A SIMPLIFIED TURBULENCE MODEL FOR DESCRIBING AIR-FLOW IN CEILING SLOT-VENTILATED ENCLOSURES

A numerical model was developed to predict flow occurring with opposin g plane-wall ceiling jets representative of slot-ventilated livestock facilities. This model, termed the BETA model, was evaluated by compar ing predicted axial and animal occupied zone (AOZ) velocity distributi ons with a low Reynold's Number turbulence model (LBLR) and a laminar model (LAM). In addition, the BETA model results were compared with ex perimental results from a laboratory-scale test chamber. For opposing plane-wall ceiling jets, the predominant gradient in turbulent viscosi ty was predicted to occur in the vertical direction. An effective visc osity was defined as a function of the inlet Reynold's Number (Re-H) a nd normalized vertical height from the poor. The effective viscosity w as used to selectively augment the laminar viscosity in the Navier-Sto ke's equation. Predicted comparisons between BETA and the LBLR models showed negligible differences for ventilating conditions between Re-H of 35,032 and 11,752. Comparison with experimentally measured axial ve locity decay indicated that the BETA model reproduced ceiling jet deve lopment as well as the LBLR model.