due to the fact that a very
obvious boundary layer separation occurs in the shaft when the
longitudinal wind velocity reaches a relatively high level.
When using shafts for natural ventilation, the phenomena of
plug-holing and boundary layer separation are hard to be avoided
completely, but the influence induced by them could be diminished
to a large extent. The case with more shafts evenly distributed
on the ceiling will spread the risks and weaken the adverse
effects of plug-holing and boundary layer separation on the natural
ventilation performance globally. Therefore, it is better not to ‘put
all eggs in one basket’.