Hydrogen leakage is a key safety issue for hydrogen energy application. For hydrogen leakage, hydrogen releases with low momentum, hence the development of the leakage jet is dominated by both initial momentum and buoyancy. It is important for a computational code to capture the flow characteristics transiting from momentum-dominated jet to buoyancy dominated plume during leakage. GASFLOW-MPI is a parallel computational fluid dynamics (CFD) code, which is well validated and widely used for hydrogen safety analysis. In this paper, its capability for small scale hydrogen leakage is validated with unintended hydrogen release experiment. In the experiment, pure hydrogen is released into surrounding stagnant air through a jet tube on a honeycomb plate with various Froude numbers (Fr). The flow can be fully momentum-dominated at the beginning, while the influence of buoyancy increases with the Fr decreases along the streamline. Several quantities of interest including velocity along the centerline, radial profiles of the time-averaged H2 mass fraction are obtained to compare with experimental data. The good agreement between the numerical results and the experimental data indicates that GASFLOW-MPI can successfully simulate hydrogen turbulent dispersion driven by both momentum and buoyant force. Different turbulent models i.e. k-