Comparison of predicted and measured air flow patterns in a mechanically ventilated livestock building without animals

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 5 x 10(4) based on a gap size of 0.1 m and a mean velocity of 6.1 m s(-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. (C) 1997 Silsoe Research Institute.