The trench effect is a combination of circumstances that can rush a fire up an inclined surface. It depends on two well-understood but separate ideas: the Coandă effect from fluid dynamics and the flashover concept from fire dynamics.
The Coandă effect is the tendency of a fast stream of air to deflect to nearby surfaces. The stream's static pressure tends to decrease, which creates a pressure difference between the wall and areas far from the wall. This bends the stream towards the surface and tends to keep it attached to that surface.
Flashover is a sudden widespread fire, which occurs when most surfaces in a space are heated until they emit flammable gases hot enough to self-ignite. Prior to flashover, flammable gases may be emitted but are too cool to self-ignite.
The trench effect occurs when a fire burns beside a steeply-inclined surface. The flames lie down along the surface, demonstrating the Coandă effect. The flames heat the material farther up: these emit gases that self-ignite, demonstrating flashover theory. The flames from these areas are themselves subject to the Coandă effect and blow a jet of flame up to the end of the inclined surface. This jet continues until the fuel depletes.
Read more about Trench Effect: Background
Famous quotes containing the words trench and/or effect:
“Lord, what a change within us one short hour
Spent in Thy presence will avail to make!”
—Richard Chenevix Trench (1807–1886)
“The second [of Zeno’s arguments about motion] is the one called “Achilles.” This is to the effect that the slowest as it runs will never be caught by the quickest. For the pursuer must first reach the point from which the pursued departed, so that the slower must always be some distance in front.”
—Zeno Of Elea (c. 490–430 B.C.)