Abstract

Abstract. In this paper, a three-dimensional two-phase flow solver, SedFoam-2.0, is presented for sediment transport applications. The solver is extended from twoPhaseEulerFoam available in the 2.1.0 release of the open-source CFD (computational fluid dynamics) toolbox OpenFOAM. In this approach the sediment phase is modeled as a continuum, and constitutive laws have to be prescribed for the sediment stresses. In the proposed solver, two different intergranular stress models are implemented: the kinetic theory of granular flows and the dense granular flow rheology μ(I). For the fluid stress, laminar or turbulent flow regimes can be simulated and three different turbulence models are available for sediment transport: a simple mixing length model (one-dimensional configuration only), a k − ε, and a k − ω model. The numerical implementation is demonstrated on four test cases: sedimentation of suspended particles, laminar bed load, sheet flow, and scour at an apron. These test cases illustrate the capabilities of SedFoam-2.0 to deal with complex turbulent sediment transport problems with different combinations of intergranular stress and turbulence models.

Highlights

  • Sediment transport is the main process that drives the morphological evolution of fluvial and coastal environments

  • In SedFoam-2.0, several different viscosity or turbulence closures are implemented, and these models can be selected according to specific flow conditions ranging from laminar to turbulent flows, and in particular, the mixture viscosity can be selected in combination with the granular rheology model for the granular stresses

  • In this subsection the model results are compared with experimental results from Revil-Baudard et al (2015) and Sumer et al (1996) for turbulent sheet flows; the goal of these test cases is to validate the numerical implementation of different turbulence models and to calibrate the free parameter B

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Summary

Introduction

Sediment transport is the main process that drives the morphological evolution of fluvial and coastal environments. Simple parameterization solely on the bed shear stress may be insufficient; for example, the role of pressure gradient in sediment transport has been identified for extreme events such as storms (Foster et al, 2006; Cheng et al, 2017a) Addressing these issues requires the development of comprehensive models that account for the variety of complex hydrodynamics and sediment transport processes on a regional-scale setting (e.g., Lesser et al, 2004; Roelvink et al, 2009). Our final goal is to provide a comprehensive numerical framework that solves the two-phase flow equations in three dimensions with the capability to select different combinations of turbulence and granular stress models for sediment transport applications.

Mathematical formulation
Turbulence-averaged two-phase flow governing equations
Fluid-phase shear stress
Mixture viscosity
Turbulence modeling
Particle-phase stress
Kinetic theory of granular flows
Dense granular-flow rheology
Numerical implementation
Velocity–pressure algorithm
Summary of the solution procedure
Model verification and benchmarking
Pure sedimentation
Laminar bed load
Turbulent sheet flows
Scour at an apron
Findings
Conclusions

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