Time-Averaged Turbulent Velocity Flow Field through the Various Bridge Contractions during Large Flooding

Yoon, Kwang Seok; Lee, Seung Oh; Hong, Seung Ho

doi:10.3390/w11010143

Cited by 9 publications

(8 citation statements)

References 20 publications

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“…These differences have a direct impact on the scour depth and its temporal evolution and showed that accumulation with larger equivalent roughness height would generate deeper scour. A recent study [31] analyzed the flow dynamic of bridges in pressure-flow conditions, but this study focused on the combined impact of pressure flow and abutment scour, which presents important differences compared to pier scour.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of Flow Structure around Cylindrical Bridge Piers in Pressure-Flow Conditions

Carnacina

Leonardi

Pagliara

2019

Water

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The emerging shift of extreme events, combined with an aging infrastructure and bridges, highlights the potential increase in the risk of damage and catastrophic failure of bridges with climate change. This article analyzes the behavior of the flow and turbulence features in proximity to bridge piers, at two different moments of the scour temporal evolution in free-surface and pressure-flow conditions. Bridge pressure-flow conditions occur when the water depth submerges a bridge deck during extreme events. A circular pier and two rectangular decks of different lengths were used for this research. All tests were carried out in clear water conditions at the sediment critical velocity. This paper studied first the rate of scour temporal evolution and scour morphologies. Second, velocity measurements were taken using a Nortek acoustic Velocimeter at 25 Hz sampling rate in both free-surface and pressure-flow conditions. The average three-dimensional flow velocities, turbulence intensities, Reynolds stress, and turbulent kinetic energy were studies for the cross section corresponding to the center of the pier. The results show that pressure flow conditions accelerate the scour rate. This rate approximately reaches twice the scour in free-surface conditions with a vertical contraction of about 17%. Flow and turbulence measurements clearly exhibit how, under pressure-flow conditions, the additional turbulence and accelerated velocity modifies the flow pattern and circulation, accelerating the scour evolution around the bridge base. While numerous studies exist for pier scour and turbulence in free-surface conditions, pressure flow conditions received limited attention in the past. These results provide essential information for understanding scour mechanisms and for facilitating the design of future structures to increase bridge safety and resilience.

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Section: Introductionmentioning

confidence: 99%

Characteristics of Flow Structure around Cylindrical Bridge Piers in Pressure-Flow Conditions

Carnacina

Leonardi

Pagliara

2019

Water

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“…The approach section of the pier model was 15.0 m long followed by a working mobile bed section with a length of 3.0 m in which the pier model was placed. The length of the approach section was decided based on the findings from other researches [25][26][27][28][29] to ensure a fully developed approach turbulent flow and turbulent boundary layer at the bridge pier. After the working mobile bed section, additional 3 m long sediment trap section downstream of the pier model was placed.…”

Section: Methodsmentioning

confidence: 99%

Turbulence Characteristics before and after Scour Upstream of a Scaled-Down Bridge Pier Model

Lee

Hong

2019

Water

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Bridge pier scour is one of the main causes of bridge failure and a major factor that contributes to the total construction and maintenance costs of bridge. Recently, because of unexpected high water during extreme hydrologic events, the resilience and security of hydraulic infrastructure with respect to the scour protection measure along a river reach has become a more immediate topic for river engineering society. Although numerous studies have been conducted to suggest pier scour estimation formulas, understanding of turbulence characteristics which is dominant driver of sediment transport around a pier foundation is still questionable. Thus, to understand near bed turbulence characteristics and resulting sediment transport around a pier, hydraulic laboratory experiments were conducted in a prismatic rectangular flume using scale-down bridge pier models. Three-dimensional velocities and turbulent intensities before and after scour were measured with Acoustic Doppler Velocimeter (ADV), and the results were compared/analyzed using the best available tools and current knowledge gained from recent studies. The results show that the mean flow variable is not enough to explain complex turbulent flow field around the pier leading to the maximum scour because of unsteady flows. Furthermore, results of quadrant analysis of velocity measurements just upstream of the pier in the horseshoe vortex region show significant differences before and after scour.

