Shallow flow past a cavity: globally coupled oscillations as a function of depth

Tuna, Burak A.; Tinar, E.; Rockwell, D.

doi:10.1007/s00348-013-1586-3

Cited by 31 publications

(65 citation statements)

References 27 publications

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“…Tuna et al. () stated that the turbulence vortices created by the corners of the cavities excite the flow, leading to regular pulses in the flow. The phenomenon extended to the middle of the channel, where a small oscillation was observed (1–3 mm, depending on the configuration).…”

Section: Resultsmentioning

confidence: 89%

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Transport of suspended sediments under the influence of bank macro‐roughness

Juez

Bühlmann

Maechler

et al. 2017

Earth Surf Processes Landf

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River restoration works often include measures to promote morphological diversity and enhance habitat suitability. One of these measures is the creation of macro-roughness elements, such as lateral cavities and embayments, in the banks of channelized rivers. However, in flows that are heavily charged with fine sediments in suspension, such as glacier-fed streams and very low-gradient reaches of large catchment rivers, these lateral cavities may trap these sediments. Consequently, the morphological changes may be affected, and the functionality of the restoration interventions may be compromised. Herein, we analyse the influence of these macro-roughness elements on the transport of fine sediments in the main channel. Laboratory tests with uniform flow charged with sediments in a channel with banks equipped with large-scale rectangular roughness elements were carried out. The laboratory experiments covered a wide range of rectangular cavity geometrical configurations and shallowness ratios. The influence of key parameters such as flow shallowness, geometric ratios of the cavities and initial sediment concentration was tested. Surface particle image velocimetry, sediment samples and temporal turbidity records were collected during the experiments. The amount of sediments captured by the cavities, the temporal evolution of the concentration of sediments in suspension and the flow hydrodynamics are cross-analysed and discussed. It is shown that the trapping efficiency of the macro-roughness elements is a clear function of the channel geometry and the shallowness of the flow.

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Section: Resultsmentioning

confidence: 89%

“…Recent studies (Tuna et al. ; Akutina, ) theorize that these secondary eddies drag the sediments towards the centre of the vortex, where they subsequently settle down. The findings herein provided confirm this theory.…”

Section: Discussionmentioning

confidence: 99%

Transport of suspended sediments under the influence of bank macro‐roughness

Juez

Bühlmann

Maechler

et al. 2017

Earth Surf Processes Landf

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“…O'Connor et al () expressed the linear single transient storage model (STSM) for SSZs as follows:

\frac{normald C}{normald t} = - \frac{E}{W} \frac{d_{m}}{d_{c}} false(C false(t false) - C_{m} false) = - λ false(C false(t false) - C_{m} false),

where C m and d m are the mean concentration and mean depth in the main channel, respectively. We can calculate the exchange velocity E from the transverse velocity at the interface, following the methodology of Weitbrecht et al (; see also Mignot et al, ; Tuna et al, ):

E = \frac{1}{2 S_{e x}} \int_{S_{e x}} \overset{false| v false(x, z false) false|}{true} normald S,

where S ex is the total area of the interface section. The value of the exchange coefficient k is then obtained as the ratio between velocity exchange scale and the bulk velocity, k = E / U b .…”

Section: Mass Transportmentioning

confidence: 99%

“…where C m and d m are the mean concentration and mean depth in the main channel, respectively. We can calculate the exchange velocity E from the transverse velocity at the interface, following the methodology of Weitbrecht et al (2008;see also Mignot et al, 2016;Tuna et al, 2013):…”

Section: Mass Transportmentioning

confidence: 99%

“…Jackson et al (2013) also derived empirical equations based on nondimensional parameters of the flow to estimate the mean residence time in SSZs, considering the bed roughness in natural conditions. Despite the importance of the dynamics of turbulent flows in SSZs and their consequences on contaminant transport that can affect the entire watershed, most models of mass exchange with lateral recirculating flows have focused on idealized or simplified configurations (Drost et al, 2014;Jackson et al, 2015;Kimura & Hosoda, 1997;Tuna et al, 2013), with the exception of the studies carried out by Jackson et al (2012). Improving our understanding of the large-scale dynamics of coherent structures in realistic SSZs with natural geometries is thus critical to identify the connections of physical processes across scales and to determine the fundamental mechanisms of transport in the channel and their interactions with morphology.…”

Section: Introductionmentioning

confidence: 99%

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Field and Numerical Investigation of Transport Mechanisms in a Surface Storage Zone

et al. 2019

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In‐stream surface storage zones (SSZs) caused by lateral recirculation areas play a significant role in the transport and fate of contaminants in rivers. Lateral recirculating areas have long residence times that favor nutrient uptake, accumulation of pollutants, and interactions with reactive sediments. In watersheds affected by acid‐mine drainage, SSZs have profound effects on biogeochemical processes, controlling the local concentration and distribution of toxic elements along the channel. Despite the importance of turbulent flow dynamics on these processes, limited work has been carried out to analyze mass transport in natural SSZs with complex geometries. In this investigation we study a SSZ in the Lluta River, located in a high‐altitude environment in northern Chile, by coupling field measurements and 3‐D numerical simulations to understand the transport mechanisms with the main channel. We measure the velocity field using an acoustic Doppler velocimeter (ADV) and large‐scale particle image velocimetry (LSPIV), extracting the bathymetry from digital image processing. Using these data, we perform detached‐eddy simulations (DES) to analyze the mean flow, turbulence statistics, and the dynamics of large‐scale coherent structures. From this detailed description of the turbulent flow, we study the mass exchange and the time evolution of the mean concentration of a passive scalar in the SSZ by testing three upscaled models: a classical linear transport model, a two‐storage formulation, and a fractional transport model. The analysis integrates temporal and spatial scales to provide a new perspective on the turbulent flow in SSZs and their effects on global mass transport in rivers.

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