Fire Safety Science Digital Archive

The flow structure of whirlwinds and the near field in the downwind side of a methanol flame was experimentally studied with flow visualization. It is shown that whirlwinds in the downwind side of a flame start from the velocity boundary layer on a floor and flow to the downwind direction extending upwards. Whirlwinds are pairs of alternating counter-rotating periodical vortices. Some origins and formations of whirlwinds are discussed. Moreover, We observed: a V-shaped area, where a cross-wind does not enter inside, in the downwind side of the flame on the floor level; two reverse flows, which flow towards the flame along the inner boundaries of the V-shaped area; and a wall vortex pair which extends from the end of the flame on the floor under the counter-rotating vortex pair within the plume from the flame deflected by a cross-wind. The wall vortex pair was investigated by particle image velocimetry (PIV).