the evaluation of scour hole characteristics, such as the length, width, area, and volume, including the downward seepage parameter, are proposed and experimentally tested. Model predictions give reasonably good agreement with the experimental data. Full article
(This article belongs to the Special Issue Experimental, Numerical and Field Approaches to Scour Research)
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17 pages, 10715 KiB  
Article
Vortex Evolution within Propeller Induced Scour Hole around a Vertical Quay Wall
by Maoxing Wei, Nian-Sheng Cheng, Yee-Meng Chiew and Fengguang Yang
Water 2019, 11(8), 1538; https://doi.org/10.3390/w11081538 - 25 Jul 2019
Cited by 7 | Viewed by 3154
Abstract
This paper presents an experimental study on the characteristics of the propeller-induced flow field and its associated scour hole around a closed type quay (with a vertical quay wall). An “oblique particle image velocimetry” (OPIV) technique, which allows a concurrent measurement of the [...] Read more.
This paper presents an experimental study on the characteristics of the propeller-induced flow field and its associated scour hole around a closed type quay (with a vertical quay wall). An “oblique particle image velocimetry” (OPIV) technique, which allows a concurrent measurement of the velocity field and scour profile, was employed in measuring the streamwise flow field (jet central plane) and the longitudinal centerline scour profile. The asymptotic scour profiles obtained in this study were compared with that induced by an unconfined propeller jet in the absence of any berthing structure, which demonstrates the critical role of the presence of the quay wall as an obstacle in shaping the scour profile under the condition of different wall clearances (i.e., longitudinal distance between propeller and wall). Moreover, by comparing the vortical structure within the asymptotic scour hole around the vertical quay wall with its counterpart in the case of an open quay (with a slope quay wall), the paper examines the effect of quay types on the formation of the vortex system and how it determines the geometrical characteristic of the final scour profile. Furthermore, the temporal development of the mean vorticity field and the vortex system are discussed in terms of their implications on the evolution of the scour hole. In particular, comparison of the circulation development of the observed vortices allows a better understanding of the vortex scouring mechanism. Energy spectra analysis reveals that at the vortex centers, their energy spectra distributions consistently follow the −5/3 law throughout the entire scouring process. As the scour process evolves, the turbulent energy associated with the near-bed vortex, which is responsible for scouring, is gradually reduced, especially for the small-scale eddies, indicating a contribution of the dissipated turbulent energy in excavating the scour hole. Finally, a comparison of the near-bed flow characteristics of the average kinetic energy (AKE), turbulent kinetic energy (TKE), and Reynolds shear stress (RSS) are also discussed in terms of their implications for the scour hole development. Full article
(This article belongs to the Special Issue Experimental, Numerical and Field Approaches to Scour Research)
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17 pages, 6905 KiB  
Article
Local Scour at Complex Bridge Piers in Close Proximity under Clear-Water and Live-Bed Flow Regime
by Yifan Yang, Bruce W. Melville, Graham H. Macky and Asaad Y. Shamseldin
Water 2019, 11(8), 1530; https://doi.org/10.3390/w11081530 - 24 Jul 2019
Cited by 18 | Viewed by 5702
Abstract
In this study, we investigated the characteristics of scour at complex bridge piers in close proximity. The experiments were performed under both clear-water and live-bed flow regimes. We compare our results with those for a single complex pier. Further, the performance of existing [...] Read more.
