In this study a procedure for input uncertainty quantification (UQ) in computational fluid
dynamics (CFD) simulations is proposed. The suggested procedure has been applied to a test case. The
test case concerns the modeling of a heavy gas release into an atmospheric boundary layer over a
barrier. The following uncertain parameters are investigated in their respective intervals: release
velocity (18 m/s, 22 m/s), release temperature (270 K, 310 K) and the atmospheric boundary layer
velocity (3 m/s, 7 m/s). The Stochastic Collocation (SC) method is used to perform the probabilistic
propagation of the uncertain parameters. The uncertainty analysis was performed with two sets of
sampling grids (full and sparse grids) for the uncertain parameters. The results show which of the
selected uncertain parameters have the largest impact on the dispersed gas plume and the local
concentrations in the gas cloud. Additionally, using sparse grids shows potential to reduce the
computational effort of the uncertainty analysis