Multiple solutions in a building with four openings ventilated by combined forces

Abstract

Ever since the existence of two stable ventilation solutions in a two-opening building was identified, questions have been asked whether multiple solutions of natural ventilation exist in complex buildings and what are the physical mechanisms that can lead to the existence of multiple solutions in complex buildings. We examined a simple one-zone building with four openings using the simple macroscopic method of thermofluid modelling by assuming that the air temperature in the building was uniform. A conventional network modelling computer program was used to simulate the four-opening building ventilated by combined buoyancy and wind forces. The ventilation flow rate in the simple four-opening building was found to be a linear superimposition of that in two corresponding two-opening buildings with opposing and assisting winds respectively. We have shown that when the ventilation flow in the two-opening building with opposing wind is sufficiently strong, two stable solutions and one unstable solution can exist in the corresponding four-opening building. There is a good agreement between the ventilation flow rates predicted by the network modelling method and our simple analytical solutions. The findings suggest the possible existence of multiple solutions in complex building configurations. © 2005 Sage Publications.