CFD-RANS prediction of the dispersion of a hazardous airborne material released during a real accident in an industrial environment

This work presents the Computational Fluid Dynamics (CFD) - Reynolds-Averaged Navier Stokes (RANS) simulation and results of the dispersion of a hazardous airborne material which was released during a real accident in an industrial facility. During the event the material was released as flashing liquid from a point located inside a building, partially opened to the outside. According to estimations, after having evaporated, a total material mass in the order of 900 kg escaped to the atmosphere with a time-varying rate from five main openings of the building. The CFD simulations presented here concern the dispersion of the gaseous substance outside the building from where it was released but inside the complex industrial site. The few meteorological measurements that were available in the area have been used for the construction of inlet flow boundary conditions for the model. To take into account the uncertainty due to the scarcity of the available in situ meteorological data, and the temporal variability of the wind direction, three different incident wind directions have been considered in the computations. In each case, the CFD-RANS results for concentration have been compared with the real measurements recorded by the sensors during the accident, paired in space and time. The performance of the model depends on the incident wind direction and it varies depending on the position of the sensors. However, the overall agreement with the observations is considered as satisfactory taking into account the complexity of the problem and the uncertainties associated with the emission rate and the meteorological conditions. The maximum measured concentrations near the sources are predicted very well by the model.