Numerical Study of Bund Overtopping after Catastrophic Tank Failures

Gas and petroleum products are stored in a large quantity using tanks. Impoundment systems, such as bund or dike, are put in place to control the spill in case of a failure of primary containments. A catastrophic tank failure, although not likely, can cause an unacceptable consequence as demonstrated in the previous incidents. Nowadays, natural gas is widely used as a feedstock in chemical industry and a fuel to generate power, since it is abundant in terms of reserve and a cleaner energy compared with other fossil fuels. NFPA 59 A specifies the requirements of constructing Liquefied Natural Gas (LNG) storage tanks and dikes, which requires the dike to contain 110% of tank capacity. Previous works using water, liquid nitrogen and LNG have approved that this criteria is insufficient for a dike to contain all the spillage in case of a catastrophic tank failure. Simple correlations were proposed to predict overtopping ratios by regression against experimental data, however, the physical mechanism remains unclear for the behaviors of fluid flow and the interaction of flowing material with dike wall. This work aims to develop a Computational Fluid Dynamics (CFD) model to understand the mechanism of bund overtopping. The model, which will be validated against experimental results, can contribute to conducting a risk assessment of bund overtopping events and provide recommendations for dike design and installation.

Keywords: Tank failtures, Bund ovetopping, CFD, Consequence analysis, LNG