Hybrid Model Approaches to Predict Multiscale and Multiphysics Coastal Hydrodynamic and Sediment Transport Processes

摘要

Coastal ocean processes are complicated and they happen as various phenomena that span a vast range of spatial and temporal scales. Since a few decades ago, various geophysical fluid dynamics (GFD) models have been developed for individual coastal ocean phenomena at specific scales. In recent years, computational fluid dynamics (CFD), which can accurately model small-scale and detailed flow structures, has been applied to coastal engineering flows. In view of the multiscale and multiphysics nature of coastal ocean processes, there is a great challenge to simulate them accurately. The challenge comes from model restrictions, numerical techniques, and computer capabilities. The hybrid method (HM) couples different models to each other, and the domain decomposition method (DDM) divides a flow domain into many subdomains, each of which is assigned to an individual model. Combining HM and DDM is one of the most promising currently available techniques to bridge the scales and overcome difficulties in multiphysics/multiscale modeling. This chapter summarizes our recent work in modeling of multiscale and multiphysicshydrodynamics phenomena using HM and DDM. We also discuss related sediment transport, with emphasis on localized scour and erosion processes. First, a hybrid approach that couples the FVCOM and a CFD model is described, and results of multiscale simulation for an effluent thermal discharge from a diffuser at the ocean bottom is presented. Second, an analysis is made of the effects of local-scale hydrodynamics on sediment transport around the diffuser. Third, as a multiphysics modeling of interaction between different phenomena, simulation of flow over sand dunes under action of surface wind is presented to illustrate the interaction between surface waves, currents, and morphology. These examples demonstrate the multiscale/multiphysics methodology.