In this study, we investigated the characteristics of scour at complex bridge piers in close proximity. The experiments were performed under both clear-water and live-bed flow regimes. We compare our results with those for a single complex pier. Further, the performance of existing predictors is discussed. In this study, four typical pier arrangements were adopted, including side-by-side with aligned or 30° skewed flow, staggered, and tandem. The results show that the skew angle for a side-by-side arrangement significantly accelerates the clear-water scour development at all the vertical piles as well as between the piers, and the most scoured pile shifts from the upstream end to the downstream end of the upstream pier flank. The staggered and tandem pier arrangement show significant protection to the downstream pier for both the developing rate and the equilibrium scour depth. When the flow velocity exceeds the threshold for general bed motion, the clear-water scour pattern for all the pier arrangements may be altered significantly due to the upstream sediment supply, the weakened protection effect, and the enhanced flow contraction. The bed-forms migrate via the bridge opening and are damped gradually by the flow, and thus the response of the bed morphology under live-bed conditions is quite unsteady. Full article
(This article belongs to the Special Issue Experimental, Numerical and Field Approaches to Scour Research)
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19 pages, 8206 KiB  
Article
Experimental Investigation of Local Scour Protection for Cylindrical Bridge Piers Using Anti-Scour Collars
by Shunyi Wang, Kai Wei, Zhonghui Shen and Qiqi Xiang
Water 2019, 11(7), 1515; https://doi.org/10.3390/w11071515 - 21 Jul 2019
Cited by 55 | Viewed by 6447
Abstract
Local scour of bridge piers is one of the main threats responsible for bridge damage. Adopting scour countermeasures to protect bridge foundations from scour has become an important issue for the design and maintenance of bridges located in erodible sediment beds. This paper [...] Read more.
Local scour of bridge piers is one of the main threats responsible for bridge damage. Adopting scour countermeasures to protect bridge foundations from scour has become an important issue for the design and maintenance of bridges located in erodible sediment beds. This paper focuses on the protective effect of one active countermeasure named an “anti-scour collar” on local scour around the commonly used cylindrical bridge pier. A cylindrical pier model was set up in a current flume. River sand with a median particle size of 0.324 mm was selected and used as the sediment in the basin. A live-bed scour experimental program was carried out to study the protective effect of an anti-scour collar by comparing the local scour at a cylindrical bridge pier model with and without collar. The effects of three design parameters including collar installation height, collar external diameter and collar protection range, on the scour depth and scour development were investigated parametrically. According to the experimental results, it can be concluded that: the application of an anti-scour collar alleviates the local scour at the pier effectively; and the protection effect decreases with an increase in the collar installation height, but increases with an increase in the collar external diameter and the protection range. Design suggestions for improving the scour protective effect of the anti-scour collar are summarized and of great practical guiding significance to the development of anti-scour collars for bridge piers. Full article
(This article belongs to the Special Issue Experimental, Numerical and Field Approaches to Scour Research)
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16 pages, 5014 KiB  
Article
Visible Light Communication System for Offshore Wind Turbine Foundation Scour Early Warning Monitoring
by Yung-Bin Lin, Tzu-Kang Lin, Cheng-Chun Chang, Chang-Wei Huang, Ben-Ting Chen, Jihn-Sung Lai and Kuo-Chun Chang
Water 2019, 11(7), 1486; https://doi.org/10.3390/w11071486 - 17 Jul 2019
Cited by 7 | Viewed by 2968
Abstract
Offshore wind farms have a superior wind source to terrestrial wind farms, but they also face more severe environmental conditions such as severe storms, typhoons, and sea waves. Scour leads to the excavation of sediments around the foundations of structures, reducing the safe [...] Read more.
Offshore wind farms have a superior wind source to terrestrial wind farms, but they also face more severe environmental conditions such as severe storms, typhoons, and sea waves. Scour leads to the excavation of sediments around the foundations of structures, reducing the safe capacity of the structures. The phenomenon of pier scour is extremely complex because of the combined effects of the vortex system involving time-dependent flow patterns and sediment transport mechanisms. A real-time scour monitoring system can improve the safety of structures and afford cost-effective operations by preventing premature or unnecessary maintenance. This paper proposes an on-site scour monitoring system using visible light communication (VLC) modules for offshore wind turbine installations. A flume experiment revealed that the system was highly sensitive and accurate in monitoring seabed scour processes. This arrayed-VLC sensory system, proposed in this paper, has considerable potential for safety monitoring and also can contribute to improving the accuracy of empirical scour formulas for sustainable maintenance in the life cycle of offshore structures. Full article
(This article belongs to the Special Issue Experimental, Numerical and Field Approaches to Scour Research)
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19 pages, 6461 KiB  
Article
Scour Induced by Single and Twin Propeller Jets
by Yonggang Cui, Wei Haur Lam, Tianming Zhang, Chong Sun and Gerard Hamill
Water 2019, 11(5), 1097; https://doi.org/10.3390/w11051097 - 25 May 2019
Cited by 13 | Viewed by 4610
Abstract
Single and twin ship propeller jets produce scour holes with deposition dune. The scour hole has a maximum depth at a particular length downstream within the propeller jet. Existing equations are available to predict maximum scour depth and the corresponding scour length downstream. [...] Read more.
