Harnessing the power of computational fluid dynamics for flow coefficient and rain resistance improvement of Type 1 Natural Ventilators

Type 1 Natural Ventilators act like a shield protecting the building from rain intrusion while allowing air to flow from outside. Despite their wide applications, they are far from the ideal design, mainly due to a lack of data on their air discharge coefficient and rain defense effectiveness under different climatic conditions. According to ventilation standards, since experimental testing of different geometries and configurations of these ventilators are complex, difficult, and costly, this study aims to implement Computational Fluid Dynamics (CFD) tools to investigate their performance. To do this, a combination of 9 various louvre panels was designed with 1, 2, and 3 blades and 5, 10, and 12 cm pitches following type 1 Natural Ventilator design standards. Accordingly, a geometrical model including the louvre panel and the wind tunnel is created, meshed, and tested under different climatic conditions. A mesh independency study and a validation analysis were also done to confirm the validity of the data. The pressure loss and signs of water penetration were monitored while the louvre panel was subjected to an air stream into which water is introduced using an array of nozzles to simulate the wind-blown rain. The results showed that the CFD tool was a strong technique in determining the louvre panels' performance. Accordingly, four categories were defined to separate louvers’ performance in case of their air discharge coefficient and rain defense effectiveness. Namely, category #1 included the 2-blade louvre with 10 and 15 cm pitch and the 3-blade louvre with 15 cm pitch with a relatively high discharge coefficient and rain defense. The result demonstrated that the discharge coefficients of all louvres were not sensitive to wind velocity in the range of 5–10 m/s compared to those in the velocities less than 5 m/s and higher than 10 m/s. In addition, the discharge coefficient decreases dramatically as the number of blades over the pitch ratio increases. Finally, according to the results of this study, it was understood that the choice of a louvre configuration is application specific; for instance for applications in which high airflow is the dominant requirement, louvres configuration in category 3, efficient for airflow only, are the best choices.