In this paper, the work that has been performed to extend the capabilities of the navis software, a well tested and validated parallel ow solver developed by the research group of CNR-INSEAN, is reported. The solver is based on the nite volume discretization of the unsteady incompressible Navier-Stokes equations; main features include a level set approach to handle free surface ows and a dynamical overlapping grids approach, which allows to deal with bodies in relative motion. The baseline code features a hybrid MPI/OpenMP parallelization, proven to scale when running on order of hundreds of cores (i.e. Tier-1 platforms). However, some issues arise when trying to use this code with the current massively parallel HPC facilities provided in the Tier-0 PRACE context. First of all, it is mandatory to assess an ecient speed-up up to thousands of processors. Other important aspects are related to the pre- and post- processing phases which need to be optimized and, possibly, parallelized. The last one concerns the implementation of MPI-I/O procedures in order to try to accelerate data access and to reduce the number of generated les.