Open Access Article

Title: CFD modelling of dispersion in neutrally and stably-stratified atmospheric boundary layers: results for Prairie Grass and Thorney Island

Authors: Rachel Batt; Simon Gant; Jean-Marc Lacome; Benjamin Truchot; Harvey Tucker

Addresses: Health and Safety Executive, Harpur Hill, Buxton, SK17 9JN, UK ' Health and Safety Executive, Harpur Hill, Buxton, SK17 9JN, UK ' INERIS, Rue Jacques Taffanel, 60550 Verneuil-en-Halatte, France ' INERIS, Rue Jacques Taffanel, 60550 Verneuil-en-Halatte, France ' Health and Safety Executive, Redgrave Court, Bootle, L20 7HS, UK

Abstract: It is a known problem that CFD models using the standard k - ε turbulence model do not maintain the correct atmospheric boundary layer (ABL) profiles along a flat, unobstructed domain. The present work examines the impact of these errors in the ABL profiles on dispersion model predictions for three field-scale experiments from the Prairie Grass and Thorney Island datasets. The modified ABL profiles produced by the CFD model in the Prairie Grass experiments result in differences in the predicted concentrations of up to a factor of two, as compared to a reference model. For the Thorney Island experiment, the results for the standard k - ε turbulence model are sensitive to the ground surface roughness and problems are identified in relation to the grid resolution near the ground. Industrial risk assessments involving atmospheric dispersion of toxic or flammable substances using CFD models should take into account these limitations of the k - ε turbulence model.

Keywords: CFD; atmospheric boundary layers; ABLs; passive gas; dense gas; dispersion; Prairie Grass; Thorney Island.

DOI: 10.1504/IJEP.2018.093026

International Journal of Environment and Pollution, 2018 Vol.63 No.1/2, pp.1 - 18

Accepted: 16 Nov 2017
Published online: 03 Jul 2018 *