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Accueil > Actualités > Événements > Événements 2016

Opération 31 : Simulation with SPH method of the movement of sea-grass under wave

Auteurs : Philippe Larroude

Waves in the coastal environment are one of the major sediment transport factor. It has been shown that sea grass play an important role in their attenuation, but it is currently difficult to quantify and only few laws exist about wave attenuation by sea grass.
The objective of this work is to try a new approach to simulate the interactions between waves and sea-grass. The chosen method is to simulate waves and plants through SPH (Smoothed Particle Hydrodynamics, SPH). In this model, the plants are defined as a solid that respects Hook’s law, which is in direct interaction with the fluid part. Given the properties of this method especially in terms of computation time, the dimensions of the simulations are limited. A successful representation of the movement of the leaf under waves or/and current by SPH will permit the determination of coefficient of friction corresponding to a type of sea-grass, that can be used in a different larger scale code.

GPUSPH 3D simulation with the real bathymetry of the “pointe de Berre” and with plants at two time under waves

For fluid-structure interaction problems, the structures are usually described by the Lagrangian formulation, while the fluids are often described with an Eulerian formulation. The coupling of the two media is generally obtained using a formulation called ALE (Arbitrary Lagrangian-Eulerian) for the fluid. Various problems have been treated via this formulation, including the study of valve spring (Rugonyi and Bathe, 2001), the interaction of compressible and incompressible fluid with structures (Bathe and Zhang, 2004), or absorption hydro-elastic shock (Le Tallec and Mouro, 2000). In the Lagrangian SPH method, on the other hand, the state of a system is represented by a set of particles, which possess individual material properties and move with the fluid. In the case of large displacement of the fluid-solid interface as well as studies of fluid free surface, it is more convenient to use a Lagrangian formulation for the fluid. Indeed, SPH requires no specific treatment for the free surface (absent surface tension), and can track the two media simultaneously. The SPH method has already produced encouraging results for problems of interaction between fluids (Monaghan et al, 1999) and also between solids (Gray et al, 2001).