Large-eddy simulation of the Mississippi River under base-flow condition: hydrodynamics of a natural diffluence-confluence region

Le, Trung Bao; Khosronejad, Ali; Sotiropoulos, Fotis; Bartelt, Nicole; Woldeamlak, Solomon; DeWall, Petronella

doi:10.1080/00221686.2018.1534282

Cited by 34 publications

(23 citation statements)

References 56 publications

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“…It is worth mentioning that the modeling accuracy for flow velocity may not be further improved by using more advanced CFD modeling or more refined mesh without improving the accuracy of ADCP and topography survey. For instance, Le et al (2019) conducted a large-eddy-simulation for a 3.2 km long reach of the Mississippi River with a given discharge, the prediction accuracy of velocity was not improved when compared to ADCP measurements even though using 109 million grid and 38,400 CPU hours to reach a steady state. Furthermore, as the two dates chosen for velocity validation are randomly selected, it may be reasonable to expect that flow velocity modeling at other dates likely has similar accuracy, at least for short-term scenarios.…”

Section: Short-term Velocity Validationmentioning

confidence: 99%

“…In addition, it is observed that the distribution is "cleaner" in CFD data (e.g., x), but shows more noise in ADCP measurements (e.g., w). Such a noise feature is likely induced by small scale turbulence, measurement uncertainty from boat movement (Khosronejad et al, 2016;Le et al, 2019), 1b, the first character in "Time Period" represents short-term (S), medium-term (M), and long-term (L), and the second character in "Time period" represents medium (M), high (H), low (L), or mixed (M) type flow scenarios. Superscripts 2 and 3 denote observation data used for comparison are from observation 2 and observation 3.…”

Section: Short-term Velocity Validationmentioning

confidence: 99%

“…All 3D models mentioned above adopted the Reynolds-averaged Navier-Stokes concept. More advanced models such as large-eddy-simulation have also been applied for natural streams by using high-performance computers and airborne Light Detection and Ranging (LiDAR) measured high-resolution topography (Khosronejad et al, 2016;Le et al, 2019;Khosronejad et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

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Modeling of streamflow in a 30-kilometer-long reach spanning 5 years using OpenFOAM 5.x

Chen

Bao

Fang

et al. 2021

Preprint

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Abstract. Developing accurate and efficient modeling techniques for streamflow at tens-kilometer spatial scale and multi-year temporal scale is critical for evaluating and predicting the impact of climate- and human-induced discharge variations on river hydrodynamics. However, achieving such a goal is challenging because of limited surveys of streambed hydraulic roughness, uncertain boundary condition specifications, and high computational costs. We demonstrate that accurate and efficient three-dimensional (3D) hydrodynamic modeling of natural rivers at 30-kilometer and 5-year scales is feasible using the following three techniques within OpenFOAM, an open source computational fluid dynamics platform: 1) generating a distributed hydraulic roughness field for the streambed by integrating water stage observation data, a rough wall theory, and a local roughness optimization and adjustment strategy; 2) prescribing the boundary condition for the inflow and outflow by integrating pre-computed results of a one-dimensional (1D) hydraulic model with the 3D model; and 3) reducing computational time using multiple parallel runs constrained by 1D inflow and outflow boundary conditions. Streamflow modeling for a 30-kilometer-long reach in the Columbia River (CR) over 58 months can be achieved in less than six days using 1.1 million CPU hours. The mean error between the modeled and the observed water stages for our simulated CR reach ranges from −16 cm to 9 cm (equivalent to ca. ±7 % relative to the average water depth) at seven locations during most of the years between 2011 and 2019. We can reproduce the velocity distribution measured by the acoustic Doppler current profiler (ADCP). The correlation coefficients of the depth-averaged velocity between the model and ADCP measurements are in the range between 0.71 and 0.83 at 75 % of the survey cross-sections. With the validated model, we further show that the relative importance of dynamic pressure versus hydrostatic pressure varies with discharge variations and topography heterogeneity. Given the model's high accuracy and computational efficiency, the model framework provides a generic approach to evaluate and predict the impact of climate- and human-induced discharge variations on river hydrodynamics at tens kilometer and decade scales.

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Section: Short-term Velocity Validationmentioning

confidence: 99%

Section: Short-term Velocity Validationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Modeling of streamflow in a 30-kilometer-long reach spanning 5 years using OpenFOAM 5.x

Chen

Bao

Fang

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…Usually, the branches are relatively stable in bedform. The differences in geometry within the unit generate complex flow patterns at each end (Le et al, 2018). With economic development, the river morphological changes and riverine human activities affect each other; their relationship is reciprocal.…”

Section: Introductionmentioning

confidence: 99%

“…The diffluence‐confluence unit is a key geo‐morphological element and exhibits a coupled behaviour of flow and sediment in between. Many studies focus mostly on separate examinations of diffluence or confluence; more attention should be paid to their interplay (Hackney et al, 2018; Le et al, 2018). Within the unit, the adjustment of flow, sediment and morphology goes reciprocal with changes in flow discharge.…”

Section: Introductionmentioning

confidence: 99%

Flow and sediment behaviours and morpho‐dynamics of a diffluence−Confluence unit

Xie

Yang

Lundström

2020

River Research & Apps

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A diffluence-confluence unit is an elementary component within a river system and presents a complex yet linked pattern of both flow and sediment transport in between. This study deals, by means of field investigations and numerical modelling, with morpho-dynamics of such a unit on the lower Yangtze River reaches. The unit comprises, looking downstream, a secondary (left) course and a main (right) course. Field surveys are performed for measurements of flow discharge, sediment loads at selected locations and river bathymetry at certain intervals. The field data show that

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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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Large-eddy simulation of the Mississippi River under base-flow condition: hydrodynamics of a natural diffluence-confluence region

Cited by 34 publications

References 56 publications

Modeling of streamflow in a 30-kilometer-long reach spanning 5 years using OpenFOAM 5.x

Modeling of streamflow in a 30-kilometer-long reach spanning 5 years using OpenFOAM 5.x

Flow and sediment behaviours and morpho‐dynamics of a diffluence−Confluence unit

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

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