MULTIPLE STEADY STATES IN A COMBINED BUOYANCY AND WIND DRIVEN NATURAL VENTILATION SYSTEM: NECESSARY CONDITIONS AND INITIAL VALUES

摘要

In this paper, mathematical analyses are applied both graphically and quantitatively to investigate the multiple steady state behaviors of combined buoyancy and wind driven natural ventilation system. Two major issues - the necessary conditions for the multiple steady states to exist and the impact of initial values on the final state of the system - are investigated. The necessary conditions for the system to have multiple steady states are derived for a single space with combined wind and buoyancy driven natural ventilation. Different from previous studies, the derivation comes from the dynamical system characteristics rather than the steady state equations, which can be applied to more general cases. Based on the dynamical system analysis, the quantitative relation between the initial temperature and the final steady state is further revealed for the single variable case. The unstable steady state point is found to be the critical point of the initial value in determining the final (steady) state of the system.