Scale model analysis of opening effectiveness for wind-induced natural ventilation openings

摘要

An algorithm is developed to predict the opening effectiveness for wind-induced natural ventilation openings. The method is based on distorted scaling theory with the Buckingham Pi theorem to determine the relationship among the non-dimensional parameters. The non-dimensional parameters chosen were Reynolds number, wind angle of incidence, ratio of height to length of opening and roof slope. Model validation was conducted in a wind tunnel using scale models under isothermal conditions. Types of sidewall opening and covered ridge with sidewall opening for natural ventilation systems in the Taiwan region were employed to compare the opening effectiveness. During the experiments, wind angle of incidence varied from 10 to 90°, wind velocity varied from 1.5 to 4.5 ms{sup}(-1) roof slope varied from 10 to 30°, and ratio of height to length of opening varied from 1/3 to 1. Wind speed and wind angle of incidence were the dominant factors determining opening effectiveness in both types. The covered ridge with sidewall opening proved more effective than the sidewall opening type. This work provides practical information to improve the quality control of microclimate in wind-induced naturally ventilated enclosures.