The main laser-powder interaction in Laser Powder Bed Fusion (LPBF) manufacturing process happens at the melt pool scale, in the order of 100 micrometer, where liquid metal flow forms as the laser melts the powder. Solid-liquid phase change, evaporation, and surface tension effects drive the melt pool dynamics, which in turn, affects the metallurgical phenomena controlling the quality of the final part. Predictions of the melt pool dynamics are of interest to enhance the understanding of the process and support to the selection of optimized building parameters. They are achieved using high-fidelity thermo-fluid solvers which need to be validated rigorously. The work of Cunningham et al. (2019) provides a comprehensive experimental data set to be used for validation. Using high-speed X-ray imaging, they report the time evolution of the vapor depression depth throughout the static irradiation of a bare Ti6Al4V plate. While many groups try to validate their thermo-fluid solvers against the reported measurements, the simulation results often exhibit earlier onset of the keyhole formation and a higher drilling rate than the experiments. This presentation investigates the sources of the discrepancies by assessing the sensitivity of LPBF thermo-fluid solvers to the modelling assumptions. The main hypotheses examined are 1) the typical choice of the evaporative recoil pressure model proposed by Anisimov, and 2) the selection of a surface tension coefficient linearly dependent on temperature and invariant to surfactant. Preliminary results of the sensitivity of the vapor depression depth obtained with an open-source LPBF thermo-fluid solver, Lethe (https://github.com/chaos-polymtl/lethe), indicate that both modelling assumptions significantly affect the vapor depression onset and drilling rate for realistic variations of the recoil pressure and surface tension parameters. This sensitivity study is currently being extended to a wider range of parameter values to establish the impact of the coupled effects of evaporation, surface tension, and surfactants.