Submitted to: Transactions of the ASABE
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/10/2011
Publication Date: 4/20/2011
Citation: Sauer, T.J., Hatfield, J.L., Haan, F.L. 2011. A wind tunnel study of air flow near model swine confinement buildings. Transactions of the ASABE. 54:643-652. Interpretive Summary: Facilities that feed livestock are sources of odor, dust, and greenhouse gases. The amount of these materials tranported and how far they are transported are determined by management practices and environmental conditions. In this study, we used a wind tunnel with scale models of swine production buildings to study the effect of wind speed and direction on air flow near the buildings. The results showed that when buildings are placed across the wind, the building creates a large area behind it with low wind speed. The sloping roof of the building also helps make the low wind zone about 5 times taller than the building. When the wind blows along the same direction as a building, the area of low wind speed is much smaller. These results indicate that if buildings are built across the direction of the prevailing winds, there is a greater chance that a sheltered zone will form behind the building that may reduce the amount of odor, dust, and greenhouse gases transferred from the site. This research is important to other scientists and producers looking for ways to reduce air quality impacts from agricultural practices.
Technical Abstract: One of the most significant and persistent environmental concerns regarding swine production is the transport of odor constituents, trace gases, and particulates from animal production and manure storage facilities. The objectives of this study were to determine how swine housing unit orientation affects air velocity and turbulence downstream and to assess the opportunities for reducing offsite transport of air quality constituents. Measurements were made with ~1:300 models of swine finisher buildings in a low-speed wind tunnel capable of producing air velocities up to 12 m s-1 (27 mph). Runs were completed with no building models and with 1 housing unit oriented parallel and perpendicular to air flow and with 4 housing units oriented parallel, perpendicular, and at a 30° angle to air flow. Velocity and turbulence measurements were completed in a grid of 83 points within a 215 mm-high x 400 mm-wide vertical plane (8.5 x 15.7”) at separation distances 2H, 5H, and 10H downstream from the building model arrays (H = model height of 17.5 mm) using a constant temperature anemometer system with a 3-D hot film probe. A large zone of reduced longitudinal velocity (u) and increased turbulence intensity (Iu) in the wake of model buildings oriented perpendicular to flow was observed and was still pronounced 10H downstream. The size and strength of this turbulent wake is attributed to the sloping roofs of the building models which, with a frontal vortex under the upwind building eave, initiate and sustain a vertical jet and boundary layer detachment. One or 4 parallel building models exhibited the least influence on downstream velocities and turbulence intensities. One perpendicular and 4 30° models produced intermediate effects. Careful interpretation of these results is necessary to assess the potentially offsetting effects of reduced velocity and increased turbulence of the wake zone and applicability to field conditions with variable wind speed and direction and atmospheric stability.