A study of the characteristics of smoke stratification in lateral point smoke exhaust tunnel

Abstract

In order to study flow stratification behavior in lateral smoke exhaust mode, experiments were carried out in reduced-scale model and numerical simulations model. The characteristics of smoke layer interface, smoke layer thickness, vertical temperature and normalized shear velocity in tunnel with different heat release rates were analyzed. The flow pattern was visualized by a semiconductor laser. The stratification pattern was found to fall into three regimes. Buoyancy, inertia force and suction force, as three factors affecting the flow stratification of smoke, are related by a new dimensionless number. At region I (Frs<2.4), the buoyancy stratification was stable, and there is an obvious interface between the upper smoke layer and the lower cold air layer. At region II (2.4<Frs<4.8), the buoyant flow stratification was stable, but the stratification interface between smoke and cold air was unstable. At region III (Frs>4.8), the stratification becomes unstable, the mixing between smoke and cold air was intense, and there is no obvious stratification interface.