Soft transition between subcritical and supercritical currents through intermittent cascading interfacial instabilities

Salinas, Jorge S.; Balachandar, S.; Shringarpure, Mrugesh; Fedele, J. J.; Hoyal, D. C. J. D.; Cantero, Mariano I.

doi:10.1073/pnas.2008959117

Cited by 17 publications

(15 citation statements)

References 44 publications

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“…However, the dynamics of gravity flows undergoing hydraulic jumps over scours within a subaqueous channel system has been examined (Sumner et al, 2013;Dorrell et al, 2016). Alongside these experiments and field measurements, we highlight numerical simulations and physical experiments where flows change from supercritical to subcritical in the absence of a hydraulic jump (García, 1993;Kostic and Parker, 2006;Kostic and Parker, 2007;Salinas et al, 2020), and discuss the potential implications for channel mouth settings.…”

Section: Insights From Physical Experiments Numerical Simulations And...mentioning

confidence: 99%

“…However, this situation is unlikely to apply to CLTZs, or CMEZs, given their dominantly erosional nature. Nevertheless recent work has illustrated that there may be a mechanism by which finergrained flows can transition from supercritical to subcritical flows in the absence of a hydraulic jump (Salinas et al, 2020). They used a direct numerical simulation of subaqueous dilute particulate density currents (concentration is not given; particles have zero settling velocity), on a constant slope (0.72 °), and showed a change from supercritical to subcritical flow in the absence of a hydraulic jump.…”

Section: Transition From Supercritical To Subcritical Flow Without a ...mentioning

confidence: 99%

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Submarine Channel Mouth Settings: Processes, Geomorphology, and Deposits

2022

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Observations from the modern seafloor that suggest turbidity currents tend to erode as they lose channel-levee confinement, rather than decelerating and depositing their sediment load, has driven investigations into sediment gravity flow behaviour at the mouth of submarine channels. Commonly, channel mouth settings coincide with areas of gradient change and play a vital role in the transfer of sediment through deep-water systems. Channel mouth settings are widely referred to as the submarine channel-lobe transition zone (CLTZ) where well-defined channel-levees are separated from well-defined lobes, and are associated with an assemblage of erosional and depositional bedforms (e.g., scours and scour fields, sediment waves, incipient channels). Motivated by recently published datasets, we reviewed modern seafloor studies, which suggest that a wide range of channel mouth configurations exist. These include traditional CLTZs, plunge pools, and distinctive long and flared tracts between channels and lobes, which we recognise with the new term channel mouth expansion zones (CMEZs). In order to understand the morphodynamic differences between types of channel mouth settings, we review insights from physical experiments that have focussed on understanding changes in process behaviour as flows exit channels. We integrate field observations and numerical modelling that offer insight into flow behaviours in channel mouth settings. From this analysis, we propose four types of channel mouth setting: 1) supercritical CMEZs on slopes; 2) plunge pools at steep slope breaks with high incoming supercritical Froude numbers; 3) CLTZs with arrays of hydraulic jumps at slope breaks with incoming supercritical Froude numbers closer to unity; and, 4) subcritical CLTZs associated with slope breaks and/or flow expansion. Identification of the stratigraphic record of channel mouth settings is complicated by the propagation, and avulsion, of channels. Nonetheless, recent studies from ancient outcrop and subsurface systems have highlighted the dynamic evolution of interpreted CLTZs, which range from composite erosion surfaces, to tens of metres thick stratigraphic records. We propose that some examples be reconsidered as exhumed CMEZs.

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Section: Insights From Physical Experiments Numerical Simulations And...mentioning

confidence: 99%

Section: Transition From Supercritical To Subcritical Flow Without a ...mentioning

confidence: 99%

Submarine Channel Mouth Settings: Processes, Geomorphology, and Deposits

2022

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“…(2) in conjunction with the scalar transport and Boussinesq approximation Eqs. ( 15)-( 17) is a well-posed problem, and has been used with great success to model turbidity currents [2, 84,85,162]. However, this framework is limited to the assumption of a dilute suspension with only small density difference compared to the clear water ambient fluid.…”

Section: Rheology Modelingmentioning

confidence: 99%

Incorporating grain-scale processes in macroscopic sediment transport models

Vowinckel¹

2021

Acta Mech

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Sediment transport simulations face the challenge of accounting for vastly different scales in space and time that cannot be tackled by a unifying approach. Instead, processes are subdivided into a microscale at the particle level, a mesoscale of a large finite number of particles, and a macroscale that computes the sediment motion by means of advection–diffusion equations. The different processes occurring at different scales are simulated using different computational approaches. However, modeling sediment transport at multiple scales with high fidelity requires proper closure arguments that interconnect the different processes. Ultimately, we will need efficient macroscale models that can readily be utilized for engineering practices covering, e.g., entire river reaches or even estuaries. In recent years, highly resolved simulations have become a valuable tool to provide these closure arguments for sediment transport models on the continuum scale. In this paper, we will review the most relevant approaches to simulate sediment transport at different scales and discuss the perspectives of four most promising modeling techniques that can help to improve sediment transport modeling. On the grain scale, these enhancements include the impact of mechanical properties of cohesion and biocohesion as well as the shape of non-spherical sediment grains on fluid–particle and particle–particle interactions. On larger scales, we review constitutive equations for the macroscopic rheological behavior of sediment beds that may decouple the relevant scales for fluid and sediment motion. Furthermore, we discuss machine learning strategies as an efficient means to derive scaling arguments across multiple scales.

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“…An interesting observation is that the transition from supercritical to subcritical state is not abrupt. As discussed in Salinas et al (2020), the transition occurs through a third transcritical state, where the flow exhibits a cyclic behaviour by continually transitioning back and forth between supercritical-and subcritical-like states.…”

Section: Introductionmentioning

confidence: 97%

“…Depending on the slope of the bed, three different flow regimes have been identified (Sequeiros 2012;Salinas et al 2020Salinas et al , 2021bSalinas, Balachandar & Cantero 2021a). At steeper slopes of S 0.05, the current evolves to a near-self-similar supercritical state, which is characterized by a turbulent near-wall layer close to the bottom boundary and a turbulent interface layer where the current vigorously mixes with the ambient (Salinas et al 2021a).…”

Section: Introductionmentioning

confidence: 99%

Slope dependence of self-similar structure and entrainment in gravity currents

et al. 2022

Self Cite

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Results from seven direct and large-eddy simulations of gravity currents on slopes ranging from 0.14 $^{\circ }$ to 2.86 $^{\circ }$ that span from the subcritical to the supercritical regime are studied. By considering a long domain, attention is focused on the near-self-similar state approached by these currents far downstream. In the self-similar limit, the various shape factors, local Richardson number, entrainment coefficient, velocity scale and basal drag coefficient reach a constant value, while the current height, volume and momentum fluxes continue to increase linearly. Their dependence on slope is presented.

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Soft transition between subcritical and supercritical currents through intermittent cascading interfacial instabilities

Cited by 17 publications

References 44 publications

Submarine Channel Mouth Settings: Processes, Geomorphology, and Deposits

Submarine Channel Mouth Settings: Processes, Geomorphology, and Deposits

Incorporating grain-scale processes in macroscopic sediment transport models

Slope dependence of self-similar structure and entrainment in gravity currents

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