CFD modelling of livestock odour dispersion over complex terrain, part I: Topographical modelling

Odour from livestock production is an increasing problem in many countries. To reduce odours and establish the effects of livestock production on their surrounding communities, many studies have been carried out on odour dispersion using diffusion simulations and field experiments. Recently, computational fluid dynamics (CFD) has been effectively used to study odour dispersion. CFD can consider various atmospheric phenomena and topographical conditions to study the occurrence of odours and aerosol dispersions. The ultimate objective of this study was to develop an aerodynamic model to qualitatively and quantitatively predict odour dispersion originating from livestock facilities. This first of two papers, deals with the grid construction method, selection of fundamental design criteria and topographical modelling. A mesh model of complex topography, with a 3.6 km diameter and 2.5 km height, was developed with a fine resolution. Well known, commercially available, computational tools were used for the topographical modelling. An earlier wind tunnel experiment contributed to the selection of the grid size (to ensure grid independence), and the selection of time step and turbulence model for CFD simulation. In the second paper, methodologies for modelling of the dispersion phenomenon are presented. In the future, this model will be used to help ameliorate odour conflicts by predicting odour dispersion according to various meteorological and geographical conditions.

Research highlights
► The LES turbulent model was the most appropriate.
► Grid size of 5–10 m was appropriate.
► Time step size of 1–10 s was appropriate.
► Topographical modelling was conducted by CAD, SketchUp, Rhinoceros, GAMBIT, and TGrid.
► The upper boundary was made to be flat to improve the numerical convergence.