ABSTRACT
The behaviour of an air jet that is discharged into a large room at the same temperature has been well studied by I. M. C. Farquharson, D. H. Frean and N. S. Billington, J. T. L. Parkinson and Billington, G. L. Tuve and A. Koestel et al. At the end of the turbulent zone, centre-line velocity diminishes rapidly to less than 0.25 m S-1 and the pattern of air movement is unpredictable, viscous forces being dominant and quite small influences enough to produce random and transient changes. An isothermal jet in free space expands naturally with an included angle of between 20-24°, air being entrained around its periphery, momentum flow conserved and its mean velocity consequently reducing. Adjustable nozzles, of circular cross-section, are often used to supply air to large enclosed spaces such as exhibition halls or arenas.
