Abstract
Oscillatory convective flows play an important role in fire growth since large-scale turbulence enhances combustion due to surface and bulk mechanisms. The periodic motion of a plume rising from a horizontal line heater was numerically studied using a finite difference method. Calculations showed that a plume above a line heater regularly sways from side to side with frequencies similar to the experimental results by Noto et al. The relationship between the swaying frequency (f__-) and heating rate (Q__-) is expressed as f__-=k__-·Q1/3__-, which is similar to that in a vertical venting study by the author. Heat loss through the walls had a significant effect upon the frequency. Vortices along the plume and a pressure imbalance at both sides of the plume cause the regular swaying motion. In addition, calculations showed that the behavior or the vortices around a turbulent free jet is very similar to that of a plume above a heat source.
