Characterizing the unconfined ceiling jet under steady-state conditions: A reassessment

Detailed velocity and temperature measurements using cross-correlation velocimetry were obtained for unconfined ceiling jets under ceiling transient and steady-state conditions. Small fires of 0.5 to 2.0 kW were produced with a premixed methane-air burner. These measurements represent one of the most detailed studies of unconfined ceil ing jets to date and seem to be in general agreement with large-scale data. Empirical correlations for the steady-state ceiling jet temperature and velocity profiles are described herein. The correlations compare well with, and have improved, results from previ ous works. The maximum temperature may not be scaled as a function of fire-to-ceiling heights for large radial distances. Furthermore, the Gaussian and boundary layer thermal and momentum thi cknesses of the ceil i ng jet are not equal, contrary to the assumptions made in other works.