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为了研究爆炸及燃烧产生的“蘑菇状”烟团的产生机理,在实验室中通过点燃预混过量乙烯和氧气的气泡,产生瞬时燃烧的火球和烟团。纹影法和高速CCD相机直接拍摄法显示瞬时燃烧火球上升时,迅速形成一具有涡环结构的烟团。采用中尺度气象模式RAMS模拟计算相同尺度加热烟团的流动过程。计算机模拟显示产生涡环形状的烟团现象与初始烟团的形状无关,与初始热源温升也无关。浮力涡环产生的机理应是流体的斜压性,即在有重力的条件下浮力的水平差别造成的涡度生成;涡度生成应在轻流体与环境流体相交的侧边界附近。
In order to study the mechanism of “mushroom-like” smoke generation by explosions and combustion, instantaneous fireballs and puffs were created in the laboratory by igniting bubbles of pre-mixed ethylene and oxygen. The smear method and the high-speed CCD camera direct shooting method show that the instantaneous combustion fireball rises rapidly to form a volute with a vortex ring structure. The mesoscale meteorological model RAMS simulation was used to calculate the flow of heated cigarette clusters on the same scale. Computer simulations show that the phenomenon of vortex ring shape is independent of the initial shape of the smoke group, and has nothing to do with the temperature rise of the initial heat source. The mechanism by which a buoyancy vortex ring is generated should be the baroclinism of the fluid, vorticity caused by the difference in level of buoyancy under gravitational conditions; vorticity generation should be near the side boundary where the light and ambient fluids intersect.