Air entrainment flow field induced by a pool fire,

A laser Doppler velocimeter (LDV) was used in conjunction with a quiescently seeded ambient enclosure to study the mean and transient flow field induced by a 7.1-cm toluene pool fire. Radial and axial mean velocity data are presented in the form of a vector plot to elucidate the flow patterns. A component of the vorticity deduced from the velocity field shows a rapid increase near the maximum location of the visible flame interface. The results show that the mass of air set in motion by the fire is much larger than the mass that is entrained into the visible flame and the vorticity interfaces. The results highlight the need for use of a specific unambiguous definition of entrainment when comparing experimental data and correlations. The probability density functions (pdfs) of radial and axial velocities reveal both outward and inward instantaneous motion of air as well as recirculation. The outward motion is caused by expansion and the inward motion is caused by the vorticity generated by the density gradient. A net inward motion is caused leading to entrainment. The transient measurements are of value to the development of improved understanding and analyses of fire induced flows.