Airflow measurements in and around scale model cattle barns in a wind tunnel: Effect of ventilation opening height

Animal houses require an adequate ventilation system to allow for efficient production and, indirectly, high product quality. Indoor air quality is also important in relation to a healthy work and housing environment for both farmer and animal. Furthermore, ventilation is directly linked with emissions of gases with environmental impact, such as ammonia, methane and nitrous oxide. To acquire a better understanding of the complex natural ventilation process in and around animal houses, air velocity measurements were carried out in 1:60 scale models of a dairy cattle house placed in a wind tunnel, using a reference air velocity of 3.5 m s−1. Six different ventilation opening configurations were compared, in order to quantify their effect on internal and leeward air velocity profiles. The different scale model designs clearly gave rise to variable indoor and outdoor air velocities. Enlarging the inlet opening height led to lower velocities near the inlet, while higher velocities were measured at the outlet. The air velocities at the centre of the house were hardly affected by the inlet opening height, even with the front wall completely removed. Removing the outlet wall at the same time, however led to much higher velocities at the centre of the scale model (3–4 times higher). Higher airflow rates were found in scale models with larger ventilation opening surface areas. The presented results additionally provide a useful experimental basis towards validation of Computational Fluid Dynamics (CFD) simulations.

► Ventilation opening heights clearly affect indoor and outdoor air velocities. ► Differences in wind velocities for six designs are presented in a quantitative manner. ► The larger the ventilation openings, the higher the resulting airflow rates. ► The results are useful for the evaluation and improvement of CFD models.