Predicting the Pool Fire Vortex Shedding Frequency

It seems that the most talked-about session at the 1989 ASME Winter Annual Meeting was the open forum titled Some Unanswered Question in Fluid Mechanics (Trefethen and Panton, 1989). The interest in the session was stimulated by the fact that most of these fluid mechanics questions are pivotal also in the field of heat transfer. Indeed, on the first day of the Winter Annual Meeting, several participants to the Panel on Directions and Issues in Heat Transfer: An Agenda argued that the identification and facing of unanswered questions is essential to the process of intellectually revitalizing the field of heat transfer. In this note, the author wants to contribute to this process by facing one of the unanswered questions. It has been known for twenty years that fires pulsate with a regular frequency, releasing large annular vortices (coherent structures) from their bases. What is not known is why f{sup 2} {congruent} 2.3m/s{sup 2}/D describes the shedding frequency of pool-flame oscillation over more than three orders of magnitude of the flame base diameter, from 0.03 to 60 m