Properties of the Body of a Turbidity Current at Near‐Normal Conditions: 2. Effect of Settling

Salinas, Jorge S.; Cantero, Mariano I.; Shringarpure, Mrugesh; Balachandar, S.

doi:10.1029/2019jc015335

Cited by 8 publications

(13 citation statements)

References 36 publications

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“…Even for sediment particles of size 10 μm their nondimensional settling velocity can be considered small (i.e., settling velocity is much smaller than the friction velocity, which is the characteristic velocity of the flow). As we see in the companion work (Salinas et al, 2019) the effect of settling becomes important only at much larger sediment sizes. The time scale is H∕u * and the pressure scale is u 2 * .…”

Section: 1029/2019jc015332mentioning

confidence: 60%

“…In this work we consider turbidity currents where the suspended sediment is very fine (negligible settling velocity). We study the effect of nonzero settling velocity in the companion work Salinas et al ().…”

Section: Discussionmentioning

confidence: 99%

“…Moreover, we neglect the effect of settling velocity of sediment by setting

\overset{V}{true} = 0

. We study the effect of this parameter in the companion work (Salinas et al, ). It must be emphasized that the moderate value of Re τ chosen is orders of magnitude smaller than field values.…”

Section: Mathematical and Numerical Setupmentioning

confidence: 99%

“…Note that in the present work settling velocity is set to zero (

\overset{V}{true} = 0

, see Figure b). We study the effect of this parameter in the companion work (Salinas et al, ). In the present case of a sediment‐driven current, this results in a turbulent channel flow with uniform sediment concentration.…”

Section: Mathematical and Numerical Setupmentioning

confidence: 99%

“…Furthermore, in the present work we will isolate the effect of bottom slope by considering the limit of very fine suspended sediment, whose settling effect can be ignored and the effective settling velocity can be set to zero. The effect of settling velocity on turbidity currents is studied in the companion work (Salinas et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Properties of the Body of a Turbidity Current at Near‐Normal Conditions: 1. Effect of Bed Slope

et al. 2019

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We study the body of turbidity currents in normal flow conditions by means of highly resolved direct numerical simulations of a homogeneous model. We focus on turbidity currents where the net amount of sediment is held fixed. We consider the sediment to be fine enough that their settling effect is neglected, and in the companion work we consider the effect of settling velocity. We consider five different shear Richardson numbers from 5 to 80. Under normal condition, basal drag and entrainment at the interface precisely balance the momentum supplied to the current from the excess weight of the sediment. The normal flow properties of a turbidity current can be fully characterized in terms of bulk Richardson number Ri and bulk Reynolds number Re. The velocity, concentration, and turbulent kinetic energy profiles take a self-similar shape when the current is at near-normal conditions. We observe the flow to display supercritical features for Ri ⪅ 0.4 and to display subcritical features for Ri ⪆ 0.7. From the behavior at intermediate Richardson numbers it appears that the transition between subcritical to supercritical behavior is not sharp. We observe good agreement between experimental and simulation results in both regimes. The entrainment coefficient as a function of bulk Richardson number at normal condition is in good agreement with the empirical relation and with available experimental results. We present a simple model for drag coefficient as a function of bulk Reynolds and Richardson numbers.

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Section: 1029/2019jc015332mentioning

confidence: 60%

Section: Discussionmentioning

confidence: 99%

“…Moreover, we neglect the effect of settling velocity of sediment by setting

\overset{V}{true} = 0

. We study the effect of this parameter in the companion work (Salinas et al, ). It must be emphasized that the moderate value of Re τ chosen is orders of magnitude smaller than field values.…”

Section: Mathematical and Numerical Setupmentioning

confidence: 99%

“…Note that in the present work settling velocity is set to zero (

\overset{V}{true} = 0

Section: Mathematical and Numerical Setupmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Properties of the Body of a Turbidity Current at Near‐Normal Conditions: 1. Effect of Bed Slope

et al. 2019

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Hydrodynamics and Sediment Transport of Downslope Turbidity Current Through Rigid Vegetation

Han

Lin

et al. 2023

Water Resources Research

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Systematical downslope‐turbidity‐current experiments were performed to clarify the relationship between sediment‐transport modes and current propagation patterns caused by rigid vegetation, as well as adjustments in turbulence characteristics of current. The equations for predicting the front velocities of downslope turbidity currents with emergent vegetation were proposed and validated via experimental data. Experimental results reveal that sediment deposition causes the lower turbulent kinetic energy (TKE) peaks of turbidity currents to decrease or even disappear without affecting their upper TKE peaks, while the rigid vegetation has the opposite effect. Vegetation stems destroy the longitudinal low‐high speed streaks associated with the quasi‐streamwise eddies in the near‐bed region and increase the proportions of the outward and inward interactions. In addition, sediment deposition severely suppresses the turbulent bursting events within turbidity currents but does not influence the relative proportions of the four bursting types. Rigid vegetation and sediment deposition both degrade the absolute values of the third‐order moments of velocity fluctuations without changing their signs to reduce the generation frequency of sweep events. Emergent rigid vegetation accelerates the formation of the reflected bore to provide energy for the deposited sediment to move downstream continuously. On the other hand, the dense submerged vegetation makes turbidity currents easily form the two‐head propagating mode, which allows part of the sediments carried by the upper current head to be transported downstream rather than deposited within or upstream of the vegetation region. Furthermore, the sloping boundary provides favorable conditions to initiate these specific modes for sediment transport adjusted by rigid vegetation.

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Anatomy of subcritical submarine flows with a lutocline and an intermediate destruction layer

et al. 2021

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Turbidity currents are sediment-laden flows that travel over a sloping bed under a stagnant ambient fluid, driven by the density difference between the current and the ambient. Turbidity currents transport large amounts of carbon, nutrients and fresh water through oceans and play an important role in global geochemical cycling and seafloor ecosystems. Supercritical currents are observed in steeper slopes. Subcritical currents are observed in milder slopes, where the near-bed and interface layers are prevented from interacting across the velocity maximum. Past works show the existence of such a barrier to vertical momentum transfer is essential for the body of the subcritical current to extend over hundreds of kilometers in length without much increase in height. Here we observe the body of subcritical currents to have a three layer structure, where the turbulent near-bed layer and the non-turbulent interface layer are separated by an intermediate layer of negative turbulence production. We explain the mechanism by which this layer prevents the near-bed turbulent structures from penetrating into the interface layer by transferring energy back from turbulence to the mean flow.

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Properties of the Body of a Turbidity Current at Near‐Normal Conditions: 2. Effect of Settling

Cited by 8 publications

References 36 publications

Properties of the Body of a Turbidity Current at Near‐Normal Conditions: 1. Effect of Bed Slope

Properties of the Body of a Turbidity Current at Near‐Normal Conditions: 1. Effect of Bed Slope

Hydrodynamics and Sediment Transport of Downslope Turbidity Current Through Rigid Vegetation

Anatomy of subcritical submarine flows with a lutocline and an intermediate destruction layer

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