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Artykuły w czasopismach na temat „LOCAL SCAUR”

Autor: Grafiati

Data publikacji: 11 września 2023

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1

Puricelli, Martín, Pablo Spalletti i Agnes Paterson. "Estudio de erosión local en grupos de Pilas Cuadradas". Aqua-LAC 6, nr 1 (31.03.2014): 25–32. http://dx.doi.org/10.29104/phi-aqualac/2014-v6-1-04.

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Con el objeto de realizar experiencias relativas a la erosión local en grupo de pilas, para los casos menos estudiados pero de aplicación práctica, se trabajó con dos pilas de sección cuadrada. Se realizaron ensayos a fondo móvil en un canal de dos metros de ancho en condiciones de agua clara, sin transporte de sedimento aguas arriba de estas estructuras para evitar las complejidades propias de las formas de fondo. Se exploraron una variedad de condiciones experimentales con diferentes tirantes (entre 30 y 50 cm), espaciamiento entre pilas y la configuración de las mismas. Las pilas tienen 20 cm de lado. En un caso, ambas pilas están alineadas a la corriente y en el segundo caso que denominamos al tresbolillo, las pilas están desplazadas lateralmente una respecto de la otra. En este trabajo se analizan las erosiones máximas medidas, el campo de velocidades alrededor de las pilas y el relevamiento batimétrico del lecho del canal. Las erosiones máximas medidas se compararon con diferentes fórmulas de predicción. Se estudió la evolución temporal de la erosión comparándola con ensayos similares de larga duración pero con una única pila, analizándose también el ajuste de formulaciones predictivas del avance de la socavación en el tiempo. En todos los casos se observó una dependencia de la erosión máxima respecto de la separación entre pilas para los grupos de pilas alineadas. Esta erosión es sobreestimada con la fórmula del HEC-18 para la geometría en tresbolillo. Estos efectos de conjunto para las pilas alineadas se manifiestan desde los primeros minutos de las experiencias. Para la geometría en tresbolillo se observó un cambio en la curvatura de la evolución temporal de la erosión que se puede asociar justamente a estos efectos de conjunto.

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2

Kim. "Prediction of Local Scour Around Bridge Piers Using GEP Model". Journal of the Korean Society of Civil Engineers 34, nr 6 (2014): 1779. http://dx.doi.org/10.12652/ksce.2014.34.6.1779.

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3

Mohamed, M. S., i J. A. Mccorquodale. "Short-term local scour". Journal of Hydraulic Research 30, nr 5 (wrzesień 1992): 685–99. http://dx.doi.org/10.1080/00221689209498888.

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4

Jaramillo-Mejía, Paul, i Jorge Reyes-Salazar. "Evaluación del efecto del paramento inclinado de pilares en la socavación local". Tecnología y ciencias del agua 10, nr 5 (1.09.2019): 106–25. http://dx.doi.org/10.24850/j-tyca-2019-05-04.

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5

Xie, Liquan, Yehui Zhu, Huang Li, Yan-hong Li, Yuanping Yang i Tsung-chow Su. "Local Scour Near Flexible Flow Deflectors". Water 12, nr 1 (4.01.2020): 153. http://dx.doi.org/10.3390/w12010153.

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Rigid flow deflectors are usually used on water flow beds to protect engineering structures such as breakwater in coasts and to regulate flow routes in open channels. To reduce its side-effects, i.e., local scour at the toe of deflectors, a flexible flow deflector is proposed, and the corresponding local scour was investigated in this study. A flume experiment was conducted to investigate local scour. To show the advantage of flexible deflectors, a control experimental test was also conducted using a traditional rigid deflector under the same blockage area configuration and the same flow conditions. The flow field near the flexible deflector was also measured to reveal the local flow field. The results show that the bed-scour develops near the toe edges of both flexible and rigid deflectors, but the maximum and averaged scour depths for the flexible deflector are smaller. This advantage of flexible deflector in scour depth is mainly caused by its prone posture, which induces the upward stretching and enlarging horizontally rotating vortex and the upward shifted vertically rotating vortex. The former dissipates more turbulent energy and the latter results in smaller bed shear stress, which lead to smaller scour depth directly. In addition, the up- and down-swaying movement of the flexible deflector can also assistant to dissipate more turbulent energy, thereby damping the intense of the horseshoe vortices and thus weakening scour depth as well. The results of this study provide an elementary understanding on the mechanisms of a flexible flow structure and an alternative deflector-device to reduce scour depth.

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6

HUSAIN, D., A. QURAISHI i A. ALIBRAHIM. "Local Scour at Bridge Abutments". Journal of King Abdulaziz University-Engineering Sciences 10, nr 1 (1998): 141–53. http://dx.doi.org/10.4197/eng.10-1.10.

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7

Sheppard, D. Max. "Overlooked Local Sediment Scour Mechanism". Transportation Research Record: Journal of the Transportation Research Board 1890, nr 1 (styczeń 2004): 107–11. http://dx.doi.org/10.3141/1890-13.

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8

Melville, B. W. "Local Scour at Bridge Abutments". Journal of Hydraulic Engineering 118, nr 4 (kwiecień 1992): 615–31. http://dx.doi.org/10.1061/(asce)0733-9429(1992)118:4(615).

