Research Fellows Directory
Dr Longhua Hu
Reserach area: combustion physics and flame dynamics in ambient air flows having applications for fire
The flame base drag length of pool fire in cross flows were studied, especially concerning the effect of ambient pressure, by conducting experiments at atmospheric and sub-atmospheric pressures. The combined effects of air flow and pressure were investigated by a series of experiments conducted in a specially built wind tunnel in Lhasa, a city on the Tibetan plateau where the altitude is 3650 m and the local atmospheric pressure condition is naturally low (64 kPa). This is the first work investigating the flame base drag length of pool fires at sub-atmospheric pressure. It was found that flame base drag length is larger at sub-atmospheric pressure and increases with increase in fuel supply rate or cross flow air speed, and decreases with increase in pool size. A new theoretical approach is proposed which accounts for the relation of wind forces with the buoyancy of the flame and the interaction of wind with the total heat release rate from the fire. Three independent dimensionless quantities are introduced: the (inverse) fire source Froude number owing to flame buoyancy, the total buoyancy wind interaction number which can be reduced to a Froude number, and the ratio of fuel vapor density near the surface to the air density. All these pioneer unique efforts contribute a big forward step to advance the understanding of our community on the flame base drag behaviors of pool fire, from commonly in normal pressure condition in the past to a new field of in sub-atmospheric pressure conditions.