Comparative Evaluation of the Cloud Dispersion of a Liquefied Natural Gas Leakage Using the UDM and a CFD Model

Large reserves of natural gas exist worldwide, particularly in areas in which there is no market or where the resources exceed the demand; this natural gas is liquefied for shipping to areas where there is a demand. As the liquefied natural gas is a flammable substance, a leakage in this process may cause undesired events like fires and explosions. The consequence analysis is used to define the extent and nature of effects caused by undesired events and thus to quantify the damage caused by such events. Specific models are used to analyze the spills or jets of gas and liquid, gas dispersion, explosions and fires. The central step in the analysis of consequences is to determine the concentration of the vapor cloud of hazardous substances released into the atmosphere, in space and time. Gaussian and integral tools are extensively used in risk analysis, mainly to develop analysis about gas flow over flat terrain, providing fast dispersion estimations. Recently, with the computational advances, computational fluid dynamics (CFD) tools are used to short and medium range gas dispersion scenarios. However the advantages and disadvantages of each approach according with the scenario evaluated have not been widely discussed. This paper evaluates, using a CFD model, the cloud dispersion of a LNG leakage. Then the results are compared with the results previously obtained by UDM (Unified Dispersion Model) and some advantages and disadvantages of each model are discussed. This study contributes to the decision making about the choice of most appropriated model to evaluate the consequences analysis.