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9

Ettema, R., E. A. Mostafa, B. W. Melville i A. A. Yassin. "Local Scour at Skewed Piers". Journal of Hydraulic Engineering 124, nr 7 (lipiec 1998): 756–59. http://dx.doi.org/10.1061/(asce)0733-9429(1998)124:7(756).

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10

Chiew, Y. M., i B. W. Melville. "Local scour around bridge piers". Journal of Hydraulic Research 25, nr 1 (styczeń 1987): 15–26. http://dx.doi.org/10.1080/00221688709499285.

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11

Khanbilvardi, R. M., M. W. Akhtar i A. S. Rogowski. "LOCAL SCOUR AROUND CYLINDRICAL OBJECTS". Journal of the American Water Resources Association 24, nr 4 (sierpień 1988): 839–45. http://dx.doi.org/10.1111/j.1752-1688.1988.tb00935.x.

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12

Sang, Liansheng, Jun Wang, Tiejie Cheng, Zhixing Hou i Jueyi Sui. "Local Scour around Tandem Double Piers under an Ice Cover". Water 14, nr 7 (6.04.2022): 1168. http://dx.doi.org/10.3390/w14071168.

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Compared to the scour around a single pier, the local scour process around tandem double piers is much more complicated. Based on laboratory experiments in a flume, we conducted the scour process around tandem double piers under an ice-covered flow condition. The results showed that when the pier spacing ratio L/D = 2 (where L = the pier spacing distance, and D = the pier diameter), the rear pier (the downstream one) will intensify the horseshoe vortex process behind the front pier, and the scour depth around the front pier will increase by about 10%. As the pier spacing ratio L/D increases, the scour depth around the front pier will gradually decrease. When the pier spacing ratio L/D = 5, sediment scoured around the front pier begins to deposit between these two piers. To initiate a deposition dune between piers, the pier spacing distance under an ice-covered condition is about 20% more than that under an open flow condition. The results also showed that the existence of the rear pier will lead to an increase in the length of the scour hole but a decrease in the depth of the scour hole around the front pier. The local scour around the front pier interacts with the local scour of the rear pier. The maximum scour depth of the scour hole around the rear pier increases first, then decreases and increases again afterward. When the pier spacing ratio L/D = 9, the scour depth around the rear pier is the least. With an increase in the pier spacing ratio, the influence of the local scour around the front pier on the local scour around the rear pier gradually decreases. When the pier spacing ratio L/D is more than 17, the scour around the front pier has hardly any influence on that around the rear pier. The scour depth around the rear pier is about 90% of that around the front pier.

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13

McGovern, David J., Suzana Ilic, Andrew M. Folkard, Stuart J. McLelland i Brendan J. Murphy. "EVOLUTION OF LOCAL SCOUR AROUND A COLLARED MONOPILE THROUGH TIDAL CYCLES". Coastal Engineering Proceedings 1, nr 33 (15.12.2012): 113. http://dx.doi.org/10.9753/icce.v33.sediment.113.

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This paper presents the results of an experiment designed to assess the time-development of scour around an offshore wind turbine collared monopile over a number of tidal cycles. One collar shape and location was investigated. The scour developed more slowly and the scour depth was shallower than for the case of a smooth monopile throughout the majority of the first half-cycle. This difference reduced quite rapidly during the second half-cycle and the scour depth at the end of two tidal cycles was essentially the same as for the smooth monopile. The time development of the scour was compared with results from existing empirical models for the time-development of scour under unidirectional flow. As expected, these models give a much smoother evolution of scour and different scour rates than those measured. Time variation in scour depth was better reproduced with a simplified approach for prediction of the time-varying development of scour. This also highlighted a problem with estimation of the time scale for the development of the equilibrium scour depth. Further investigations are needed before this alternative scour protection is completely rejected.

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14

Clark, J. Madison, i Tom D. Wang. "Local Flaps in Scar Revision". Facial Plastic Surgery 17, nr 04 (2001): 295–308. http://dx.doi.org/10.1055/s-2001-18831.

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15

Khassaf, Saleh I., i Mohammed Ridha Sadeq. "Experimental Study of Local Scour around Circular pier Fitted with Collar". Kufa Journal of Engineering 3, nr 2 (26.05.2014): 87–100. http://dx.doi.org/10.30572/2018/kje/321259.

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Scour is defined as the erosion of streambed sediment around an obstruction in a flow field. Bridge pier scouring is a significant problem in the safety estimation of bridges. In this study, the use of rectangular collar for reducing the effect of local scour at a circular pier in a laboratory flume was presented. The study was conducted using 6.6 m laboratory flume in length and 0.4 m in width. Experiments were conducted for various sizes of rectangular collars fitted at the bed elevation on the scour depth at the circular pier with clear-water scour condition. The time development of scour depth at the circular pier with and without a collar of circular installed was conducted. In collars observed that size of a collar plate increases, the scour decreases. Results showed that the maximum reduction in scour depth equal to 100% (no scour hole). Dimensional analysis technique was used, and from the experimental data an empirical formula was derived. It was found that the predicated scour depth from the formula performs well as compared to the observed scour depth.

