The main objective of this project is to validate the wake generated behind a wind turbine with Large Eddy Simulation (LES). LES is currently the preferred technique for performing high-fidelity numerical simulations of flows around wind turbines, and is the one used in this work in order to characterise the wake generated by the wind turbine. The cases under study are a surface boundary layer and a single wind turbine case. Several methods are available to simulate the rotor, and actuator disc is the one implemented due to its low computational cost, making it the preferred option for wind turbine wake studies. The actuator disc models the effect of the wind turbine as an external force acting over the area covered by the rotor. A study on three different actuator disc forces is also done: a constant force, a force depending on the undisturbed wind velocity, and a force depending on the integrated velocity directly at the disc. The force chosen to validate the results is the force calculated with the undisturbed wind velocity, since it is proven to provide more real results. Validation is done by comparing the results of the wind turbine wake with those from the reference. Results show good agreement with the reference for low turbulence intensities, but are not reliable for higher turbulence intensities due to the difficulty of arriving to the statistical steady state. The simulations are performed with Alya, the multiphysics simulation HPC code developed at the Barcelona Supercomputing Center. It has been used for wind energy simulations for more than ten years, making it a robust option for wind applications.