Comparison of Odor Dispersion Predictions between CFD Model and CALPUFF Model

摘要

A three-dimensional CFD (Computational Fluid Dynamics) dispersion model was developed to simulate odor dispersion from a 3000-sow farrowing farm. The measured odor emission data were used in the CFD model to predict odor concentrations under 30 meteorological conditions. Atmospheric stability, wind and temperature vertical profiles in atmosphere were configured in the CFD calculation and their effects on odor dispersion were evaluated. A Lagrangian discrete phase model driven by LES (Large Eddy Simulation) turbulent flow field was presented in the CFD model to predict downwind odor concentration. This Eulerian- Lagrangian approach solved for continuous air flow in Eulerian reference frame and then solved for trajectories of discrete odor gas parcels(OGPs) in Lagrangian reference frame. The CFD modeling results were compared with results obtained by CALPUFF model, a Lagrangian puff model recommended by US EPA. The results of both models showed that odor traveled farther under stable condition thanunstable condition with the same wind speed. Under the same atmospheric stability category, odor concentrations at lower wind speed were higher than that at greater wind speed. Stronger odor was favored under stable atmospheric condition at lower wind speed. Odor concentration results predicted by the CFD model were higher than that by CALPUFF model in short distance (< 300 m). CFD predictions were higher than CALPUFF predictions at the longer distance under categories A, B, C, and D, and lower than that under category F. The gaps of odor concentration predictions at the longer distance remained stable and were influenced by atmospheric stability category and wind speed.