Trench effect

The grave effect (german trench effect) is a superposition of two well- known but distinct phenomena: the Coandă effect of river dynamics and the flashover from the fire dynamics. The grave effect was discovered in 1988 in the investigation into a fire at the Station King's Cross St. Pancras, in the 1987, 31 people were killed.

Description of the phenomenon

The Coanda Effect is the tendency of a rapidly moving stream of air, to be deflected from a nearby surface. The air flow thereby moves bound to the surface orientation.

The Flashover is a sudden gas ignition of pyrolysis gases, caused by the heating of various materials in a fire. If the proper ratio of stoichiometric gas / oxygen mixture and temperature is, there is a flash jump with pressure increase ( ie a kind of explosion). In this case, all flammable gas ignition surfaces of a room fire spontaneously in flames.

The grave effect occurs when a fire is burning near a steep surface. The flames do not strive as one would expect, to the top but lay down according to the Coandă effect on the surface. The flame fuel the above surface of the fire to such an extent that on the one hand comes to exudation of pyrolysis, on the other hand, the ignition temperature of the surface is achieved. Then it comes in accordance with the flashover theory to a gas ignition, when suddenly the entire slant surface is in flames. The flames shoot out like a flame thrower on the upper end of the inclined plane addition, with enormous temperatures arise. This can lead to light the space above the ceilings.

Gaining knowledge

The grave effect is not yet known very long. When it came in 1987 to the devastating fire at London's King's Cross St. Pancras Underground Station, you could not explain how an initially small fire could lead to an escalator with wooden steps to a sudden flame shock, the above lit the hall and many people cost the lives. A computer simulation showed the previously unknown grave effect, but first saw the programmer as a simulation error. Only different model structures of the escalator could prove that there is a till then unknown shoot-through effect.

Swell

  • Wu, Y. & D. Drysdale, Study of upward flame spread on inclined surfaces HSE contract research report no 122, 1996. ISBN 0-7176-1289-9
  • K. Moodie, The King 's Cross Fire: Damage Assessment and Overview of the Technical Investigation Fire Safety Journal, vol 18 (1992 ) 13-33
  • S. Simcox, N.S. Wilkes & I. P. Jones, a computer simulation of the flow of hot gas from the Fire at King's Cross Underground Station Fire Safety Journal, vol 18 (1992 ) 49-73
  • K. Moodie & S.F. Jagger, Results and analysis from the scale model tests Paper presented at I Mech E seminar, The King 's Cross Underground Fire: fire dynamics and the organization of safety 1 June 1989; ISBN 0-85298-705-6
  • A. F. Roberts, The King 's Cross Fire: a correlation of the eyewitness accounts and results of the scientific investigation Paper presented at I Mech E seminar, The King 's Cross Underground Fire: fire dynamics and the organization of safety 1 June 1989; ISBN 0-85298-705-6
  • Fluid Mechanics
  • Brand doctrine
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