Numerical Simulation of Enclosure Fires with Horizontal Vents

The buoyancy-induced flow generated by a heat source, such as fire in a long square enclosure with single or multiple horizontal vents, has been of interest in the modeling of enclosure fires and heat removal systems for electronic equipment. This flow is studied using numerical methods. A two-dimensional laminar natural convection flow is investigated with the buoyancy term represented by the Boussinesq approximation. The governing equations are solved in the stream function and vorticity formulation using high accuracy finite difference schemes. The effect of single or multiple horizontal vents of different sizes on the induced flow is studied in detail for different Grashof numbers. The results show a significant change in flow behavior for varying vent width at a fixed Grashof number. A bidirectional flow across the vent occurs due to buoyancy, as previously reported in the literature. The results show that the flow becomes more stable with a decrease in the vent width. The critical Grashof number is identified as beyond which the flow becomes unstable, leading to chaotic flow in the partial enclosure. The main focus is on the time-dependent flow, though steady state flow is also obtained at a longer duration of time in most cases. The implications of these results in the modeling of a fire in an enclosed space with horizontal vents are also discussed.