## 5 Discussion  
### Preliminary Results and Mesh Sensitivity Analysis  
Regarding mesh sensitivity, the analysis performed in the preliminary results of the interFoam solver did not reach mesh independence for pressure near the stagnation point, and the values of the pressure obtained were higher than those of the experimental ones. This fact can lead to the conclusion that the interfacial VoF model cannot reproduce the diffusion caused by the shear stress inside the plunge pool due to the impossibility of the simulated fluids changing energy between them. On the other side, the Euler-Euler model has one set of equations for each fluid and is more capable of simulating the energy changes between the fluid phases. Looking for the variation of the mean dynamic pressure as a function of the cell size, it is possible to verify that the values obtained by the interFoam solver increase with every new refinement, and no diffusion in the jet is simulated. On the other hand, because this model does not have mesh independence, the value of the mean dynamic pressure can be closer to the experimental ones for coarser meshes with cell dimensions that cannot describe the flow patterns correctly. By opposition, the Euler-Euler solver tends to a constant value of the mean dynamic pressure as the cell size is reduced. The obtained values also fit the experimental data. Outside of the jet footprint, both solvers reach mesh independence, but in the same way, the solver that better matches the experimental data is the Euler-Euler one. The interfacial VoF model continues to overestimate the pressures due to the inefficient jet diffusion. A good compromise between computation time and results quality is achieved with the D24 mesh at the stagnation zone. Similar findings were reported by [PERSON] et al. [42] and [PERSON] et al. [23], who concluded that an optimal trade-off between mesh resolution and simulation accuracy could be achieved with comparable mesh densities. Furthermore, [PERSON] et al. [17] noted that mesh independence was only achieved with the twoPhaseEulerFoam solver. Regarding time consumption, D36 mesh leads to simulations taking eight times more time than the simulation with twenty-four cells in the jet diameter. The flow velocity inside the plunge pool leads to mesh independence in both numerical approaches. The simulated core lengths exceed the experimental measurements by more than threefold. Furthermore, the core penetration observed in the simulations was significantly higher than that in [PERSON]'s data, with experimental results indicating a core penetration of approximately \(3.5D_{i}\). Like the mean dynamic pressure, the initial jet turbulence conditions strongly influence the velocity field at this stage of the preliminary tests. This variable has not yet been calibrated; due to that, the velocity values are higher than the experimental ones. In terms of the air concentration inside the plunge pool, the twoPhaseEulerFoam solver showed minimal mesh dependency, while interFoam results varied significantly, with air concentration values ranging from 0.5 to 0.0 when comparing the D6 results to those from other finer meshes. This is one of the significant limitations of the interfacial VoF model. The simulation of water droplets when simulating a free-water jet is related to the cell size due to changes in these variables, leading to significant differences in air concentration values [23; 27]. InterFoam solver is more capable of simulating separated flows due to the inability to simulate fluid mixing. The fluid mixture is simulated in this model due to numerical diffusion, which can be notable in meshes with lower cell resolutions. On the other side, we have the Euler-Euler model, where two distinct fluid phases are calculated, and the mixing between them can be modeled. The following main conclusions were drawn from this analysis:  
* Pressure and air concentration: TwoPhaseEulerFoam accurately reproduces stagnation point pressures and air concentrations.