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16

Hafez, Youssef I. "Mathematical Modeling of Local Scour at Slender and Wide Bridge Piers". Journal of Fluids 2016 (14.06.2016): 1–19. http://dx.doi.org/10.1155/2016/4835253.

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Most existing equations for predicting local scour at bridge piers suffer from overprediction of the scour depths which results in higher foundation costs. To tackle this problem, a mathematical model for predicting bridge pier scour is developed herein based on an energy balance theory. The present study equation was compared to commonly used bridge scour equations using scour field data in USA. The developed equation has several advantages among which we have the following: it adds to the understanding of the physics of bridge pier scour, is valid for slender and wide piers, does not suffer from overprediction of scour depths, addresses clear water and live bed scour, and includes the effects of various characteristics of the bed material such as specific gravity (or density), porosity, size, and angle of repose. In addition, the developed equation accounts for the debris effect and aids in the design of scour mitigation methods such as collars, side bars, slots, and pier protective piles.

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17

Oh, Hyun Sik, i Ho Jin Lee. "Characteristics of Local Scour Around the Double Pile in Waves". Journal of Korean Society of Coastal and Ocean Engineers 34, nr 5 (31.10.2022): 169–75. http://dx.doi.org/10.9765/kscoe.2022.34.5.169.

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Scour in a flow field affected by waves, such as river estuaries or shallow waters, is more difficult to predict than scour in a currents. The main issue in predicting the scour around circular files, such as undersea bridges, is the maximum scour depth and the point of occurrence. In the case of two or more adjacent circular piles, the location and depth of maximum scour according to the spacing between piles and the arrangement method show a lot of difference compared to the case of a single pile. In this paper, the KC number are calculated as dimensionless variables representing the strength of the flow. And the correlation between pile gap size and relative scour depth was analyzed.

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18

Hassan, Zahraa F., Ibtisam R. Karim i Abdul-Hassan K. Al-Shukur. "Effect of Interaction between Bridge Piers on Local Scouring in Cohesive Soils". Civil Engineering Journal 6, nr 4 (1.04.2020): 659–69. http://dx.doi.org/10.28991/cej-2020-03091498.

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Local scour at the piers is one of the main reasons of bridge foundation undermining. Earlier research studies focused mainly on the scour at a single bridge pier; nevertheless, modern designs of the bridges comprise wide-span and thus group of piers rather than a single pier are usually used to support the superstructure. The flow and scour pattern around group of piers is different from the case of a single pier due to the interaction effect. Reviewing the literature of local scour around bridge piers group revealed that the local scour around bridge piers group founded in cohesive soil bed was not investigated, and most of the scour studies were related to scour in cohesionless soils. The objective of the present study is to investigate the effect of the interaction between two in-line (tandem) circular bridge piers of variable spacings founded in cohesive soil on the local scour. A set of laboratory flume experiments were conducted under the clear-water scour condition to investigate this effect. This study is the first that investigates experimentally the scour around group of bridge piers in cohesive bed. It was found that the maximum scour depth at the upstream pier of the two in-line piers occurred at a spacing of two times the diameter of the pier, scour at the downstream pier was reduced due to a sheltering effect, the interference effect will be reduced for pier spacings larger than three times of the pier diameter. A recent pier scour equation was used to estimate the scour depths at the two in-line piers in cohesive soil and compare the estimated value with the measured scour depths in the laboratory. The comparison indicated that the proposed scour equation overestimates the scour depths at both the upstream and the downstream pier.

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19

Nasrollahi, A., M. Ghodsian i S. A. A. Salehi Neyshabour. "Local Scour at Permeable Spur Dikes". Journal of Applied Sciences 8, nr 19 (15.09.2008): 3398–406. http://dx.doi.org/10.3923/jas.2008.3398.3406.

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20

Karki, R., M. A. A. Faruque i R. Balachandar. "Local scour by submerged offset jets". Proceedings of the Institution of Civil Engineers - Water Management 160, nr 3 (wrzesień 2007): 169–79. http://dx.doi.org/10.1680/wama.2007.160.3.169.

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21

Richardson, Jerry R., i Kevin York. "Hydrodynamic Countermeasures for Local Pier Scour". Transportation Research Record: Journal of the Transportation Research Board 1690, nr 1 (styczeń 1999): 186–92. http://dx.doi.org/10.3141/1690-21.

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22

Kiraga, Marta J., i Anna Miszkowska. "Lane’s Relation in Local Scour Investigations". IEEE Access 8 (2020): 146967–75. http://dx.doi.org/10.1109/access.2020.3013275.

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23

Nik Hassan, N. M. K., i Rangaswami Narayanan. "Local Scour Downstream of an Apron". Journal of Hydraulic Engineering 111, nr 11 (listopad 1985): 1371–84. http://dx.doi.org/10.1061/(asce)0733-9429(1985)111:11(1371).

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Hoffmans, Gijs J. C. M., i Krystian W. Pilarczyk. "Local Scour Downstream of Hydraulic Structures". Journal of Hydraulic Engineering 121, nr 4 (kwiecień 1995): 326–40. http://dx.doi.org/10.1061/(asce)0733-9429(1995)121:4(326).

