The theoretical foundations and potential for large-eddy simulation (LES) in fluvial geomorphic and sedimentological research

Large-eddy simulation (LES) is a method for resolving the time-dependent structure of high Reynolds number, turbulent flows. With LES it is possible to model and track the behaviour of coherent turbulent structures and study their effect on the flow field. Hence, LES is potentially an important research tool in the fluvial sciences where flow mixing, sediment entrainment and sediment transport are all affected by the presence of coherent vortices and their interactions with channel boundaries and other flow structures. This paper introduces the LES methodology, discusses a variety of ways for representing small-scale processes within LES (the subgrid-scale modelling problem), and provides some examples of early work into the use of LES in a fluvial context. A number of advances in computational power and numerical methods are required before LES can be effectively applied at the river reach scale. This paper considers some recent developments and their potential for providing validated large-eddy simulations of river flow at the channel scale.