The intensive use of immersed granular flows has motivated a large amount of work in this field of research. We present here a new numerical model to represent accurately and efficiently mixtures of fluid with grains. On one hand, the motion of the grains is solved at the grain scale by a contact dynamics method that consider grains as discrete elements. On the other hand, the fluid flow is computed from a continuous model of the mixture at a greater scale. The link between the two scales is

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... vided by an interaction force based on the Darcy's law for porous media and used as a closure relation in the equations of the model. Some results of simulations in a two dimensional space are provided to prove the efficiency of the implementation.