Experimental investigation and modelling of a buoyant attached plane jet in a room

Buoyant attached jets are widely used in various types of supply air devices especially in office buildings. This study focuses on a two-dimensional cooled attached jet characteristic, including mean flow field structure, specification of the jet regions and maximum velocity decay. A new superimposing model is derived to predict the maximum velocity decay and validated by measurement results. The measurement results demonstrate that the intermediate region of a buoyant jet does exist when an inner layer extends downstream of the jet slot. In addition, by assuming that the buoyant force is the main extra force on the jet flow in the acceleration process, the superimposing model predicted the maximum velocity decay with precise accuracy in a Reynolds number range of 667–4000, based on slot heights of 20 and 30 mm and slot velocities of 0.50, 1.00 and 2.00 m/s. At a distance of 1000 mm from the slot, the velocity profile displays a self similarity character like an isothermal turbulent jet. In the final region, where the buoyancy flux completely dominates the jet, the jet behaved like a plume with an unstable flow field.