To understand the interaction between wave‐breaking induced turbulent coherent structures and suspended sediment transport, we report a Large‐Eddy Simulation (LES) study of wave‐breaking processes over a near‐prototype scale barred beach. The numerical model is implemented using the open‐source CFD toolbox, OpenFOAM^®, in which the incompressible three‐dimensional filtered Navier‐Stokes equations for the water and air phases are solved with a finite volume scheme. A volume of fluid (VOF) method is used to capture the evolution of the water‐air interface. The numerical model is validated with measured free surface elevation, turbulence‐averaged flow velocity, turbulent intensity, and for the first time, the intermittency of breaking wave turbulence. Simulation results confirm that as the obliquely descending eddies (ODEs) approach the bottom, significant bottom shear stress is generated. Remarkably, the collapse of ODEs onto the bed can also cause drastic spatial and temporal changes of dynamic pressure on the bottom. By allowing sediment to be suspended from the bar crest, intermittently high sediment suspension events and their correlation with high turbulence and/or high bottom shear stress events are investigated. The simulated intermittency of sediment suspension is similar to previous field and large wave flume observations. Coherent suspension events account for only 10% of the record but account for about 50% of the sediment load. Model results suggest that about 60%∼70% of coherent bottom stress events are associated with surface‐generated turbulence. Nearly all the coherent sand suspension events are associated with coherent turbulence events due to wave‐breaking turbulence approaching the bed.

This article aims to provide a comprehensive appraisal on the current status of three-dimensional (3D) numerical modeling of local scour around instream hydraulic structures. Many computer models have been developed or are in development to simulate riverbed morphology. Local scour, however, is a special category that requires in general a 3D model based on some averaged/filtered form of the Navier-Stokes (NS) equations and a 3D sediment transport model. Only limited number of 3D scour codes are available for practical usage; there is also a lack of literature on the limitations of the models in capturing the scour-producing flow and the sediment transport solvers embedded within. For 3D local scour modeling, the main intrinsic uncertainty lies primarily in the sediment part. In this article, the basic theory and the state of the art of current 3D local scour models are reviewed, focusing primarily on the sediment solver, and future research needs are discussed.

Investigations of coupled multiphysics processes in rivers and hyporheic zones have extensively used numerical models. Most existing models use a sequential, one‐way coupling between the surface and subsurface domains. Such one‐way coupling potentially introduces error. To overcome this, a fully coupled model, hyporheicFoam, was developed using the open‐source computational platform OpenFOAM. It captures the coupled flow and multicomponent reactive transport processes within both surface and subsurface domains and across their interface. The coupling between two domains is implemented by mapping conservative flux boundary conditions at the interface through an iterative algorithm. Reactive transport is enabled by specifying a reaction network. To start, we have implemented reaction kinetics following the double Monod‐type model with inhibition. The model capability is illustrated through modeling of both conservative and reactive hyporheic flow and transport through dune bedforms. With the novel coupled model, it is now possible to quantify reactions wherein the reactants and products are constantly exchanging between domains and have feedbacks. hyporheicFoam can simulate large, three‐dimensional cases owing to the computational flexibility and power offered by the code structure and parallel design of OpenFOAM.