The road to efficient and accurate design of the optimised coastal defence systems of tomorrow – Coupling numerical models enables complex modelling only where necessary: advantages of each model are preserved without suffering their individual downsides. (Take home message about the coupling strategy in the CREST project) In order to estimate post-overtopping processes such as wave overtopping over the safety line and wave force acting on apartment building, which are most relevant to the coastal safety issues along the Belgian coast, one needs to model multi-scaled physics. Many numerical model have been developed and (partly freely) available in the last few decades to study phenomena related to sea waves and their interaction with coastal defences. Some models are good in wave transformation and applicable to a large domain, while others are more suitable for wave-structure interaction detailing hydrodynamics in time steps but in a limited domain. There is no optimum model which can deal with the multi-scaled physics at the same time. In order to provide a solution for real applications, coupling between numerical models can be employed, which enable to complex modelling in an efficient and accurate way. The excellence of coupling numerical models is that advantages of each model are preserved without suffering their individual downsides. FHR and UGent have been working on the development of the coupling methods in the last years. Figure below shows one example, a coupling DaulSPHysics model and SWASH model. DualSPHysics is a meshfree Smoothed Particles Hydrodynamics (SPH) model and SWASH is a non-hydrostatic model. DualSPHysics can simulate wave-structure interaction in an accurate way while it costs a lot of computational time. SWASH can simulate wave transformation in very efficient way while it cannot deal with complex wave-structure interaction. The coupling of DualSPHysics and SWASH allows modelling both wave transformation and wave-structure interaction and attained a compromise between results accuracy and computational effort. As mentioned above, many coupling methods have been developed for different applications. One can choose one of the methods which is most suitable for one’s problem.
An example of SWASH-DualSPHysics coupling. The calculation is accurate while computational time is reduced in the coupling model.