solution multiplicity

In a simple single-zone building with two openings under an opposing wind, a macroscopic theoretical analysis of smoke flow direction and smoke mass flow rate is carried out. Three solutions of smoke flow are identified under the same building geometry, the same heat release rate and the same ambient conditions at the steady state. Two of the solutions are shown to be stable and one is unstable. In the two stable solutions, one is an upward smoke flow with an upper smoke layer and a lower air layer, which may be considered relatively safe in terms of smoke control and human evacuation.