Flocculation of suspended cohesive particles in homogeneous isotropic turbulence

Zhao, Kunpeng; Pomes, Florian; Vowinckel, Bernhard; Hsu, Tian‐Jian; Bai, Bo; Meiburg, Eckart

doi:10.1017/jfm.2021.487

Cited by 19 publications

(36 citation statements)

References 83 publications

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“…The lubrication theory suppresses the rebound velocity after the collision (Chen et al., 2019; Zhao et al., 2021), because the fluid between two approaching particles gets squeezed out of the gap and produces a significant resistance to the collision. In this study, we used a small coefficient of restitution of the particles instead to damp the energy because we included a short‐range DVLO interaction, which can overcome the short‐range lubrication force.…”

Section: Methodsmentioning

confidence: 99%

Particle Nonresolved DNS‐DEM Study of Flocculation Dynamics of Cohesive Sediment in Homogeneous Isotropic Turbulence

Balachandar

2022

Water Resources Research

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Cohesive sediment transport is important for many geophysical and engineering applications, for example, the rapid siltation in navigation channels and harbors (Hayter & Mehta, 1986;Winterwerp et al., 2000), cohesive sediment transport in salt marsh (Graham & Manning, 2007) and long-term delta morphology (Edmonds & Slingerland, 2010). Cohesive sediment can absorb pollutants (e.g., heavy metals, pesticides and nutrients) and is a concern for water quality (Ongley et al., 1992). Modeling suspended sediment dynamics is also essential for the understanding of biogeochemical cycles. Transport of estuarine and nearshore cohesive sediment therefore plays an important role in coastal processes and the functioning of healthy ecosystems (Grabowski et al., 2011;Deegan et al., 2012). Settling velocity is one of the key parameters in sediment transport. Cohesive sediment can bind together to form flocs and large flocs can breakup by shear. A floc size distribution often develops in sediment suspension and flocs of different size will settle at different velocities. The settling velocity of cohesive sediment strongly depends on the flocculation dynamics (Winterwerp & Van Kesteren, 2004). However, due to complex surface physico-chemical and biological properties of cohesive sediment, cohesive sediment dynamics are complex and empirically parameterized (Winterwerp et al., 2006;Kuprenas et al., 2018). It is fundamentally important to understand the cohesive sediment dynamics in natural environment, in particular how flow turbulence affects the flocculation dynamics, and hence the floc size distribution and the settling velocity.Flocculation plays an important role in cohesive sediment transport. To represent flocculation of cohesive sediment more realistically, models based on either characteristic floc diameter (Winterwerp, 1998;Son & Hsu, 2008) or size-classes (McAnally & Mehta, 2002;Maerz et al., 2011) have been developed. Models based on the characteristic floc diameter simply assume flocs to have a single equilibrium size, which can either be derived from a single-class population balance equation or empirical equations (Maggi, 2009). Kuprenas et al. (2018) improved the Winterwerp model (Winterwerp, 1998) to consider the upper limit on floc size due to turbulent shear. However, bimodal floc size distribution (FSD) with the first peak around microflocs by direct contact

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Section: Methodsmentioning

confidence: 99%

Particle Nonresolved DNS‐DEM Study of Flocculation Dynamics of Cohesive Sediment in Homogeneous Isotropic Turbulence

Balachandar

2022

Water Resources Research

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“…So we set the computational domain width to W = 2.5 in the parametric study to be described below. We remark that the present cohesive force implementation has been validated carefully by Vowinckel et al (2019b) for the settling process of polydisperse sediments in quiescent fluid, and by Zhao et al (2020Zhao et al ( , 2021 for the flocculation of suspended particles in turbulence.…”

Section: Validationmentioning

confidence: 97%

“…(2019 a , b ) to estimate the cohesion between rough particles, as implemented in Zhao et al. (2020, 2021). The Hamaker constant is a function of the particle and fluid properties, is the range of the cohesive force, and is the microscopic size of surface asperities.…”

Section: Computational Modelmentioning

confidence: 99%

“…(2019 b ) for the settling process of polydisperse sediments in quiescent fluid, and by Zhao et al. (2020, 2021) for the flocculation of suspended particles in turbulence.…”

Section: Computational Modelmentioning

confidence: 99%

“…Also, u n,cp and u t,cp are the normal and tangential components of the relative velocity at the surface contact point, respectively, k n and d n are the normal stiffness and damping coefficients, k t and d t are the tangential stiffness and damping coefficients, ζ t is the tangential displacement integrated over the time interval for which the two particles are in contact, t is the direction of the tangential force, and μ p is the friction coefficient between the two surfaces. We employ the cohesive force model proposed by Vowinckel et al (2019a,b) to estimate the cohesion between rough particles, as implemented in Zhao et al (2020Zhao et al ( , 2021…”

Section: Governing Equationsmentioning

confidence: 99%

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Grain-resolving simulations of submerged cohesive granular collapse

Zhu

Zhao

et al. 2022

J. Fluid Mech.

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We investigate the submerged collapse of weakly polydisperse, loosely packed cohesive granular columns, as a function of aspect ratio and cohesive force strength, via grain-resolving direct numerical simulations. The cohesive forces act to prevent the detachment of individual particles from the main body of the collapsing column, reduce its front velocity, and yield a shorter and thicker final deposit. All of these effects can be captured accurately across a broad range of parameters by piecewise power-law relationships. The cohesive forces reduce significantly the amount of available potential energy released by the particles. For shallow columns, the particle and fluid kinetic energy decreases for stronger cohesion. For tall columns, on the other hand, moderate cohesive forces increase the maximum particle kinetic energy, since they accelerate the initial free-fall of the upper column section. Only for larger cohesive forces does the peak kinetic energy of the particles decrease. Computational particle tracking indicates that the cohesive forces reduce the mixing of particles within the collapsing column, and it identifies the regions of origin of those particles that travel the farthest. The simulations demonstrate that cohesion promotes aggregation and the formation of aggregates. Furthermore, they provide complete information on the temporally and spatially evolving network of cohesive and direct contact force bonds. While the normal contact forces are aligned primarily in the vertical direction, the cohesive bonds adjust their preferred spatial orientation throughout the collapse. They result in a net macroscopic stress that counteracts deformation and slows the spreading of the advancing particle front.

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A Modeling framework for flocculated cohesive sediment transport in the current bottom boundary layer

Penaloza-Giraldo,

Yue,

Hsu

et al. 2025

Advances in Water Resources

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Flocculation of suspended cohesive particles in homogeneous isotropic turbulence

Abstract: Abstract

Cited by 19 publications

References 83 publications

Particle Nonresolved DNS‐DEM Study of Flocculation Dynamics of Cohesive Sediment in Homogeneous Isotropic Turbulence

Particle Nonresolved DNS‐DEM Study of Flocculation Dynamics of Cohesive Sediment in Homogeneous Isotropic Turbulence

Grain-resolving simulations of submerged cohesive granular collapse

A Modeling framework for flocculated cohesive sediment transport in the current bottom boundary layer

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