*2.2. Discretization*

The geometry discretization was performed by means of ANSYS ICEM CFD. This software allows for the formation of high-quality hexahedral meshes based on the blocking method. Each of the meshes generated for the four scenarios had about one million cells (Figure 4a). The mesh quality was assessed by means of the angle criterion. This criterion takes into account the internal angles of each cell and seeks the maximum internal angle deviation from 90◦ for each element. Figure 4b shows that the mesh quality was above the typical quality criterion for CFDs purposes, which is 18◦. In addition, most of the cell angles were close to the optimum value (90◦).

**Figure 4.** (**a**) Mesh and (**b**) mesh quality in terms of angle criterion.

In addition, a sensibility analysis of the mesh was also carried out. In Figure 5 the effective ventilation distance in front of the number of mesh cells in millions is shown. Three meshes were simulated (0.7 M/1 M/4 M cells) for scenario 2 and 20 m/s at the inlet boundary condition. It can be seen that the effective ventilation distance depends on the number of cells used, but the error committed with each of the meshes is negligible, as opposed to the value of the distance (about 1.5% for the mesh of 0.7 M cells). Nevertheless, in order to minimize the error while maintaining an optimum simulation time, the mesh of 1 million cells was selected for the subsequent experiments. The value for this mesh is near to the convergence value with a deviation of 0.3% (Figure 5), which is an assumable error.

**Figure 5.** Mesh sensibility analysis.
