Air patterns and turbulence in an experimental livestock building

Air distribution in livestock buildings is important for animal and human comfort. Air turbulence influences the dispersion of air momentum, dust particles and gaseous contaminants. Turbulence models are being developed to predict and study air patterns. Experimental data is beneficial in validating these models. In this study, three-dimensional air velocity characteristics were measured in a full-scale, climate-controlled section of a livestock building with high airflow rate and simulated animal sensible heat. Air jets were produced on both sides of a baffled centre ceiling diffuser and created nearly full, rotary air distribution patterns except for a small secondary circulation at the centre of the room. Cross-sectional fields are presented for probability distributions of air velocity vectors and for various turbulence parameters including microscale lengths. Turbulence time and length scales increased, whereas regularity factor, kinetic energy, energy dissipation and microscale decreased with mean velocity and travel distance of the incoming air jet in the test room. Potential causes of significant transverse vortices measured in the room include assymmetric fan location, and potential assymmetry of the incoming air jet and of heat generation. Distributions of air velocities were non-Gaussian at some positions in the room, especially in the shear boundary layer of the jet and near heat sources. Turbulence in the room airflow seemed isotropic at most positions except in locations in and near the jet, near heat sources and near solid boundaries. (C) 1996 Silsoe Research Institute