Root effect

Trench effect or gutter effect - a name proposed for the description of the phenomenon, observed and identified for the first time during a fire escalator at Kings Cross London Underground on November 18, 1987. It consists of flame spreading fire Along the inclined level of the trench ("trench"), which is an escalator of moving stairs together with handrails, are prone to "sticking" to flammable bottoms and handrails and creeping up instead of lifting vertically, as may be due to ordinary observations of hot movement gases. This effect, as the stairs and handrails at Kings Cross were made of, among others. wood and other flammable materials, has caused extremely hot heating of these materials to self-ignition temperature and then to a violent explosion. This phenomenon was not known before 1987, and during the investigation into the fire at Kings Cross was not immediately recognized. Thanks to computer simulations, the situation in the London subway has seen an unexpected creeping of flames on the bottom of the ditch (channel, "trench"). Not fully trusting the results of the calculations, a 1: 3 situational model was constructed, which was then set on fire and thus finally confirmed the existence of this phenomenon.

This phenomenon is a combination of two previously known phenomena: the Coanda effect (named after Romanian scientist Henri Marie Coandă's aerospace researcher) and the flashover effect - the rapid firing of fire gases.

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