A numerical investigation of fine sediment resuspension in the wave boundary layer—Uncertainties in particle inertia and hindered settling

Cheng, Zhen; Yu, Xiao; Hsu, Tian‐Jian; Balachandar, S.

doi:10.1016/j.cageo.2015.07.009

Cited by 4 publications

(3 citation statements)

References 49 publications

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“…A fluid mud‐induced wave damping algorithm developed by Winterwerp et al (2007) was included in SWAN and applied to the Guyana coastal system. Prior turbulence‐resolving simulations in particle‐laden flow also suggest the complexity of turbulence‐sediment interactions due to sediment‐induced stable density stratification, bed erosion, and hindered settling (Cheng, Yu, Hsu, & Balachandar, 2015; Hsu et al, 2009; Ozdemir et al, 2010, 2011). Therefore, a realistic fluid mud transport simulation in the future should incorporate different types of sediment particles and two‐way coupling between sediment dynamics and hydrodynamics to achieve more robust results.…”

Section: Discussionmentioning

confidence: 99%

A Numerical Investigation of Wave‐Supported Gravity Flow During Cold Fronts Over the Atchafalaya Shelf

Zang

Xue

et al. 2020

JGR Oceans

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Wave‐supported fluid mud (WSFM) plays an important role in sediment downslope transport on the continental shelves. In this study, we incorporated WSFM processes in the wave boundary layer (WBL) into the Community Sediment Transport Modeling System (CSTMS) on the platform of the Coupled Ocean‐Atmosphere‐Wave‐and‐Sediment Transport modeling system (COAWST). The WSFM module was introduced between the bottommost water layer and top sediment layer, which accounted for the key sediment exchange processes (e.g., resuspension, vertical settling, diffusion, and horizontal advection) at the water‐WBL and WBL‐sediment bed boundaries. To test its robustness, we adapted the updated model (CSTMS + WBL) to the Atchafalaya shelf in the northern Gulf of Mexico and successfully reproduced the sediment dynamics in March 2008, when active WSFM processes were reported. Compared with original CSTMS results, including WSFM module weakened the overall intensity of sediment resuspension, and the CSTMS + WBL model simulated a lutocline between the WBL and overlying water due to the formation of WSFM. Downslope WSFM transport resulted in offshore deposition (>4 cm), which greatly changed the net erosion/deposition pattern on the inner shelf off the Chenier Plain. WSFM flux was comparable with suspended sediment flux (SSF) off the Atchafalaya Bay, and it peaked along the Chenier Plain coast where wave activities were strong and the bathymetric slope was steep. The influence of fluvial sediment supply on sediment dynamics was limited in the Atchafalaya Bay. Sensitivity tests of free settling, flocculation, and hindered settling effects suggested that sediments were transported further offshore due to reduced settling velocity in the WBL once fluid mud was formed. Although sediment concentration in the WBL was sensitive to surface sediment critical shear stress, cohesive bed behavior was less important in WSFM dynamics when compared with strong hydrodynamic during cold fronts.

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Section: Discussionmentioning

confidence: 99%

A Numerical Investigation of Wave‐Supported Gravity Flow During Cold Fronts Over the Atchafalaya Shelf

Zang

Xue

et al. 2020

JGR Oceans

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“…Findings suggest that higher bed shear stresses can trigger a situation in which a positive feedback between hindered settling and the net erosion flux leads to rapidly increasing suspended-mud concentrations towards the gelling point, a mechanism that we termed "gelling ignition" (Figure 2). A recent three-dimensional model application [13] confirms and discusses the existence of this mechanism. The viscosity of fluid mud substantially increases at higher concentrations near the gelling point [14] and fluid mud becomes governed by non-Newtonian effects [15].…”

