Knowledge of the Nuclear Power Plants (NPPs) containment atmosphere composition in the course of a severe accident is crucial for the effective design and positioning of the hydrogen explosion countermeasures. This composition strongly depends on containment flows which may include turbulent jet mixing in the presence of buoyancy, jet impingement onto the stratified layer, stable stratification layer erosion, steam condensation on the walls of the containment, condensation by emergency spray systems and other processes. Thus, in modelling of containment flows, it is essential to predict correctly these effects. In particular, a proper prediction of the turbulent jet behaviour before it reaches the stably stratified layer is critical for the correct prediction of its mixing and impingement. Accordingly, validation study is presented for free neutral and buoyancy-affected turbulent jets, based on well-known experimental results from the literature. This study allows for the choice of a proper turbulence model to be applied for containment flow simulations. Furthermore, the jet behaviour strongly depends on the issuing geometry. A comparative study of erosion process for the conditions similar to the ones of International Benchmark Exercise (IBE-3) is presented for different jet nozzle shapes.