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Martin-Vide, J. P., C. Hidalgo i A. Bateman. "Local Scour at Piled Bridge Foundations". Journal of Hydraulic Engineering 124, nr 4 (kwiecień 1998): 439–44. http://dx.doi.org/10.1061/(asce)0733-9429(1998)124:4(439).

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Coleman, Stephen E. "Clearwater Local Scour at Complex Piers". Journal of Hydraulic Engineering 131, nr 4 (kwiecień 2005): 330–34. http://dx.doi.org/10.1061/(asce)0733-9429(2005)131:4(330).

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Sheppard, D. Max, i William Miller. "Live-Bed Local Pier Scour Experiments". Journal of Hydraulic Engineering 132, nr 7 (lipiec 2006): 635–42. http://dx.doi.org/10.1061/(asce)0733-9429(2006)132:7(635).

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Borghei, S. Mahmood, i Aidin Jabbari Sahebari. "Local scour at open-channel junctions". Journal of Hydraulic Research 48, nr 4 (sierpień 2010): 538–42. http://dx.doi.org/10.1080/00221686.2010.492107.

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Barbhuiya, Abdul Karim, i Subhasish Dey. "Local scour at abutments: A review". Sadhana 29, nr 5 (październik 2004): 449–76. http://dx.doi.org/10.1007/bf02703255.

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Annad, Mohamed, i Abdelouahab Lefkir. "New Formula for Calculating Local Scour around Bridge Piers". Advanced Engineering Forum 45 (4.04.2022): 57–64. http://dx.doi.org/10.4028/p-9xgtbb.

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Several researchers working on the axes of solid particle transport, river flow, as well as the vulnerability of structures built on rivers have focused their work on the phenomenon of local scour, where many scour formulas have been proposed. Most of these formulas have been developed using laboratory data, estimated from simplified scaled-down models. This led to uncertainties and considerable inaccuracies in the scour estimation, sometimes causing serious consequences for the stability of structures subject to scour. These formulas were rarely tested using field data, where, until recently, there was very little data to validate them. This study aims to propose a new local scour formula using multiple nonlinear regression (MNLR). The data used is in situ data from an extensive database. The new proposed formula includes different parameters of the three fields involved in the triggering and development of the local scour, namely; the bridge, the flow, and the suspended characteristic of the eroded particle. The results obtained in the training phase and the validation show relatively better performances of the new formula compared to the existing empirical formulas.

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Muhawenimana, Valentine, Nadine Foad, Pablo Ouro i Catherine A. M. E. Wilson. "Local Scour Patterns around a Bridge Pier with Cable-Wrapping". Fluids 8, nr 1 (21.12.2022): 3. http://dx.doi.org/10.3390/fluids8010003.

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The performance of cable flow-altering bed scour countermeasures was experimentally evaluated based on the scour reduction, bed morphology, and the effects on the flow field. An unprotected 40 mm diameter pier was compared to piers protected with spiral cables (2, 4, 6, 8 and 10 mm diameters) wrapped at a 15-degree angle for two-bed sediment sizes with median grain sizes of 0.86 and 1.83 mm, for a cylinder Reynolds number of 7120. The scour depth was reduced by the cables by up to 52 percent compared to the unprotected pier case, a reduction that increased with increasing cable diameter for both sediment beds. Scour depth and sediment deposition varied by sediment size, where the scour hole was up to 45 percent deeper for the finer sediment bed than that of the coarser bed. Velocity and turbulence statistics showed that cables attenuated the flow within the scour hole by diminishing the downflow and horseshoe vortex, whereas in the case of finer sediment, spatially averaged turbulent kinetic energy and Reynolds shear stresses were respectively up to 1.4 and 1.8 times higher for the unprotected pier than the protected pier, resulting in scour depth reduction. The presence of the cable also reduced the vortex shedding frequency in the pier wake as indicated by a Strouhal number of around 0.175. The results demonstrate the potential of cable threading as a flow-altering scour countermeasure to reduce bridge pier scour.

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Wang, Shunyi, Kai Wei, Zhonghui Shen i Qiqi Xiang. "Experimental Investigation of Local Scour Protection for Cylindrical Bridge Piers Using Anti-Scour Collars". Water 11, nr 7 (21.07.2019): 1515. http://dx.doi.org/10.3390/w11071515.

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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.

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Ying, Qiang. "Formula Type of Local Scour Depth on Spur Dike Nose". Applied Mechanics and Materials 641-642 (wrzesień 2014): 271–74. http://dx.doi.org/10.4028/www.scientific.net/amm.641-642.271.

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This passage introduces the formation process of scour hole, analyzes the main factors contributed to the local scour hole’s depth and classifies today’s calculation methods of scour depth into three categories. Then, given the conditions where those methods can be applied and drawbacks of those methods, this article also recommends some suggested formula in calculation.

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Dou, Xiping, Xinzhou Zhang, Xiao-dong Zhao i Xiangming Wang. "LOCAL SCOUR CHARACTERISTICS OF GROINS AT TIDAL WATERWAYS AND THEIR SIMULATION". Coastal Engineering Proceedings 1, nr 32 (31.01.2011): 66. http://dx.doi.org/10.9753/icce.v32.sediment.66.

