Comparative Hydrodynamic Study of Rigid-Lid and Level-Set Methods for LES of Open-Channel Flow

Khosronejad, Ali; Arabi, Mahsa Ghazian; Angelidis, Dionysios; Bagherizadeh, Elaheh; Flora, Kevin; Farhadzadeh, Ali

doi:10.1061/(asce)hy.1943-7900.0001546

Cited by 26 publications

(15 citation statements)

References 29 publications

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“…Also, our confluence is absent of abutments or obstructions that can cause local transitions from subcritical to supercritical flow. Such transitions can lead to incorrect predictions of turbulent statistics when modelled using a rigid-lid assumption (Khosronejad et al, 2019). Additional research on free-surface treatment of full-scale mesoscale confluence models is necessary to further understand the potential drawbacks of the rigid-lid assumption.…”

Section: Wall-modelled Large-eddy Simulationmentioning

confidence: 99%

Large‐scale turbulent mixing at a mesoscale confluence assessed through drone imagery and eddy‐resolved modelling

Duguay

Biron

Bélanger

2021

Earth Surf Processes Landf

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Confluences are sites of intense turbulent mixing in fluvial systems. The large-scale turbulent structures largely responsible for this mixing have been proposed to fall into three main classes: vertically orientated (Kelvin-Helmholtz) vortices, secondary flow helical cells and smaller, strongly coherent streamwise-orientated vortices. Little is known concerning the prevalence and causal mechanisms of each class, their interactions with one another and their respective contributions to mixing. Historically, mixing processes have largely been interpreted through statistical moments derived from sparse pointwise flow field and passive scalar transport measurements, causing the contribution of the instantaneous flow field to be largely overlooked. To overcome the limited spatiotemporal resolution of traditional methods, herein we analyse aerial video of large-scale turbulent structures made visible by turbidity gradients present along the mixing interface of a mesoscale confluence and complement our findings with eddy-resolved numerical modelling. The fast, shallow main channel (Mitis) separates over the crest of the scour hole's avalanche face prior to colliding with the slow, deep tributary (Neigette), resulting in a streamwise-orientated separation cell in the lee of the avalanche face. Nascent large-scale Kelvin-Helmholtz instabilities form along the collision zone and expand as the high-momentum, separated near-surface flow of the Mitis pushes into them. Simultaneously, the strong downwelling of the Mitis is accompanied by strong upwelling of the Neigette. The upwelling Neigette results in $50% of the Neigette's discharge crossing the mixing interface over the short collision zone. Helical cells were not observed at the confluence. However, the downwelling Mitis, upwelling Neigette and separation cell interact to generate considerable streamwise vorticity on the Mitis side of the mixing interface. This streamwise vorticity is strongly coupled to the large-scale Kelvin-Helmholtz instabilities, which greatly enhances mixing. Comparably complex interactions between large-scale Kelvin-Helmholtz instabilities and coherent streamwise vortices are expected at other typical asymmetric confluences exhibiting a pronounced scour hole.

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Section: Wall-modelled Large-eddy Simulationmentioning

confidence: 99%

Large‐scale turbulent mixing at a mesoscale confluence assessed through drone imagery and eddy‐resolved modelling

Duguay

Biron

Bélanger

2021

Earth Surf Processes Landf

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“…Chou and Fringer [45] studied the sediment suspension using Large Eddy Simulation with a dynamic mixed model. Khosronejad et al [46,47] studied the rigid lid and level set methods for LES of openchannel flow. McCoy et al [48,49] used LES to study the flow hydrodynamics in a groin field and found that most of the fluid leaves the embayment via the top layer of the channelembayment interface (upstream half) and enters the embayment at levels situated around the mid-depth.…”

Section: Introductionmentioning

confidence: 99%

Modeling Local Scour around a Cylindrical Pier with Circular Collar with Tilt Angles (Counterclockwise around the Direction of the Channel Cross-Section) in Clear-Water

Tian

Zhang

2021

Water

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This research explores how a circular collar with a tilt angle (counterclockwise around the direction of the channel cross-section) could affect the local scour depth around a single cylindrical pier in clear-water based on Large Eddy Simulation (LES) in six cases. The results show that a horizontal circular collar is the best for reducing the local scour depth. With the increases of the tilt angle, the effect on reducing the local scour depth decreases gradually and is even counterproductive at the scour equilibrium. At the early stage of scouring, cases with circular collars show obvious scouring depth reductions. The smaller the tilt angle is, the better and longer-lasting the protection that the circular collar can provide. When the tilt angle is smaller than 5°, the location of the maximum local scouring is around 90–115° (the angle is measured clockwise from the flow direction) on both sides of the pier. When the tilt angle is greater than 5°, the depth of local scouring in the range around −115° to 115° is close to the maximum local scouring depth. Significantly larger areas reach the maximum scouring depth when the tilt angle increases. Compared to Case 1 (the pier without a circular collar), in the cases with a circular collar, the topographies downwards the pier in 1.0D (D is the diameter of the bridge pier) are changed to siltation from scouring. The topography downwards the pier changes from scouring to siltation with the increase of the tilt angle, and the shape of siltation changes from a long-narrow rectangle to an equilateral triangle. This study may provide valuable insights into the protection of the local scour of the pier.

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“…Indeed, one of the most complex challenges in hydraulics and environmental turbulent flows, the multi-phase flow simulation using interfacecapturing schemes, is amenable to study by LES [16,17,18]. In free-surface open-channel flows, adopting the Level-Set Method (LSM) to represent the air-water interface can provide more accurate results than using the classic frictionless rigid-lid boundary condition, but the former comes at five times higher computational expense (Krosronejad et al [19]).…”

Section: Introductionmentioning

confidence: 99%

On the performance of a highly-scalable Computational Fluid Dynamics code on AMD, ARM and Intel processors

Ouro,

Lopez-Novoa,

Guest

2020

Preprint

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No area of computing is hungrier for performance than High Performance Computing (HPC), the demands of which continue to be a major driver for processor performance and adoption of accelerators, and also advances in memory, storage, and networking technologies. A key feature of the Intel processor domination of the past decade has been the extensive adoption of GPUs as coprocessors, whilst more recent developments have seen the increased availability of a number of CPU processors, including the novel ARM-based chips. This paper analyses the performance and scalability of a state-of-the-art Computational Fluid Dynamics (CFD) code on three HPC cluster systems equipped with AMD EPYC-Rome (EPYC, 4096 cores), ARM-based Marvell ThunderX2 (TX2, 8192 cores) and Intel Skylake (SKL, 8000 cores) processors. Three benchmark cases are designed with increasing computation-to-communication ratio and numerical complexity, namely lid-driven cavity flow, Taylor-Green vortex and a travelling solitary wave using the level-set method, adopted with 4 th -order central-differences or a 5 th -order WENO scheme. Our results show that the EPYC cluster de-

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Comparative Hydrodynamic Study of Rigid-Lid and Level-Set Methods for LES of Open-Channel Flow

Cited by 26 publications

References 29 publications

Large‐scale turbulent mixing at a mesoscale confluence assessed through drone imagery and eddy‐resolved modelling

Large‐scale turbulent mixing at a mesoscale confluence assessed through drone imagery and eddy‐resolved modelling

Modeling Local Scour around a Cylindrical Pier with Circular Collar with Tilt Angles (Counterclockwise around the Direction of the Channel Cross-Section) in Clear-Water

On the performance of a highly-scalable Computational Fluid Dynamics code on AMD, ARM and Intel processors

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