RANS simulation in complex terrain with the presence of the canopy is a master thesis that deal with the simulations of the RANS equations in a complex and forested terrain. The work has as main goal the analysis of the impact of the main parameters, as mesh refinement,Coriolis effect, buffer effect, presence of the canopy , on the wind main parameter considered, the wind speed, the wind direction and the turbulent kinetic energy. After a first introduction and a presentation of the equations used in the work, the thesis focuses on the simulations, done at the Barcelona Supercomputing Center, using Alya, a simulation code for high performance computational mechanics that solves coupled multiphysics problems using high performance computing techniques for distributed and shared memory supercomputers.