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For the channel regulation in tidal rivers, groins are often used as typical hydraulic structures. Precisely predicting the local scour depth at the groin head is the key for the project of river regulation. The local scour of groins for tidal rivers is significantly different from that for the undirectional steady flow of general rivers. In the present paper, a three-dimendional (3D) mathematical model for turbulence and sediment transport are establishmented. The local scour near the groin under the actions of tidal current and steady flow are simulated by established 3D turbulence and sediment transport numerical model.The differences of the scour development and the scour pattern near the groin under these two actions are compared.

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Wang, Jun, Zhixing Hou, Hongjian Sun, Bihe Fang, Jueyi Sui i Bryan Karney. "Local scour around a bridge pier under ice-jammed flow condition – an experimental study". Journal of Hydrology and Hydromechanics 69, nr 3 (10.08.2021): 275–87. http://dx.doi.org/10.2478/johh-2021-0014.

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Abstract The appearance of an ice jam in a river crucially distorts local hydrodynamic conditions including water level, flow velocity, riverbed form and local scour processes. Laboratory experiments are used for the first time here to study ice-induced scour processes near a bridge pier. Results show that with an ice sheet cover the scour hole depth around a bridge is increased by about 10% compared to under equivalent open flow conditions. More dramatically, ice-jammed flows induce both greater scour depths and scour variability, with the maximum scour depth under an ice-jammed flow as much as 200% greater than under equivalent open flow conditions. Under an ice-jammed condition, both the maximum depth and length of scour holes around a bridge pier increase with the flow velocity while the maximum scour hole depth increases with ice-jam thickness. Also, quite naturally, the height of the resulting deposition dune downstream of a scour hole responds to flow velocity and ice jam thickness. Using the laboratory data under ice-jammed conditions, predictive relationships are derived between the flow’s Froude number and both the dimensionless maximum scour depth and the dimensionless maximum scour length.

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36

Lantz, Wyatt D., Brian M. Crookston i Michele Palermo. "Evolution of local scour downstream of Type A PK weir in non-cohesive sediments". Journal of Hydrology and Hydromechanics 70, nr 1 (12.02.2022): 103–13. http://dx.doi.org/10.2478/johh-2021-0035.

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Abstract A large-scale piano key weir laboratory study was conducted to investigate the evolution of the scour process occurring in the downstream basin for two non-cohesive granular bed materials, including the analysis of scour-hole geometry and patterns at equilibrium. It was observed that hydraulic conditions, particularly tailwater level, significantly affect the scour mechanisms and equilibrium morphology, eventually resulting in scour depths that exceeded the weir height. Unprecedented insights on the scour dynamics are also provided, along with tools to estimate the time evolution and maximum scour depth, its location in the streamwise direction, and the maximum scour length.

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Liu, Qin, Zhe Wang, Ning Zhang, Hongyu Zhao, Lei Liu, Kunpeng Huang i Xuguang Chen. "Local Scour Mechanism of Offshore Wind Power Pile Foundation Based on CFD-DEM". Journal of Marine Science and Engineering 10, nr 11 (11.11.2022): 1724. http://dx.doi.org/10.3390/jmse10111724.

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The local scour around offshore pile foundations often seriously affects the normal operation of offshore wind power. The most widely used numerical simulation method in the study of local scour is the Euler two-fluid model (TFM). However, the contact effect between sediment particles is neglected in this model. Thus, the momentum and energy transfer between sediment particles and the fluid is not realistically reflected, which limits its significance in revealing the mesoscopic mechanism of local scour. Therefore, the computational fluid dynamics-discrete element method (CFD-DEM) numerical model was applied in this study, which fully considers the contact between solid particles and momentum transfer between two phases. The model was first verified by experimental data of a local scour test under clear water scour. Then, the mechanism of local scour was further discussed from macro and micro perspectives. The results showed that CFD-DEM could be effectively used to study the local scour around a pile foundation. The local scour was comprehensively affected by flow velocity, gravity, fluid force, drag force, and interaction between particles, etc. Although the maximum average drag force happened in the area about 90° from the direction of incoming flow, the maximum scour depth always occurred at about 45°. Corresponding findings and conclusions can be used for future reference when designing and protecting the offshore wind power pile.

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38

Herdiansyah, Sony, Dantje Kardana Natakusumah i Dhemi Harlan. "FVCOM model simulation of local scouring around bridge pile". MATEC Web of Conferences 270 (2019): 04020. http://dx.doi.org/10.1051/matecconf/201927004020.

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Scouring is one of many damages that water can cause. Scouring can occur as a consequence of bridge pile existence. The problem on local scour around single pier will be studied by using FVCOM numerical model. This study objective is to find out how accurate FVCOM model to predict local scour behavior. FVCOM model is based on the finite volume method to solve Navier Stokes, Meyer Peter Muller, and Exner equations. FVCOM computed numerical result then will be verified with computed and measured data in previous numerical (FSUM model) and experimental study. Results from this study show FVCOM model were successfully simulated typical features of local scour around piers such as downflow and wake vortex, but failed to simulate horseshoe vortex. Both computed numerical (FSUM and FVCOM) results are then compared with measured experimental data for its magnitude and time-series of maximum scour depth. FVCOM result shows value 0.99 r-squared correlation and 5.96 percent average error, and FSUM result shows value 0.98 r-squared correlation and 6.82 percent average error. Therefore, it can be deduced that FVCOM successfully predict local scour depth and its time-series and proven that FVCOM is more accurate than FSUM model.