Section: Introductionmentioning

confidence: 67%

Wave-Created Mud Suspensions: A Theoretical Study

Kämpf

Myrow

2018

JMSE

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We studied wave-created high-density mud suspensions (fluid mud) using a one-dimensional water column (1DV) model that includes k-ε turbulence closure at a high vertical resolution with a vertical grid spacing of 1 mm. The k-ε turbulence model includes two sediment-related dissipation terms associated with vertical density stratification and viscous drag of flows around sediment particles. To this end, the calibrated model reproduces the key characteristics (maximum concentration and thickness) of fluid mud layers created in laboratory experiments over a large range of wave velocities from 10 to 55 cm/s. The findings demonstrate that the equilibrium near-bed mud concentration, C b , is solely determined from the balance between erosion and deposition fluxes, whereas the thickness of the fluid mud layer is mainly controlled by sediment-induced density stratification, which dissipates turbulence and hence eliminates turbulent sediment diffusivity at the top of the fluid mud layer, the lutocline. Our model stands in contrast to those that suggest that upward sediment diffusion is close to zero at the interface between the fluid mud layer and the overlying fluid. Instead, our model suggests that the upward diffusive flux of fluid mud flows peak at the lutocline and is compensated for enhanced settling fluxes just above it. Our model findings also support the existence of the gelling-ignition process, which is critical for the development of fluid mud beds in modern sedimentary environments.

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“…Likewise, the stable stratification resulting from wave-induced resuspension of bottom sediments has been seen to both damp turbulent kinetic energy and reduce the bed shear stress [13]. The interaction between this damping and the turbulent resuspension and transport of muddy sediment is not yet fully understood, but recent research has indicated a strong relationship between small scale turbulence in the bottom boundary layer and the movement of fine muddy sediment [14,15]. Two-phase modeling has been used to show that the boundary layer thickness of fine sediment suspension is increased by the complex interplay between flow instabilities, stress terms, and sediment-induced turbulence attenuation [16].…”

Section: Introductionmentioning

confidence: 99%

A Bingham Plastic Fluid Solver for Turbulent Flow of Dense Muddy Sediment Mixtures

Adams

Simeonov

Bateman

et al. 2023

Fluids

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We have developed and tested a numerical model for turbulence resolving simulations of dense mud–water mixtures in oscillatory bottom boundary layers, based on a low Stokes number formulation of the two-phase equations. The resulting non-Boussinesq equation for the fluid momentum is coupled to a transport equation for the mud volumetric concentration, giving rise to a volume-averaged fluid velocity that is non-solenoidal, and the model was implemented as a new compressible flow solver. An oscillating pressure gradient force was implemented in the correction step of the standard semi-implicit method for pressure linked equations (SIMPLE), for consistency with the treatment of other volume forces (e.g., gravity). The flow solver was further coupled to a new library for Bingham plastic materials, in order to model the rheological properties of dense mud mixtures using empirically determined concentration-dependent yield stress and viscosity. We present three direct numerical simulation tests to validate the new MudMixtureFoam solver against previous numerical solutions and experimental data. The first considered steady flow of Bingham plastic fluid with uniform concentration around a sphere, with Bingham numbers ranging from 1 to 100 and Reynolds numbers ranging from 0.1 to 100. The second considered the development of turbulence in oscillatory bottom boundary layer flow, and showed the formation of an intermittently turbulent layer with peak velocity perturbations exceeding 10 percent of the freestream flow velocity and occurring at a distance from the bottom comparable to the Stokes boundary layer thickness. The third considered the effects of density stratification due to resuspended sediment on turbulence in oscillatory bottom boundary layer flow with a bulk Richardson number of 1×10−4 and a Stokes–Reynolds number of 1000, and showed the formation of a lutocline between 20 and 40 Stokes boundary layer depths. In all cases, the new solver produced excellent agreement with the previous results.

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A numerical investigation of fine sediment resuspension in the wave boundary layer—Uncertainties in particle inertia and hindered settling

Cited by 4 publications

References 49 publications

A Numerical Investigation of Wave‐Supported Gravity Flow During Cold Fronts Over the Atchafalaya Shelf

A Numerical Investigation of Wave‐Supported Gravity Flow During Cold Fronts Over the Atchafalaya Shelf

Wave-Created Mud Suspensions: A Theoretical Study

A Bingham Plastic Fluid Solver for Turbulent Flow of Dense Muddy Sediment Mixtures

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