Discussion of “Coherent Structures in the Flow Field around a Circular Cylinder with Scour Hole” by G. Kirkil, S. G. Constaninescu, and R. Ettema

Gobert, Christian; Link, Óscar; Manhart, Michael; Zanke, Ulrich

doi:10.1061/(asce)hy.1943-7900.0000032

Cited by 15 publications

(6 citation statements)

References 2 publications

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“…This region upstream of the horseshoe vortex is described by Melville (1975) as "dead", while Kirkil et al (2008Kirkil et al ( , (2009 observed a stationary vortex attached to the scour surface next to a secondary horseshoe vortex. Additionally, vortices are randomly shed from the scour rim interacting with the secondary horseshoe vortex (Gobert et al 2009). Melville and Raudkivi (1977) identified the streamwise turbulence intensity √ u �2 ∕u b to be largest in the intermediate state of the scour development.…”

Section: Introductionmentioning

confidence: 99%

Flow around a scoured bridge pier: a stereoscopic PIV analysis

Jenssen

Manhart

2020

Exp Fluids

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We performed stereoscopic particle image velocimetry of the turbulent flow inside a scour hole around a cylinder in a sandy bed. At two planes, symmetry plane and $$45^\circ$$ 45 ∘ with respect to the approach flow, the flow and its turbulence structure were investigated. We used two Reynolds numbers (20, 000 and 39, 000) based on the cylinder diameter and the depth-averaged velocity in the symmetry plane. The flow is characterized by a strong down-flow in front of the cylinder, a large horseshoe vortex inside the scour, and an upstream directed wall jet underneath. The values of vorticity in the horseshoe vortex and of the velocity in the wall jet are larger than in a comparable configuration on a flat bed. Enhanced levels of turbulent kinetic energy are found around the horseshoe vortex and in the shear layer detaching from the rim. The orientation of the main axis of the velocity fluctuations changes when the flow enters the scour hole: from about wall-parallel in the detaching shear layer to vertical at the horseshoe vortex. The production of turbulent kinetic energy shows a maximum upstream of the horseshoe vortex centre with considerable production in the shear layer and in the wall jet underneath the horseshoe vortex. Furthermore, strong wall-parallel velocity fluctuations are visible in this region, and bimodal velocity distributions are found, but not anywhere else. The time-averaged wall-shear stresses are largest under the horseshoe vortex and most likely larger than in a corresponding flat-bed configuration. Graphic abstract

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Section: Introductionmentioning

confidence: 99%

Flow around a scoured bridge pier: a stereoscopic PIV analysis

Jenssen

Manhart

2020

Exp Fluids

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“…) and of time-dependent maximum scour depth (Dey, 1999;Melville and Chiew, 1999;Mia and Nago, 2003;Oliveto and Hager, 2002;Yanmaz and Altinbilek, 1991;Zanke, 1982). Others concentrated on the flow field around the cylinder, via experimental measurements (Dey and Raikar, 2007;Graf and Istiarto, 2002;Graf and Yulistiyanto, 1998;Unger and Hager, 2007) and numerical experiments (Gobert et al, 2010;Kirkil et al, 2008Kirkil et al, , 2009Rolound et al, 2005). Link et al (2008) and Diab et al (2010) presented detailed measurements of developing and equilibrium scour holes around cylinders in fine sand and gravel, respectively.…”

Section: Introductionmentioning

confidence: 99%

Equilibrium scour depths around piles in noncohesive sediments under currents and waves

Zanke

Hsu

Roland

et al. 2011

Coastal Engineering

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“…The researchers in [45] conducted an experimental study of clear water scouring around a circular cylinder, identifying the HSV as the main scour mechanism, due to the enhanced bed shear stress under the horseshoe vortices. The authors in [46] used numerical simulations of the flow field in the scour hole around a cylinder to show the importance of side slides in the scouring process. The study in [47] showed differences in the scour mechanism, depending on the flow intensity (I), i.e., the ratio between the flow velocity and the critical velocity for the incipient motion of sediment particles.…”

Section: Subcritical Flowsmentioning

confidence: 99%

Scour at Bridge Foundations in Supercritical Flows: An Analysis of Knowledge Gaps

Link

Mignot

Roux³

et al. 2019

Water

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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.Large-scale supercritical free-surface flows can occur in different environments. Some examples can be found in cases of flooded urban streets, fish-ways, tsunami inland flows, coastal channels, and mountain rivers. This paper focuses on the flow and scouring patterns at bridge foundations in rivers with supercritical conditions. The occurrence of supercritical flows in rivers is defined by high longitudinal slopes (>1%) and/or rapid flood waves. Commonly, steep rivers present gravel beds or mixtures of fine and coarse sediments, containing all possible sizes, from clay and silt up to boulders tens of centimeters in size. In dentritic networks, streams with a low Strahler's order (i.e., <3) are steep and produce flash floods but normally possess a small cross-sectional width. Therefore, deck bridges without foundations in these riverbeds are usually selected. At piedmont, however, rivers widen and it is common to observe cross sections with widths over 50 m, where bridge foundations may have to be included. Salient examples of such configurations are often encountered in steep watersheds subjected to heavy rains, such as on the Panamericana Route along Perú and Chile, La Réunion Island (Indian Ocean) in Taiwan or Japan, and also in a few European Alpine piedmont rivers (Figure 1). The examples in Figure 1 clearly highlight that supercritical flows are associated with a significant amount of energy for scouring and dynamic loading of the superstructure. Wood debris can also enhance the risk of pier stability. Such flows thus produce among the worst hydraulic conditions for bridge design. A recent bridge collapse due to scour in a supercritical flow occurred at the Rivière Saint Etienne in the La Réunion island due to cyclone Gamède. This bridge, which connected a road with traffic of 65,000 vehicles per day, collapsed and modified the terrestrial transport route for a long time (Figure 1f,g), thereby producing large economic losses. This event motivated, i...

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Discussion of “Coherent Structures in the Flow Field around a Circular Cylinder with Scour Hole” by G. Kirkil, S. G. Constaninescu, and R. Ettema

Cited by 15 publications

References 2 publications

Flow around a scoured bridge pier: a stereoscopic PIV analysis

Flow around a scoured bridge pier: a stereoscopic PIV analysis

Equilibrium scour depths around piles in noncohesive sediments under currents and waves

Scour at Bridge Foundations in Supercritical Flows: An Analysis of Knowledge Gaps

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