Quantification of Source-Level Turbulence during LNG Spills onto a Water Pond

Since the 2004 guidance report by Sandia National Laboratories [1], the use of computational fluid dynamics (CFD) models to simulate LNG vapor dispersion scenarios has been growing steadily, with applications to LNG spills on land as well as on water. Before a CFD model may be applied to predict the vapor dispersion hazard distances for a hypothetical LNG spill scenario, it is necessary for the model to be validated with respect to relevant experimental data. Exponent has performed such validation for the CFD model Fluent, with respect to the Falcon test series [2]. The Falcon test series is unique among all LNG spill experiments because it is the only one in which the effects of obstacles and vapor fences were investigated. Preliminary results [3] from the validation effort proved that mixing and entrainment of gas caused by wind, under the low-wind and stable atmospheric conditions of the Falcon-1 test, are small. By neglecting source-turbulence, it was shown that the wind-induced turbulence did not generate enough mixing to cause the cold vapor cloud to overflow the impoundment [3]. The results indicated that the turbulence generated by the spill and vaporization of LNG dominated the rate of mixing of the evaporated gas with air in the impoundment. The importance of turbulence within the impoundment had previously been recognized by Chan [4], who simulated the Falcon tests using a fixed diffusivity, imposed within and near the fence enclosure.