Abstract
A mathematical model is proposed to describe the spread rate of a smoke front under an inclined ceiling. The smoke flow is treated as a macroscopic density current, and the effect of buoyancy caused by the inclined ceiling is taken into consideration based on the horizontal spread model.
To substantiate the validity of this model, experiments are also carried out under various conditions. The experimental result shows that with an increase in the inclined angle of the ceiling up to 45 degrees the spread speed of the smoke front increases. However, when the angle exceeds 45 degrees, the spread speed is saturated and it happens that the spread speed slows down on the way of spread. This retardation of the smoke front is caused by the counter flow appeared in the closed space of a model corridor, and does not occur in the open space, which is obtained by taking off the floor. The location of the smoke front is also calculated and the results agree well with the experimental results. Thus, it is confirmed that the present model is valid to predict the spread rate of smoke front under the horizontal and inclined ceiling.
