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:
“The battle for the mind of Ronald Reagan was like the trench warfare of World War I: never have so many fought so hard for such barren terrain.”
—Peggy Noonan (b. 1950)
“The use of symbols has a certain power of emancipation and exhilaration for all men. We seem to be touched by a wand, which makes us dance and run about happily, like children. We are like persons who come out of a cave or cellar into the open air. This is the effect on us of tropes, fables, oracles, and all poetic forms. Poets are thus liberating gods.”
—Ralph Waldo Emerson (1803–1882)