A Hybrid Turbulence Approach for Simulation of Breaking Waves and Their Impacts on Coastal Structures

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Wave breaking occurs in many coastal and marine environments and is a complex physical process involving moving and overturning free surfaces (i.e. the water/air interface), flow turbulence, air entrainment effects as well as turbulent vortex flow interaction with boundary layers. The effects of wave breaking can be found in many natural and artificial coastal processes and can be hazardous to naval and coastal structures. While the mechanisms for wave breaking have been studied by a number of theoretical and experimental works, numerical modelling of such flow problems is still a challenge. In this project, a new strategy is proposed to simulate the complex turbulent flows involving wave breaking and its interaction with structures. A hybrid turbulence model (i.e. detached eddy simulation) will be incorporated into an existing efficient 3D two-fluid (water/air) free surface capturing code. This involves the extension and application of the hybrid turbulence technique to new areas of turbulence at free surface, a task which has never been attempted so far. The code will be optimised so it can run efficiently on a multiple CPU vector supercomputer. The developed code will be first validated against a number of well documented test cases involving wave breaking on a sloping beach and then will be applied to simulate test cases involving violent impacts of breaking waves due to high amplitude regular incoming waves at vertical and steeply sloping walls. A successful implementation of this technique within the free surface capturing code will enable new insights to be gained in greater detail, in a computaionally cost-effective manner, of turbulent free surface flow problems of practical and physical significance. The proposed research is of current interest to the coastal and marine engineering sectors and relevant to application areas such as a breaking wave overtopping fixed or floating offshore structures, ships and other marine devices.