How do odour plumes exit tunnel ventilated meat chicken sheds-considerations of thermal buoyancy and plume interception structures?

Abstract

Tunnel ventilated meat chicken (broiler) sheds use ventilation fans to exhaust warm, moist air from the shed, which is also odorous. We've investigated the shape, position and motion of plumes exiting meat chicken sheds using visualisation techniques (smoke) and computational fluid dynamics (CFD) modelling. Our investigations have specifically focussed on the effects of thermal buoyancy on plume rise and the differences in plume movement with one or multiple fans. We've also investigated the effects of using structures such as interception walls (otherwise referred to as windbreak walls) and short stacks. These structures intercept plumes and direct them vertically to accelerate dilution; however results show that interception walls and short stacks have only a short-range (~150 m) effect on odour plumes, and presumably odour impacts under stable atmospheric conditions. We have found that poultry shed exhaust plumes tend to be buoyant and rise; and that the mechanical force imparted on exhaust plumes by ventilation fans is limited to a relatively short distance from the fans. Results from this research will enable dispersion modellers to refine the way they define the complex origin/source of odour plumes from meat chicken sheds.