Spatially-averaged momentum fluxes and stresses in flows over mobile granular beds: a DNS-based study

Vowinckel, Bernhard; Nikora, Vladimir; Kempe, Tobias; Fröhlich, Jochen

doi:10.1080/00221686.2016.1260658

Cited by 28 publications

(32 citation statements)

References 40 publications

(56 reference statements)

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“…Since the Gibson theory was derived for pure muds in the first place, applying the model to sand-mud mixtures might be problematic [38]. At the same time, the larger sized particles render the physical configuration attractive for phase-resolved simulations that allow for a full description of the fluid and the particle motion [39][40][41][42][43][44].…”

Section: Introductionmentioning

confidence: 99%

Consolidation of freshly deposited cohesive and noncohesive sediment: Particle-resolved simulations

et al. 2019

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We analyze the consolidation of freshly deposited cohesive and non-cohesive sediment by means of particle-resolved direct Navier-Stokes simulations based on the Immersed Boundary Method. The computational model is parameterized by material properties and does not involve any arbitrary calibrations. We obtain the stress balance of the fluid-particle mixture from first principles and link it to the classical effective stress concept. The detailed datasets obtained from our simulations allow us to evaluate all terms of the derived stress balance. We compare the settling of cohesive sediment to its non-cohesive counterpart, which corresponds to the settling of the individual primary particles. The simulation results yield a complete parameterization of the Gibson equation, which has been the method of choice to analyze self-weight consolidation. arXiv:1907.03700v1 [cond-mat.soft]

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Section: Introductionmentioning

confidence: 99%

Consolidation of freshly deposited cohesive and noncohesive sediment: Particle-resolved simulations

et al. 2019

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“…11a and 11b) directly reflects the distribution of φ VT reported in Vowinckel, Nikora, et al (2017). In the outer flow field the momentum supply is constant (as the porosity is equal to 1), while it decreases in the near-wall region, reflecting the decrease in porosity (Fig.…”

Section: Spatial Variability Of the Terms Of The Longitudinal Double-mentioning

confidence: 97%

“…In the companion paper by Vowinckel, Nikora, et al (2017) the knowledge gained from the present study is further exploited to compute momentum fluxes, the bulk momentum balance, and the modified resistance of the mobile granular bed to the flow as well the structure of secondary currents due to ridge effects. Chan-Braun for stimulating discussions on bed-load transport.…”

Section: Discussionmentioning

confidence: 99%

Momentum balance in flows over mobile granular beds: application of double-averaging methodology to DNS data

Vowinckel

Nikora

Kempe

et al. 2017

Journal of Hydraulic Research

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This paper presents the application of the double-averaging methodology to actual data obtained for the mobile-bed conditions from direct numerical simulations using an immersed boundary method. The dimensions of the computational domain resemble those for open-channel flows with small relative submergence. The domain bottom is a plane covered with one layer of hexagonally packed, single-size spheres fixed to the bed. The fixed particles are covered by 2000 mobile particles of the same size that are free to move. Two simulation scenarios at distinctly different values of the Shields parameter are studied representing a fully mobilized and partially mobilized granular bed. The effects of the averaging time and the averaging domain size and shape on the double-averaged flow quantities are identified first. Then, the data analysis focuses on the detailed assessment of the key terms of the double-averaged momentum balance equation formulated for mobile-bed conditions. The paper demonstrates that the double-averaging methodology provides an efficient reduction of the massive datasets produced by the fully resolved simulations to a manageable number of physically meaningful double-averaged quantities, which should help devising closure strategies for modelling mobile-bed flows.

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“…We have also used the fact that µ f , ρ f , and f b,x are constant throughout the domain. Note that this form is equivalent to the double-averaged momentum balance analyzed in [4] since there are no fluctuations or unsteady effects for the present scenario of a laminar flow, but the interfacial terms of the DAM framework had been replaced by the particle stress.…”

Section: Momentum Balances 31 Momentum Balance For the Fluid Phasementioning

confidence: 99%

“…Recently, this topic has seen a big push through the formulation of the Double Averaging Methodology [DAM, 1,2]. In particular, applying this concept to datasets generated by particle-resolving Direct Numerical Simulations (DNS) employing the Immersed Boundary Method (IBM) has provided great insights into the fundamental physical mechanisms governing of complex multiphase flows [e.g 3,4]. These studies have revealed the importance of the nonlinear terms of the double-averaged momentum budget.…”

Section: Introductionmentioning

confidence: 99%

Stress balance for a viscous flow with a single rolling particle

et al. 2018

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One of the most important aspects in hydraulic engineering is to describe flows over mobile porous media in a continuum sense to derive models for sediment transport. This remains a challenging task due to the complex coupling of the particle and the fluid phase. Computational Fluid Dynamics can provide the data needed to understand the coupling of the two phases. To this end, we carry out grain-resolving Direct Numerical Simulations of multiphase flow. The particle phase is introduced by the Immersed Boundary Method and the particle-particle interaction is described by a sophisticated Discrete Element Method. We derive the stress budgets of the fluid and the particle phases separately through a rigorous analysis of the governing equations using the Double Averaging Methodology and the Coarse-Graining Method. As a next step, we perform a simple simulation of a heavy particle exposed to a Poiseuille flow rolling along a wall to understand the physical implications of the fluid-particle coupling. All terms of the stress balances can be computed in a straightforward manner allowing to close the budgets for the two phases separately. However, we encounter problems when attempting to combine the fluid-resolved local stresses with the coarse-grained particle stresses into a single balance for the fluid-particle mixture.

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Spatially-averaged momentum fluxes and stresses in flows over mobile granular beds: a DNS-based study

Cited by 28 publications

References 40 publications

Consolidation of freshly deposited cohesive and noncohesive sediment: Particle-resolved simulations

Consolidation of freshly deposited cohesive and noncohesive sediment: Particle-resolved simulations

Momentum balance in flows over mobile granular beds: application of double-averaging methodology to DNS data

Stress balance for a viscous flow with a single rolling particle

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