Comparison of Predicted and Measured Air Flow Patterns in a Mechanically Ventilated Livestock Building without Animals

Abstract Air flow in a section from a full scale livestock building has been simulated using PHOENICS, a computational fluid dynamics program, to give the mean velocity and turbulence energy distribution under isothermal conditions. The section has sloping ceilings, an air intake at the apex, and side-wall extractor fans. A narrow inlet gap creates the horizontal air jet which is the basis of the ventilation system. A summer ventilation rate of 44 air changes per hour was simulated, with a Jet Momentum Number of 0·0076 and an inlet Reynolds Number of 5x10r4 based on a gap size of 0·1 m and a mean velocity of 6·1 m sr-1. Calculated mean air velocites within the section were in close agreement with values measured by a sonic anemometer. Despite its known shortcomings, use of a standard turbulence model to simulate the turbulence energy generation and dissipation gave good predictions of turbulence energy distribution.