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39

Xiang, Qiqi, Kai Wei, Fang Qiu, Changrong Yao i Yadong Li. "Experimental Study of Local Scour around Caissons under Unidirectional and Tidal Currents". Water 12, nr 3 (27.02.2020): 640. http://dx.doi.org/10.3390/w12030640.

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Local scour around caissons under currents has become one of the main factors affecting the safety of foundation construction and operation in coastal and offshore bridge engineering. Local scour occurs not only in the operation stage, when the caisson has settled into the sediment, but also in the construction stage, when the caisson is suspended in water. In this study, the local scour induced by unidirectional and tidal currents around settled caissons with different cross-sections (circular, square, and diamond) was experimentally investigated. Circular and square caissons were selected to investigate the difference in local scour of suspended caissons under unidirectional and tidal currents. The main findings from the experimental results were: (1) the temporal development of scour under tidal current was slower than that of unidirectional current; (2) the effect of current type can significantly influence the size and location of maximum scour depth around circular and square caissons; (3) the appropriate choice of cross-section could reduce the maximum scour depth around the settled caisson; (4) the maximum scour depth of tidal current was smaller than that of unidirectional current when the caisson was settled into the sediment, while the opposite effect occurred when the caisson was suspended in water.

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40

Liao, Chung-Ta, Keh-Chia Yeh, Yin-Chi Lan, Ren-Kai Jhong i Yafei Jia. "Improving the 2D Numerical Simulations on Local Scour Hole around Spur Dikes". Water 13, nr 11 (23.05.2021): 1462. http://dx.doi.org/10.3390/w13111462.

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Local scour is a common threat to structures such as bridge piers, abutments, and dikes that are constructed on natural rivers. To reduce the risk of foundation failure, the understanding of local scour phenomenon around hydraulic structures is important. The well-predicted scour depth can be used as a reference for structural foundation design and river management. Numerical simulation is relatively efficient at studying these issues. Currently, two-dimensional (2D) mobile-bed models are widely used for river engineering. However, a common 2D model is inadequate for solving the three-dimensional (3D) flow field and local scour phenomenon because of the depth-averaged hypothesis. This causes the predicted scour depth to often be underestimated. In this study, a repose angle formula and bed geometry adjustment mechanism are integrated into a 2D mobile-bed model to improve the numerical simulation of local scour holes around structures. Comparison of the calculated and measured bed variation data reveals that a numerical model involving the improvement technique can predict the geometry of a local scour hole around spur dikes with reasonable accuracy and reliability.

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41

Ahmad, N., T. Mohamed, F. H. Ali i B. Yusuf. "Clear-water local scour at wide piers in shallow-water flow". Water Practice and Technology 9, nr 3 (1.09.2014): 331–43. http://dx.doi.org/10.2166/wpt.2014.035.

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Laboratory data for local scour depth regarding the size of wide piers are presented. Clear water scour tests were performed for various pier widths (0.06, 0.076, 0.102, 0.14 and 0.165 m), two types of pier shapes (circular and rectangular) and two types of uniform cohesionless bed sediment (d50 = 0.23 and d50 = 0.80 mm). New data are presented and used to demonstrate the effects of pier width, pier shape and sediment size on scour depth. The influence of equilibrium time (te) on scouring processes is also discussed. Equilibrium scour depths were found to decrease with increasing values of b/d50. The temporal development of equilibrium local scour depth with new laboratory data is demonstrated for flow intensity V/Vc = 0.95. On the other hand, the results of scour mechanism have shown a significant relationship between normalized volume of scoured and deposited with pier width, b. The experimental data obtained in this study and data available from the literature for wide piers are used to evaluate predictions of existing methods.

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42

Williams, Priscilla, Ram Balachandar i Tirupati Bolisetti. "Examination of Blockage Effects on the Progression of Local Scour around a Circular Cylinder". Water 11, nr 12 (13.12.2019): 2631. http://dx.doi.org/10.3390/w11122631.

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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.

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43

Kawata, Yoshiaki, i Yoshito Ysuchiya. "LOCAL SCOUR AROUND CYLINDRICAL PILES DUE TO WAVES AND CURRENTS COMBINED". Coastal Engineering Proceedings 1, nr 21 (29.01.1988): 97. http://dx.doi.org/10.9753/icce.v21.97.

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Local scour depth around a pile due to waves only is small, but under waves and weak currents combined it became large. If the flow velocity increases, the maximum scour depth increases and may approach to that by running water. In the processes of the scouring, Karman vortex play an important role in deciding characteristics of a scour hole. In the case of the horseshoe vortex predominant, the maximum scour depth is found at the upstream end of a pile, but in the coupled field of waves and currents, the initial scouring position is a little apart from a pile in the offshore side and make an angle of about 45 degree in the shoreward direction. This depends on a vortex shedding from a pile. By using light weight aggregate, the effect of ripples on local scour depth is made clear.

