The GOTHIC code was validated using three experiments carried out in the PANDA facility in the framework of the OECD/NEA HYMERES project. These tests addressed the mixing of an initially stratified atmosphere by means of a vertical jet in the presence of on obstacle (circular plate). This paper reports on the simulations of three experiments, and complementary, quasi-steady state tests without stratification, where the flow structure above the impingement plate could be observed by means of PIV velocity measurements in a region larger than that considered in the transient experiments. Moreover, simulations of similar tests without obstacle conducted during the OECD/SETH-2 are also discussed. The reference, best-estimate model used for the analyses of the three experiments with different flow rates and initial and pressure boundary conditions was built on the base of a multi-step approach. This was based on mesh and modelling sensitivity studies mostly performed for the complementary tests, to assess the capability to represent the flow structure produced by the jet-plate interaction with different meshes around the plate. Generally, the results show that the use of a coarse mesh and the standard k-e turbulence model permits a reasonable representation of the erosion process, but with a systematic over prediction of the mixing time.