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Title: Air-flow distortion and turbulence statistics near an animal facility

item Prueger, John
item Hatfield, Jerry

Submitted to: Atmospheric Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/30/2007
Publication Date: 8/4/2007
Citation: Prueger, J.H., Eichinger, W.E., Hipps, L.E., Hatfield, J.L., Cooper, D.I. Air-flow distortion and turbulence statistics near an animal facility. Atmospheric Environment. 42:3301-3314.

Interpretive Summary: Air quality problems associated with animal feeding operations are related to the emission and dispersion of gases or particulates downwind of the facility. One of the major problems is that not all facilities behave in the same way and that there is differences observed among facilities about their influence on downwind air quality. This has been assumed to be related to differences in placement of the facility on the landscape and how air moves around a facility. There are few direct measurements of the effect of livestock facilities on the windspeed changes around the building and how these changes in windspeed affect the dynamics of airflow. Detailed measurements were made with fast response anemometers to record the changes in windspeed in three dimensions at several times per second. These observations permit an examination of the effect of buildings on the movement of wind upward and downward of the building. It was observed that as the wind moves over the building the air flow slows down but the movement in the upward direction increases and there is more mixing of the air. These changes allow the air to move quickly and to transport gases and particulates with greater efficiency. These observations will help scientists begin to understand how livestock buildings affect air flow and how they affect air quality downwind of the building site.

Technical Abstract: The emission and dispersion of particulates and gases from confined animal feeding operations (CAFO) at local to regional scales is a current issue in science and society. The transport of particulates in the atmosphere at these scales is largely determined by turbulence. Any models that attempt to simulate the dispersion of particles will specify or assume various statistical properties of the turbulence field. Statistical properties of turbulence are well documented for idealized boundary layers above uniform surfaces. However, an animal production facility is a complex surface with structures that act as bluff bodies that can distort the turbulence intensity in the vicinity of the buildings. As a result, the initial release and subsequent dispersion of effluents in the region near the facility will be affected by the complex nature of the surface. Previous lidar studies of plume dispersion over this facility indicate that plumes move in complex yet organized patterns that would not be explained by the properties of turbulence generally assumed in models. The objective of this study was to characterize the near surface turbulence statistics in the flow field around an array of animal confinement buildings. This was accomplished by erecting three towers in the upwind, within the array and downwind regions of the flow field. Changes in turbulence intensity statistics show substantial effects from the buildings as the wind moves over the site.