3D numerical investigation of poultry farms pollutant emissions over complex terrains

Abstract

Wind mapping is of utmost importance in various environmental engineering applications concerning pollution dispersion. The available wind atlases usually provide wind data with low spatial resolution relative to pollution spread mechanisms and usually neglect the effect of topographic features with relatively large or sharp changes in elevation. A benchmark case is studied for computational fluid dynamics (CFD) model evaluation on smooth two-dimensional 2D hill, where the distributions patterns are examined and compared with available measurements obtained from literature. Thereafter, a procedure is introduced to build CFD model of a flyover complex terrain with moderate roughness heights (plants with various height and sparse agricultural building density) initializing from existing topography maps in order to properly extend the predictions over a prototype complex area. CFD simulations are carried out using Reynolds Averaged Navier-Stokes (RANS) equations, to examine two widely used turbulence models on two roughness heights, and spatial discretization models comparing the distributions patterns of the pollutant tracer gas, which has the diffusive action of the NH3.The study shows that CFD simulations can be successfully used in qualifying and quantifying the flow and the dispersion pattern of the pollutant species emitted by several point sources over complex topography consisting of various roughness heights, enabling to map estimations for the flow and mainly for the dispersive-diffusive pollutant structure with high spatial resolution. Additionally, the numerical parameters impact, such as convective and diffusive discretization schemes are also investigated.