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Propagation d'ondes acoustiques dans une suspension de grains mobiles immergés : couplage de modèles discret et continu par la méthode des domaines fictifs

Abstract : When an acoustic wave propagates through a granular medium, it causes the grains to move, usually very slightly. In the same way, the movement of a grain embedded in a fluid matrix generates an acoustic wave. In both cases, acoustic energy is transmitted by the fluid and by the inter-granular contacts. We have developed a new numerical model for simulating wave propagation in submerged granular media that takes into account these two modes of energy transport. For the case of dry granular media, the grains are embedded in air whose inertia is so low that the energy it carries can be neglected. These media can be modeled with "Molecular Dynamics" or related methods. On the contrary, when granular media are submerged in water, the energy carried by the fluid cannot be neglected, rendering their modelization much more difficult. We use the fictitious domain method with distributed Lagrange multipliers to couple the equation of motion of the grains to the wave equation of the fluid. We use finite elements to propagate the wave in the fluid, and the grains are modeled in 2D by rigid, incompressible spheres compatible with the hypotheses of Molecular Dynamics. To validate the model, we perform series of numerical experiments whose results are compared to analytic solutions from acoustics. We also perform a simulation with hundreds of grains under an incident wave to demonstrate the possibilities of the model.
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  • HAL Id : tel-00955389, version 1

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David Imbert. Propagation d'ondes acoustiques dans une suspension de grains mobiles immergés : couplage de modèles discret et continu par la méthode des domaines fictifs. Autre [cond-mat.other]. Université Rennes 1, 2013. Français. ⟨NNT : 2013REN1S109⟩. ⟨tel-00955389⟩

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