Review of calculating models of unsteady natural ventilation rate due to wind fluctuations

Natural ventilation is an important form of sustainable building technique that can be used to adjust the indoor environment to ensure indoor thermal comfort and maintain acceptable indoor air quality. Correct estimation of the ventilation rate is a necessary step in natural ventilation design. Natural wind fluctuation and interaction between the wind and buildings determine models of mean flow rate inaccuracy in predicting actual ventilation. In this paper, a summary of calculation models for unsteady natural ventilation is given. Unsteady natural ventilation mechanisms are classified into continuous airflow, pulsating flow, eddy penetration and diffusion phenomena. The theories of different ventilation mechanisms and the differences between various research reports are expounded and discussed. Additionally, an in-situ measurement of the eddy penetration caused by wind turbulence at the opening was conducted to verify the proposed model. The actual application condition of different eddy penetration models is proposed via the comparison between previous models. With respect to the ‘pumping’ mechanism, this is regarded as a special type of eddy penetration for the first time. Research on ‘pumping’ airflow has just started, the mechanism and influencing factors of which will need to be further explored.