Numerical and experimental assessment of the airflow field and ventilation rates in a naturally ventilated free cubical cattle house with large openings

Abstract

An efficient natural ventilation system in dairy cattle buildings is essential both for animal welfare and for environmental issues since the naturally ventilated livestock buildings are a major source of greenhouse gas emissions. Experimentally it is very difficult to analyse airflow in large ventilated buildings but it can be assessed using modelling techniques such computational fluid dynamics (CFD). The present study is the first step for developing a full 3D numerical model for predicting airflow, indoor climate and greenhouse gas emissions in a large naturally ventilated cattle building. A CFD model was constructed according to the real dimensions of the full-scale building wheras in the experimental part air velocities CO2 concentrations inside the building were measured in various positions, as well as ambient climate conditions. The animal occupied zone (AOZ) was treated as porous media and the resistance coefficient of porous zone was derived by pressure drops across AOZ using a sub-CFD model. Airflow and temperature patterns were presented for a range of external wind velocities. In general the numerical results were in good agreement measured data. These first initial data indicating that CFD can be proven a useful tool for predicting airflow distribution and ventilation rates in large animal buildings and it gave promising results for its use for design optimisation purposes.