NUMERICAL-CALCULATIONS OF UNSTEADY HEAVY GAS DISPERSION

This paper concerns both near-field and far-field numerical prediction s of liquefied gas releases in atmospheric environment. The near-field prediction was related to sudden depressurization of liquefied propan e into atmospheric environment. Three phases of propane vapor, propane droplets, and entrained air were considered, Simplification was made that air and vapor have the same velocity and temperature but differen t volume fractions so that an air-vapor mixture phase could be assumed , and was treated using an Eulerian formulation, The droplet phase was handled using a Lagrangian formulation by which droplet trajectories were computed. A thin-skin evaporation model was used to account for d roplet evaporation for the near-field prediction. Present numerical re sults for the near-held modelling were compared with those obtained wi th a twin-fluid Eulerian-Eulerian model. The far-field prediction was associated with heavy gas dispersion of Burro 8 LNG field test in a fl at terrain. The conventional rc-E eddy viscosity-diffusivity model was modified to account for the anisotropy of turbulence characterized by heavy gas dispersion close to a ground. Numerical results were presen ted for the Burro 8 LNG field test. Results for the far field simulati on were also compared with those obtained with the commercial code DEG ADIS.