INTERACTION BETWEEN WIND-DRIVEN AND BUOYANCY-DRIVEN NATURAL VENTILATION

Ventilation stacks are becoming increasingly common in the design of naturally ventilated buildings. Maintaining a certain airflow direction is crucial for a successful natural ventilation design. This article presents the experimental and theoretical investigation of unsteady wind effects on natural ventilation of a single envelope with multiple openings for wind and buoyancy combined cases. Wind tunnel tests have been carried out to investigate the hysteresis effects, the effects of turbulent wind pressure fluctuations on stack flow rates, and the initial condition effects on the final flow pattern through multiple stacks. It has been confirmed experimentally that when the wind and buoyancy forces are in opposition and nominally equal, the turbulent wind fluctuation could cause effective ventilation rates. When there are only stacks open with a fixed buoyancy force, the flow directions through the stacks depend on the initial conditions; which indicates the uncertainty in CFD simulation due the input of initial conditions.