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44

Vuong, Thi-Hong-Nhi, Tso-Ren Wu, Yi-Xuan Huang i Tai-Wen Hsu. "Numerical Analysis of Local Scour of the Offshore Wind Turbines in Taiwan". Journal of Marine Science and Engineering 11, nr 5 (27.04.2023): 936. http://dx.doi.org/10.3390/jmse11050936.

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Rapid expansions of the offshore wind industry have stimulated a renewed interest in the behavior of offshore wind turbines. Monopile, tripod, and jack-up wind turbines support most offshore wind turbines. These foundations are sensitive to scour, reducing their ultimate capacity and altering their dynamic response. However, the existing approaches ignore the seabed’s rheological properties in the scour process. This study focuses on the scour development around the wind turbine foundation in the Changhua wind farm in Taiwan. The simulation results explain the influence of different hydrodynamic mechanisms on the local scours in a cohesive fluid, such as regular waves, random waves, and constant currents. A newly non-Newtonian fluid model, the Discontinuous Bi-viscous Model (DBM), reproduces closet mud material nature without many empirical coefficients and an empirical formula. This new rheology model is integrated and coupled into the Splash3D model, which resolves the Navier–Stokes equations with a PLIC-VOF surface-tracking algorithm. The deformation of the scour hole, the backfilling, and the maximum scour depth are exhibited around the wind turbines. Waves, including regular and irregular waves, do not increase the scour depth compared with currents only. In the case of random wave–current coupling, the results present a signal of scour evolution. However, the scour depth is shallow at 0.033≤S/D≤0.046.

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45

Kadono, Takuma, Sho Kato, Shinichiro Okazaki, Toshinori Matsui, Yoshio Kajitani, Masahide Ishizuka i Hidenori Yoshida. "Effects of Dynamical Change in Water Level on Local Scouring around Bridge Piers Based on In-Situ Experiments". Water 13, nr 21 (27.10.2021): 3015. http://dx.doi.org/10.3390/w13213015.

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To evaluate the stability of bridge piers affected by the local scouring, the existing formulas for estimating the maximum local scour depth have been developed based on the results of experiments conducted under a constant water level. However, the applicability of these formulas to the cases where the water level rises and falls, such as a water level change in a real river, is not clear. In this study, water flow experiments were conducted on cylindrical and oval bridge pier models to investigate the effect of iterated water level change on the progression of local scour around piers. Results of experiments with cylindrical and oval pier showed that the local scour depth and length increased by an iterated action of the water level change; however, these values converged after the number of iterated actions reached a certain time. The local scour length at upstream of the bridge pier was approximately 1.8 times larger than the theoretical value, which was calculated through the local scour depth and angle of repose in water. The local scour length is an important parameter for defining the streambed protection zone, which is one of the measures against local scour, and we showed that the streambed protection zone needs to be defined more widely.

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46

Liang, Bingchen, Shengtao Du, Xinying Pan i Libang Zhang. "Local Scour for Vertical Piles in Steady Currents: Review of Mechanisms, Influencing Factors and Empirical Equations". Journal of Marine Science and Engineering 8, nr 1 (19.12.2019): 4. http://dx.doi.org/10.3390/jmse8010004.

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Scour induced by currents is one of the main causes of the bridge failure in rivers. Fundamental knowledge and mechanisms on scour processes due to currents are often taken as a basis for scour studies, which are the focus of this review. Scour development induced by waves and in combined wave–current conditions are also briefly discussed. For the design of structure foundations, the maximum scour depths need to be estimated. The mechanisms of local scour and predictions of maximum local scour depths have been studied extensively for many years. Despite the complexity of the scour process, a lot of satisfying results and progresses have been achieved by many investigators. In order to get a comprehensive review of local scour for vertical piles, major progresses made by researchers are summarized in this review. In particular, maximum scour depth influencing factors including flow intensity, sediments, pile parameters and time are analyzed with experimental data. A few empirical equations referring to temporary scour depth and maximum scour depth were classified with their expressing forms. Finally, conclusions and future research directions are addressed.

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47

Crowley, Raphael, William Cottrell i Alexander Singleton. "An Examination of the Dependency between Maximum Equilibrium Local Scour Depth and the Grain Size/Structure Size Ratio". Water 12, nr 11 (6.11.2020): 3117. http://dx.doi.org/10.3390/w12113117.

