This Thesis provides a systematic study about the flow past a square cylinder, which is a central field of research in Computational Wind Engineering (CWE). This work consists in compare seven types of mesh changing only the grid quality in order to prove a relationship between the mesh quality and inaccurate solutions on simulation. Fluent is the software used to compute all the results shown in this study. All seven grids are very similar, except on the near region where the boundary layer is present. In addition, all the settings of the model are the same. In this way, the errors that could appear on the solution is only affected by the computational grid.