燃烧火球浮力涡环实验与数值模拟

Experimental and numerical study of combustion fireball buoyant vortex rings

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RAM S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。

The combustion mechanism for explosive combustion and the flow in the resulting ＂mushroom＂ cloud were analyzed by igniting C2H4 drops in O2. Schlieren photography and high speed videos showed that the fireball immediately forms a vortex ring. A meso-scale meteorological RAMS （regional atmospheric modeling system） model was used to simulate the hot smoke flow. The results demonstrate that the vortex rings are not dependent on either the initial smoke shape or the temperature increase. The buoyant vortex ring forms due to the fluid buoyancy, with vorticity generated in the interfacial region between the light fluid and the environment.