Modelling bund overtopping using a shallow water CFD model

This paper describes the development of a model for assessing the hazards arising from liquid spills from storage tanks containing flammable liquids. The model is based on computational fluid dynamics (CFD) solutions to the shallow water equations and is able to account for the interaction of a liquid spill with sloping ground and walls/bunds. These features mean that it has a much wider range of applicability than simple models and yet, as it is based on the solution to the two-dimensional shallow water equations, is relatively quick to run. The key parameter of interest in risk assessments is the fraction of a tank contents that would overtop the surrounding wall/bund that has been designed to retain it. A simple ‘sub-model’ has been developed to take account of this three-dimensional phenomenon within the two-dimensional model. The numerical solution of the shallow water equations is obtained through an adaptive method using two shock-capturing numerical techniques; the weighted average flux (WAF) and random choice methods (RCM). These provide a robust solution algorithm. A simple test case has been used to demonstrate the applicability of the model.