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This paper begins by demonstrating how the Florida Department of Transportation (FDOT) local scour equations take the ratio between grain size and structure size into account when computing equilibrium local scour depth and contrasts this with the well-known Colorado State University (CSU) equation that does not take sediment information into account. Then, a relatively recent empirical formulation from the J-L. Briaud research group for computing local equilibrium scour depth is presented that appears to take the structure size/grain size ratio into account indirectly. Next, a possible explanation for the dependency between local equilibrium scour depth and the structure/grain size ratio is presented that was originally developed by D. Max Sheppard in 2004. This explanation shows that superimposing the pressure gradient around a particle with the pressure gradient around a pile leads to the dependency between equilibrium scour depth and the grain size/structure size ratio. Finally, a new formulation for local equilibrium scour depth based upon turbulent energy spectrum decay is presented. This new formulation reduces the local scour problem to a problem whereby turbulent diffusivity must be better understood. However, this new formulation also appears to show a dependency between equilibrium scour depth and the grain size/structure size ratio. Overall, the analysis presented herein provides several reasons, explanations, and pieces of evidence to suggest that the grain/structure size ratio is an important parameter to consider when computing local equilibrium scour depth.

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Raju, Rahul Dev, Sudhagar Nagarajan, Madasamy Arockiasamy i Stephen Castillo. "Feasibility of Using Green Laser in Monitoring Local Scour around Bridge Pier". Geomatics 2, nr 3 (4.09.2022): 355–69. http://dx.doi.org/10.3390/geomatics2030020.

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Scour around bridge piers is considered as one of the major factors which causes failure of bridges in the United States. An undetected scour can affect the stability of the bridge, eventually leading to the collapse of the bridge. The experimental investigation of scour around a pier using a non-contact measuring method is carried out in this research. A green laser-based non-contact ranging technique is performed on a prefabricated scour hole to study the factors influencing the ability to reconstruct the shape of a scour hole. The experiment was conducted in a 10 ft diameter pool and Leica scan station II was used for the scanning of the scour hole. The turbidity of the water was changed by adding Kaolinite powder to the water. The turbidity was varied from 1.2 NTU to 20.8 NTU by adding Kaolinite. The lab experiments involved changing the turbidity of water to simulate real world conditions. The results from the experimental study show that the turbidity of the water has a direct dependence on the efficiency of the green laser to map the underwater scour profile. The ability of the green laser to capture the fabricated scour hole and pool bed topography were decreased as the turbidity was increased even when the water depth of the pool was reduced. The results from the study show that the green laser is effective in underwater scanning and can be also used for bathymetry profiling and the detection of underwater objects. The method of underwater scanning using a green laser for detecting scour around bridge pier is safe, efficient, and economical.

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Kells, J. A., R. Balachandar i K. P. Hagel. "Effect of grain size on local channel scour below a sluice gate". Canadian Journal of Civil Engineering 28, nr 3 (1.06.2001): 440–51. http://dx.doi.org/10.1139/l01-012.

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In this study, the effect of grain size on the dynamics of local scour processes is discussed in the context of the erosion that takes place downstream from a submerged sluice gate. Four gradations of non-cohesive bed material were used to study the scour process for various tailwater depth and flow rate conditions. The sand gradations included three sizes of uniformly graded sand and a fourth size, which was obtained by mixing the three uniform sands in equal proportions by weight. A total of 36 tests was carried out, each for a period of 24 h. An equilibrium scour condition was not attained over this time period for any of the tests, although a sense of similarity in the bed profiles is observed in the region close to the sluice gate. The present results indicate that the depth and the area of scour are highly dependent on the bed grain size, both increasing as the grain size is reduced. As well, it was found that the tests with a mixed (i.e., graded) sand bed resulted in less scour relative to those in which a uniformly graded sand of similar grain size was used. Moreover, the maximum scour depth increases with increases in the discharge and the tailwater depth. Finally, it was found that the location of the point of maximum scour depth, as measured from the upstream end of the erodible sand bed, moved downstream with an increase in either the discharge or tailwater depth and upstream with an increase in the grain size.Key words: grain size, grain size distribution, local scour, scour dynamics, sluice gate, tailwater depth, video image data acquisition.

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Rasool, Huda, i Thamer A. Mohammed. "Checking the Accuracy of Selected Formulae for both Clear Water and Live Bed Bridge Scour". Journal of Engineering 29, nr 2 (1.02.2023): 99–111. http://dx.doi.org/10.31026/j.eng.2023.02.07.

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Due to severe scouring, many bridges failed worldwide. Therefore, the safety of the existing bridge (after contrition) mainly depends on the continuous monitoring of local scour at the substructure. However, the bridge's safety before construction mainly depends on the consideration of local scour estimation at the bridge substructure. Estimating the local scour at the bridge piers is usually done using the available formulae. Almost all the formulae used in estimating local scour at the bridge piers were derived from laboratory data. It is essential to test the performance of proposed local scour formulae using field data. In this study, the performance of selected bridge scours estimation formulae was validated and statistically tested using field data for existing bridges in Canada, Iraq (Kufa, Najaf), Pakistan, Bangladesh, and India. The validated formulae were HEC-18, Forehlich, and Johnson. The validation was conducted by comparing the predicted local scour depths obtained from applying the above selected formulae with the local scour depths obtained from the field data. The comparison between them was presented using a scattergram. However, statistical tests were used to present the accuracy of the local scour predictions. The tests were conducted using three statistical indices, namely, Theil’s coefficient (U), Mean Absolute Error (MAE), and Root Mean Square Error (RMSE). Among the tested formulae, the Jonson formula gave satisfactory performance since the values of U, MAE, and RMSE were found to be 0.112, 1.351, and 1.650, respectively.

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