Numerical Characterization of Natural Swirling Flame Evolving in Free Environment via FDS: a Comprehensive Investigation of Fires Problems

In this paper, a numerical study of a swirling flame generated through the interaction between a central fire and its surrounding fires is performed. A swirling flame can be configured by installing a secondary’s sources surrounding the central source, organized in an asymmetrical manner in order to ensure circumferential entrainment of the central flame by the supply puffs air. An analysis is performed to study this kind of flow. This analysis highlights the different zones that characterize the vertical propagation of a swirling flame; a first zone, close to the fire source, characterized by an acceleration of the flow and an increase of the temperature. A second zone marked by the passage of the temperature by a maximum while changing variation with a net decrease of the flow acceleration and a third zone where the thermal and dynamic fields change and gradually decrease. Moreover, this study shows an axisymmetric flow behavior with two different aspects of its global structure. A central region characterized by a block motion (solid core) where the flow is rotational, characterized by a concentration of vorticity, and surrounded by the rest of the space where the flow is irrotational. Moving vertically away from the active source, results show an attenuation of the axial vortex intensity which is accompanied by a disappearance of movement by block. The centerline evolution of the axial and azimuthal momentum flux enables also to highlight these different aspects of the global flow structure.

Keywords:

Rankine vortex Model , Swirling flame , Momentum flux , Solid core , Swirl number , vorticity