Influence of turbulent horseshoe vortex and associated bed shear stress on sediment transport in front of a cylinder

Li, Jinzhao; Mo, Qi; Fuhrman, David R.; Chen, Qigang

doi:10.1016/j.expthermflusci.2018.05.008

Cited by 28 publications

(23 citation statements)

References 51 publications

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“…Laws for flow field around the pile, including velocity and pressure distributions in three dimensions, characteristics of horseshoe vortex and vortices shedding, boundary layer and shear stress near the bed were successfully obtained by scholars [6,10,17,21,23]. The transportation of a single sediment particle was traced in detail [30,32,33], which contributed to the calculation of the sediment transport rate.…”

Section: Introductionmentioning

confidence: 99%

“…With the Kolmogorov's theory of turbulence [19,20], Manes and Brocchini [16] derived the interactions between large-scale and small-scale eddies impinging the scour hole surface. More recently, Li et al [21] used a 2D PIV system to study the relationships between turbulence horseshoe vortex and shear Large amounts of studies have been conducted to study the local scour regime [3][4][5][6][7][8][9]. By using an acoustic Doppler velocity meter (Micro-ADV) in three-dimensional analysis of bursting process, for instance, Keshavarzi et al [7] predicted the transition probabilities, occurrence probabilities and directions of sediment particles movements.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Local Scour for Vertical Piles in Steady Currents: Review of Mechanisms, Influencing Factors and Empirical Equations

Liang

Pan

et al. 2019

JMSE

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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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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Local Scour for Vertical Piles in Steady Currents: Review of Mechanisms, Influencing Factors and Empirical Equations

Liang

Pan

et al. 2019

JMSE

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“…Particularly, the RSNs in the last vegetation section were 2.5 times larger than that of the non-vegetation section, which may be caused by the horseshoe vortex [59] and the karman vortex [60] generated by the impediment of the vegetation stem. The presence of these vortices would successively cause the rise of turbulent kinetic energy [61]. Figure 10b exhibited the vertical depth distribution of RSN in different directions of LS1 at the last cross section of SMD arrangement, which basically changed in a consistent manner: as the water depth increased, the RSN initially increased and then decreased.…”

Section: Reynolds Stress Numbermentioning

confidence: 94%

Experimental Study of Overland Flow through Rigid Emergent Vegetation with Different Densities and Location Arrangements

Wang

Zhang

Yang

et al. 2018

Water

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The effect of vegetation density on overland flow dynamics has been extensively studied, yet fewer investigations have focused on vegetation arrangements with different densities and position features. Flume experiments were conducted to investigate the hydrodynamics of flow through rigid emergent vegetation arranged in combinations with three densities (Dense, Middle, and Sparse) and three positions (summit, backslope, and footslope). This study focused on how spatial variations regulated hydrodynamic parameters from two dimensions: direction along the slope and water depth. The total hydrodynamic parameters of bare slopes were significantly different from those of vegetated slopes. The relationship between Re and f illustrated that Re was not a unique predictor of hydraulic roughness on vegetated slopes. In the slope direction, all hydrodynamic parameters on vegetated slopes exhibited fluctuating downward/upward trends due to the clocking effect before the vegetated area and the rapid conveyance effect in the vegetated area, whereas constant values were observed on bare slopes. The performance of hydrodynamics parameters suggested that the dense rearward arrangement (SMD) was the optimal vegetation pattern to regulate flow conditions. Specifically, the vertical profiles of the velocity and turbulence features of the SMD arrangement at different sections demonstrated the significant role of vegetation density in identifying the velocity layers along the water depth. The maximum velocity and Reynolds Stress Number (RSN) indicated the position where local scour was most likely to occur, which would improve our basic understanding of the mechanisms underlying hydraulic and soil erosion processes.Thus, determining the optimum conditions for flow within vegetated slopes is vital for water and soil conservation and control.To understand the mechanisms underlying the hydraulic and soil erosion processes on vegetated hillslopes, hydrodynamic characteristics, which were mainly quantified by hydraulic parameters, e.g., water depth, mean velocity, flow pattern and resistance, kinetic energy and momentum distributions were considered as fundamental variables [6,7]. The hydrodynamic effects of emergent vegetation have been widely investigated in controlled laboratory experiments. In previous studies, well-defined rigid cylinder rods were assumed to represent an appropriate model for groups and trees or reeds and to generate accurate representations of the geometric characteristics [8]; thus, this method has been utilized as vegetation stems in numerous laboratory studies [7]. Generally, vegetation promotes the water depth [9], slows down the flow [10,11], enhances flow resistance [12], raises energy and momentum coefficients [13], attenuates the turbulence intensity [14], and promotes diffusion and deposition processes [15]. Dunkerley et al. [16] pointed out that plants could stabilize the flow state as laminar flow, whereas Hamilton et al. [17] stated that mixed flow states occurred on vegetated slopes. The definition of t...

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“…Sumer and Fredsøe [23] observed that the maximum bed shear stress appeared at the midway from the front to the side edge of a pier, which was at least five times higher than that for the undisturbed approach flow. Likewise, Li et al [24] experimentally measured the flow characteristics in front of a cylinder, showing that both the mean and fluctuations of bed shear stress are significantly augmented due to the formation of turbulent horseshoe vortex. The large amplification of the turbulence intensity and bed shear stress, which greatly enhances the flow capability to entrain and transport sediment particles [19], substantiates the central role of the horseshoe vortex system in initiating the local scour and thus generates the potential maximum scour depth.…”

Section: Characteristics Of Horseshoe Vortexmentioning

confidence: 96%

Scaling of Scour Depth at Bridge Pier Based on Characteristic Dimension of Large-Scale Vortex

Cheng

Wei

2019

Water

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By examining the variations in the dimensions of a horseshoe vortex system in front of a pier, the present study proposes a new length scale, called pier hydraulic radius, for the scaling of the maximum scour depth at a bridge pier. It is shown that, in comparison with other length scales, the pier hydraulic radius is more effective for quantifying combined effects of pier width and flow depth on the local scour for both low and high flow conditions. A theoretical formula is finally derived, which agrees well with experimental data reported in the literature.

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Influence of turbulent horseshoe vortex and associated bed shear stress on sediment transport in front of a cylinder

Cited by 28 publications

References 51 publications

Local Scour for Vertical Piles in Steady Currents: Review of Mechanisms, Influencing Factors and Empirical Equations

Local Scour for Vertical Piles in Steady Currents: Review of Mechanisms, Influencing Factors and Empirical Equations

Experimental Study of Overland Flow through Rigid Emergent Vegetation with Different Densities and Location Arrangements

Scaling of Scour Depth at Bridge Pier Based on Characteristic Dimension of Large-Scale Vortex

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