Method of quantifying wind-driven natural ventilation flowrate and the development of systematic analysis on the relationship between the flowrate and building configuration

Sheng Wang

doi:10.17918/smnk-r781

It is very challenging to design a building when one is trying to determine the wind-driven ventilation due to the instability of the wind. While a significant amount of research has been carried out to measure and estimate the wind-driven ventilation of buildings in the recent decade, few could systematically quantify the ventilation flowrates in different building types in different wind environments. In order to thoroughly investigate the research gap above, the thesis has been divided into four stages and covered by four related studies. the first stage of the four studies analyzed the relationship between façade opening size and wind-driven airflow rates through small openings by using CFD. Then, for the second stage, a Weibull model fitted wind characteristic study was carried out to try to represent variable wind by a mathematical model. A series of CFD simulation and wind tunnel experiments were conducted for the third stage to establish a methodology to use CFD simulation software carrying out virtual wind tunnel experiments. Finally, for the last stage, by applying the methodology created in the third stage, a series of building façade pressure coefficient simulations were conducted, and wind-driven ventilation of these buildings under historical wind conditions was estimated. To summarize the results of these four related studies, the opening size analysis showed the relationship between the airflow at the building opening, which is driven by the wind, opening size, and wind direction. The investigation revealed the airflow through the opening was mostly driven by the pressure difference, in which wind momentum energy dissipated at the building surface, even while the wind was not perpendicular to the façade. By changing the opening size, it also revealed that the primary driving force of the airflow through opening shifted from pressure to momentum while the opening size was increased. This study provided the threshold of opening size while pressure-driven airflow applied. The next step provided the mathematical model exploration of wind data, which delivered a method to represent wind characteristic data. The study illustrated the inaccuracy of using TMY3 wind data to estimate wind-driven ventilation when comparing to ASOS data. Weibull model fitted into ASOS data showed the potential of using the mathematical model to generate wind data. The thirst step demonstrates the use of a virtual wind tunnel developed to systematically obtain building facade pressure coefficient and the accompanying framework to duplicate this process to fit any building. This virtual wind tunnel analysis was validated against a real wind tunnel experiment (by FIU WoW facility) and the method and framework of acquiring pressure data under different wind conditions via the virtual wind tunnel are expected to generate high-value results for other researchers. Finally, by applying the virtual wind tunnel based data (pressure coefficients), the estimation of wind-driven ventilation rates was calculated for different building and different locations. The calculated flowrates was used in investigating the efficacy and viability of using wind-driven natural ventilation to fulfill current ventilation requirements.

Method of quantifying wind-driven natural ventilation flowrate and the development of systematic analysis on the relationship between the flowrate and building configuration

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Method of quantifying wind-driven natural ventilation flowrate and the development of systematic analysis on the relationship between the flowrate and building configuration

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