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“…The simultaneous influence of such processes as the unsustainable movement of water medium and river structures; the existence of significant areas with turns; re-formation of watercourse and floodplain shape in the process of deformation leads to the development of general and local washouts in the area of influence of bridge crossings. In order to study the devastating effects of natural floods as consequences of climate change, paper [2] represents laboratory research into a physical model -the area of river flow with a bridge crossing. Based on the conducted studies, it was concluded on the significant influence of a bridge crossing due to blocking the floodplain flow, corresponding re-formation and an increase in velocities, increased intensity of sediment transfer in the watercourse, at the same time, deformation processes on floodplains were not considered.…”

Section: Literature Review and Problem Statementmentioning

confidence: 99%

“…In the expanded form equation 1and (2) are written down as follows: 2 3 3 1 3 2 3 1 2 3 2 3 1 3 2 3 3 3 1 2 3 1 ,…”

Section: The Aim and Objectives Of The Studymentioning

confidence: 99%

“…S z However, the magnitude ( ) S z must be added from the rationally constructed theory of motion of drawn alluvium, but such a theory does not exist. A certain step in the elimination of the above drawback of the existing theories of bottom sediments is made in the procedure explored in paper [2], containing the dependences for determining specific discharge of suspended sediments. Such dependence where S 0 is the countdown concentration of bottom sediments determined using the procedure [2]; F is the factor that takes into account the parameter of alluvium suspension, determined using the procedure [2].…”

Section: Development Of a Mathematical Model Of A Floodplain Flow mentioning

confidence: 99%

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Predicting deformations in the area of impact exerted by a bridge crossing based on the proposed mathematical model of a floodplain flow

Slavinska

Tsynka²,

Bashkevych

2020

EEJET

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To develop the methods for predicting deformations on floodplain areas in the zone of influence of bridge crossings, a mathematical model of a suspended flow with grass vegetation was developed. The problem of calculating the hydrodynamic fields of velocities and pressure in artificially compressed flows refers to the theory of shallow water since the vertical size (flow depth) is substantially smaller than the horizontal dimensions, such as length and width. In accordance with this, the proposed model is based on the equation of distribution of velocity structure and the depth of a floodplain flow in approximation to two-dimensional dependences taking into consideration force factors. Force factors determine resistance at flowing around vegetation in floodplain areas and resistance of washout of fine-grained soil. To obtain an unambiguous solution of the considered problem, boundary and initial conditions were added to the presented closed system of original equations. These conditions make it possible to determine the level of a free surface of flow and the zone of influence of a bridge crossing at different stages of the estimated flood. Based on finite-difference analogs of transfer equations, the distribution of velocities and depths in estimated sections was calculated. By iteration, the longitudinal velocity in a flood flow with vegetation elements was determined. The results of the calculation of washout on floodplain areas of a sub-bridge watercourse of the lowland river Siversky Donets were obtained. The depth of a flood flow after a washout was determined based on the ratios of actual and flood-free velocities. When compared with the initial bottom marks, the washout of the larger floodplain is 0.96 m, that of the smaller floodplain-1.28 m. The proposed scientifically substantiated solution for ensuring optimum interaction of floodplain flows with bridge crossings makes a certain contribution to improving the reliability of their operation due to the quality of design works and the corresponding reduction of construction and operating costs

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Time-Averaged Turbulent Velocity Flow Field through the Various Bridge Contractions during Large Flooding

Cited by 9 publications

References 20 publications

Characteristics of Flow Structure around Cylindrical Bridge Piers in Pressure-Flow Conditions

Characteristics of Flow Structure around Cylindrical Bridge Piers in Pressure-Flow Conditions

Turbulence Characteristics before and after Scour Upstream of a Scaled-Down Bridge Pier Model

Predicting deformations in the area of impact exerted by a bridge crossing based on the proposed mathematical model of a floodplain flow

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