Plume-Dominated Fires Are Driven by Their Own Convection, Wind-Driven Fires by the Wind
Fires fall into two regimes according to which force dominates. In a wind-driven fire the ambient wind overwhelms the fire's own buoyancy: the plume tilts far over, the fire runs downwind in a long narrow shape, and its direction is predictable from the forecast. In a plume-dominated fire the ambient wind is weak relative to the heat being released, so the convection column stands nearly upright, draws air inward from all sides, and the fire's spread direction is governed by its own indrafts rather than by the wind. Plume-dominated fires are the erratic ones: they can spread against the general wind, they intensify as the column strengthens, and if the column collapses the downdraft drives fire outward in unpredictable directions. Weak winds plus an unstable atmosphere favour the plume-dominated regime. The confusion this resolves is expecting every fire to travel downwind. After this Concept you can classify a fire's regime from wind strength and atmospheric stability and say how much its direction can be trusted.
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Fires fall into two regimes according to which force dominates. In a wind-driven fire the ambient wind overwhelms the fire's own buoyancy: the plume tilts far over, the fire runs downwind in a long narrow shape, and its direction is predictable from the forecast. In a plume-dominated fire the ambient wind is weak relative to the heat being released, so the convection column stands nearly upright, draws air inward from all sides, and the fire's spread direction is governed by its own indrafts rather than by the wind. Plume-dominated fires are the erratic ones: they can spread against the general wind, they intensify as the column strengthens, and if the column collapses the downdraft drives fire outward in unpredictable directions. Weak winds plus an unstable atmosphere favour the plume-dominated regime. The confusion this resolves is expecting every fire to travel downwind. After this Concept you can classify a fire's regime from wind strength and atmospheric stability and say how much its direction can be trusted.
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