WIND INDUCED AIRFLOW PATTERNS IN A NATURALLY VENTILATED BARN

Abstract

The airflow patterns in naturally ventilated barns are important for the air velocity that the animals are exposed to under windy conditions. Thus the animal welfare may be affected by the detailed design of the inlets, i.e. shape, size, and position, and their surroundings, i.e. overhang. In order to get more knowledge of the effect of the building design parameters, the air velocities in the occupational zone of a growing finishing pig house were measured in a wind tunnel. A 1/20 scale model of a growing finishing pig house was used for the experiments. The model was placed within the 0.5 m. boundary layer of the wind tunnel. Low (u ref = 3.2 m/s), medium (u ref = 5.5 m/s) and high (u ref = 7.5 m/s) free wind speeds were applied with a corresponding roughness coefficient for the wind profile of n = 0.11, 0.18 and 0.20 for the surroundings. Airflow patterns and air velocities in the scale model were determined for 3 vertical positions of the inlet, 2 roof overhang lengths, and 8 inlet opening heights with the wind perpendicular to the sidewall. The experiments showed that the distance from the ceiling down to the upper edge of the inlets had considerable effect on the air flow patterns in the scale model and thus on the air velocities in the occupational zone. It was furthermore shown that the air velocity in the occupational zone could be estimated by use of relationships between wind velocity and the opening height of the inlet.