High‐resolution numerical simulations of resuspending gravity currents: Conditions for self‐sustainment

Blanchette, Francois; Strauss, M.; Meiburg, Eckart; Kneller, Benjamin Charles; Glinsky, Michael E.

doi:10.1029/2005jc002927

Cited by 93 publications

(118 citation statements)

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“…The lateral development of density-driven flow in a subaqueous channel is studied using a 3D numerical model, in the work of Imran et al [20]. The conditions under which turbidity currents may become selfsustaining through particle entrainment are investigated in the work of Blanchette et al [21], using 2D Direct Numerical Simulations of resuspending gravity currents. A numerical model of turbidity currents with a deforming bottom boundary, that predicts the vertical structure of the flow velocity and concentration as well as the change in the bed level, due to erosion and deposition of suspended sediment, is developed in the work of Huang et al [22].…”

Section: Introductionmentioning

confidence: 99%

3D numerical modelling of turbidity currents

et al. 2010

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During floods, the density of river water usually increases due to a subsequent increase in the concentration of the suspended sediment that the river carries, causing the river to plunge underneath the free surface of a receiving water basin and form a turbidity current that continues to flow along the bottom. The study and understanding of such complex phenomena is of great importance, as they constitute one of the major mechanisms for suspended sediment transport from rivers into oceans, lakes or reservoirs. Unlike most of the previous numerical investigations on turbidity currents, in this paper, a 3D numerical model that simulates the dynamics and flow structure of turbidity currents, through a multiphase flow approach is proposed, using the commercial CFD code FLUENT. A series of numerical simulations that reproduce particular published laboratory flows are presented. The detailed qualitative and quantitative comparison of numerical with laboratory results indicates that apart from the global flow structure, the proposed numerical approach efficiently predicts various important aspects of turbidity current flows, such as the effect of suspended sediment mixture composition in the temporal and spatial evolution of the simulated currents, the interaction of turbidity currents with loose sediment bottom layers and the formation of internal hydraulic jumps. Furthermore, various extreme cases among the numerical runs considered are further analyzed, in order to identify the importance of various controlling flow parameters.

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Section: Introductionmentioning

confidence: 99%

3D numerical modelling of turbidity currents

et al. 2010

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“…There has been some success in modelling these flows using DNS in two dimensions which makes the problem more computationally tractable (Blanchette et al, 2005;Ooi et al, 2007). However, Espath et al (2014) showed that the only important diagnostic that can be accurately predicted using a two-dimensional DNS model is the sedimentation rate.…”

Section: S D Parkinson Et Al: Direct Numerical Simulations Of Partmentioning

confidence: 99%

Direct numerical simulations of particle-laden density currents with adaptive, discontinuous finite elements

2014

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Abstract. High-resolution direct numerical simulations (DNSs) are an important tool for the detailed analysis of turbidity current dynamics. Models that resolve the vertical structure and turbulence of the flow are typically based upon the Navier-Stokes equations. Two-dimensional simulations are known to produce unrealistic cohesive vortices that are not representative of the real three-dimensional physics. The effect of this phenomena is particularly apparent in the later stages of flow propagation. The ideal solution to this problem is to run the simulation in three dimensions but this is computationally expensive. This paper presents a novel finite-element (FE) DNS turbidity current model that has been built within Fluidity, an open source, general purpose, computational fluid dynamics code. The model is validated through re-creation of a lock release density current at a Grashof number of 5 × 10 6 in two and three dimensions. Validation of the model considers the flow energy budget, sedimentation rate, head speed, wall normal velocity profiles and the final deposit. Conservation of energy in particular is found to be a good metric for measuring model performance in capturing the range of dynamics on a range of meshes. FE models scale well over many thousands of processors and do not impose restrictions on domain shape, but they are computationally expensive. The use of adaptive mesh optimisation is shown to reduce the required element count by approximately two orders of magnitude in comparison with fixed, uniform mesh simulations. This leads to a substantial reduction in computational cost. The computational savings and flexibility afforded by adaptivity along with the flexibility of FE methods make this model well suited to simulating turbidity currents in complex domains.

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“…This model is used to describe the erosion of sediment from a cohesive bed or from a bed of fine cohesionless material where some critical shear stress must be exceeded in order to entrain particles from the bed into the water column [2,9,10,[15][16][17].…”

Section: Model Developmentmentioning

confidence: 99%

Sediment transport via dam-break flows over sloping erodible beds

Emmett

Moodie

2009

Computational Methods in Multiphase Flow V

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When a semi-infinite body of homogeneous fluid initially at rest behind a vertical retaining wall is suddenly released by the removal of the barrier, the resulting flow over a horizontal or sloping bed is referred to as a dam-break flow. When bed resistance is neglected the exact solution, in the case of a stable horizontal bed, may be obtained on the basis of shallow-water theory via the method of characteristics and the results are well known. Discrepancies between these shallow-water based solutions and experiments have been partially accounted for by the introduction of flow resistance in the form of basal friction. This added friction significantly modifies the wave speed and flow profile near the head of the wave so that the simple exact solutions no longer apply. Various asymptotic or numerical approaches must be implemented to solve these frictionally modified depth-averaged shallow-water equations. When the bed is no longer stable so that solid particles may be exchanged between the bed and the fluid, the dynamics of the flow become highly complex as the buoyancy forces vary in space and time according to the competing rates of erosion and deposition. It is our intention here to study dam-break flows over erodible sloping beds as agents of sediment transport, taking into account basal friction as well as the effects of particle concentrations on flow dynamics including both erosion and deposition. We shall consider shallow flows over initially dry beds and investigate the effects of changes in the depositional and erosional models employed, in the nature of the drag acting on the flow, and in the slope of the bed. These models include effects hitherto neglected in previous studies and offer insights into the transport of sediment in the worst case scenario of the complete and instantaneous collapse of a dam.

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High‐resolution numerical simulations of resuspending gravity currents: Conditions for self‐sustainment

Cited by 93 publications

References 50 publications

3D numerical modelling of turbidity currents

3D numerical modelling of turbidity currents

Direct numerical simulations of particle-laden density currents with adaptive, discontinuous finite elements

Sediment transport via dam-break flows over sloping erodible beds

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