Nonlinear dynamic analysis of natural ventilation in a two-zone building: Part A - Theoretical analysis

The nonlinear behavior and solution multiplicity of airflow and natural ventilation in multi-zone buildings are significant for building ventilation and smoke control design. A two-zone building with four openings is considered in this study. Nonlinear dynamic behaviors are analyzed, and we report on the fixed points (steady-state solutions) and their stability and provide a description of the bifurcation of the fixed points and an estimation of the separating curve between two stable fixed points. Different flow modes were identified with the same physical and boundary conditions. A multi-zone airflow and thermal coupled program was also used to evaluate the results. There was good agreement between the numerical and theoretical solutions, except that the unsteady-state solutions could not be predicted by the multi-zone program. These results may have significant implications for multi-zone modeling, of natural ventilation and smoke or contaminant spread in buildings, as well as allow its to gain a good understanding of physical flow behavior and solution multiplicity.