Single and twin ship propeller jets produce scour holes with deposition dune. The scour hole has a maximum depth at a particular length downstream within the propeller jet. Existing equations are available to predict maximum scour depth and the corresponding scour length downstream. Experiments conducted with various physical propeller models, rotational speeds, propeller-to-propeller distances and bed clearances are presented. The measurements allowed a better understanding of the mechanism of temporal scour and deposition formation for scour caused by single-propeller and twin-propeller. Results show that the propeller jet scour profiles can be divided into three zones, which are the small scour hole, primary scour hole and deposition dune. An empirical 2D scour model is proposed to predict the scour profile for both a single-propeller and twin-propeller using a Gaussian normal distribution. Full article
(This article belongs to the Special Issue Experimental, Numerical and Field Approaches to Scour Research)
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21 pages, 3634 KiB  
Article
Temporal Evolution of Seabed Scour Induced by Darrieus-Type Tidal Current Turbine
by Chong Sun, Wei Haur Lam, Su Shiung Lam, Ming Dai and Gerard Hamill
Water 2019, 11(5), 896; https://doi.org/10.3390/w11050896 - 28 Apr 2019
Cited by 9 | Viewed by 2776
Abstract
The temporal evolution of seabed scour was investigated to prevent damage around a monopile foundation for Darrieus-type tidal current turbine. Temporal scour depths and profiles at various turbine radius and tip clearances were studied by using the experimental measurements. Experiments were carried out [...] Read more.
The temporal evolution of seabed scour was investigated to prevent damage around a monopile foundation for Darrieus-type tidal current turbine. Temporal scour depths and profiles at various turbine radius and tip clearances were studied by using the experimental measurements. Experiments were carried out in a purpose-built recirculating water flume associated with 3D printed turbines. The scour hole was developed rapidly in the initial process and grew gradually. The ultimate equilibrium of scour hole was reached after 180 min. The scour speed increased with the existence of a rotating turbine on top of the monopile. The findings suggested that monopile foundation and the rotating turbine are two significant considerations for the temporal evolution of scour. The scour depth is inversely correlated to the tip-bed clearance between the turbine and seabed. Empirical equations were proposed to predict the temporal scour depth around turbine. These equations were in good agreement with the experimental data. Full article
(This article belongs to the Special Issue Experimental, Numerical and Field Approaches to Scour Research)
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Review

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22 pages, 6823 KiB  
Review
Scour at Bridge Foundations in Supercritical Flows: An Analysis of Knowledge Gaps
by Oscar Link, Emmanuel Mignot, Sebastien Roux, Benoit Camenen, Cristián Escauriaza, Julien Chauchat, Wernher Brevis and Salvatore Manfreda
Water 2019, 11(8), 1656; https://doi.org/10.3390/w11081656 - 10 Aug 2019
Cited by 11 | Viewed by 6241
Abstract
The scour at bridge foundations caused by supercritical flows is reviewed and knowledge gaps are analyzed focusing on the flow and scour patterns, available measuring techniques for the laboratory and field, and physical and advanced numerical modeling techniques. Evidence suggests that the scour [...] Read more.
The scour at bridge foundations caused by supercritical flows is reviewed and knowledge gaps are analyzed focusing on the flow and scour patterns, available measuring techniques for the laboratory and field, and physical and advanced numerical modeling techniques. Evidence suggests that the scour depth caused by supercritical flows is much smaller than expected, by an order of magnitude compared to that found in subcritical flows, although the reasons for this behavior remain still unclear. Important questions on the interaction of the horseshoe vortex with the detached hydraulic-jump and the wall-jet flow observed in supercritical flows arise, e.g., does the interaction between the flow structures enhance or debilitate the bed shear stresses caused by the horseshoe vortex? What is the effect of the Froude number of the incoming flow on the flow structures around the foundation and on the scour process? Recommendations are provided to develop and adapt research methods used in the subcritical flow regime for the study of more challenging supercritical flow cases. Full article
(This article belongs to the Special Issue Experimental, Numerical and Field Approaches to Scour Research)
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