Long-term field measurement on effects of wind speed and directional fluctuation on wind-driven cross ventilation in a mock-up building

The purpose of this study is to evaluate the unsteady wind effects on the airflow rates of naturally ventilated buildings. A mock-up was built on the roof of a seven-story building, and was designed to be ventilated with two openings by wind-driven force. The time histories of wind speed and direction, static pressure difference across the two openings, and airflow rate were monitored simultaneously in field measurement. The field measurement was conducted during one year, from June 2010 to May 2011. The pressure coefficient at the openings is significantly influenced by the fluctuating components of the wind speed and direction, and the unsteady airflow rates are also sensitive to the fluctuating components. The differences between the unsteady state airflow rates and the quasi-steady airflow rates are significantly increased when the fluctuating component is larger than the mean component. It can also be seen that if the fluctuating component is larger than the mean component, the quasi-steady airflows model is not applicable to the unsteady airflow rates. A statistical expression for the unsteady wind effects on the unsteady airflow rates is proposed from statistical analysis.

► We evaluate the effects of unsteady wind flow on natural ventilation rate.
► The fluctuation of wind direction is independent of wind speed.
►  Directional fluctuations strongly influence the pressure coefficient.
► The statistical model for prediction of unsteady wind effects is proposed.