Measurements of the effect of animals on airflow in an experimental piggery

Airflow and animal activity are important factors influencing the distribution of pollutants in livestock housing. In order to investigate the effects of the animals on commonly measured characteristics of airflow, an ultrasonic anemometer was used to determine air velocities in the occupied zone of an experimental slot-ventilated piggery with near-isothermal, rotary airflow. The determinations were made at eight points at 20 or 40 cm from the floor. Four situations were considered: when the piggery was empty, when it housed unheated models of pigs, and when it housed pigs either in an active or quiet state. Mean air speed and relative turbulence intensities I-t, de fined here as the standard deviation of the local air speed divided by the mean local air speed, were calculated. In the empty building, air speeds around 0.7 m/s were measured at 20 cm and in the range of 0.3-0.6 m/s at 40 cm, ranges of relative turbulence intensities being 0.15-0.19 and 0.07-0.17, respectively. In comparison, in the vicinity of either models or pigs, the average air speeds of 0.3-0.5 m/s were lower (p < 0.05), with I-t values of 0.25-0.54. The results indicate that the occupants of livestock housing affect the airflow around them, and will have substantial effects on the characteristics of airflow in these buildings. This has implications for research carried out in model buildings or empty full-scale buildings. (C) 1999 Silsoe Research Institute.