Experimental study on natural ventilation performance of a two-sided wind catcher

Abstract

Experimental wind tunnel and smoke visualization testing was conducted to investigate the performance of a two-sided wind catcher. This type of wind catcher is divided internally into two halves for the purposes of air supply and extract. In this study, the two-sided wind catcher model was constructed of two similar one-sided wind catcher models, which were attached back to back. These one-sided models are 1: 40 scale models of Kharmani's School wind catcher in the city of Yazd. Experimental investigations were carried out using an open-circuit wind tunnel, and both the induced volumetric airflow into the building and the pressure coefficients around all surfaces of the wind catcher model were measured at various wind angles. Additional experimental tests and computational fluid dynamics simulation of the wind catcher in the wind tunnel were also conducted in order to assess the accuracy of measurement procedures and the uncertainty of experimental results. To evaluate the stack effects on the natural ventilation performance of a two-sided wind catcher system, the results were compared to the corresponding results of a one-sided one. As a result of placing urban full-scale wind catchers in the boundary layer of atmospheric winds, the effect of this phenomenon was also examined experimentally. The experiments were performed when the wind catcher model with an adjoining house was placed in the wake of upstream objects, resembling neighbouring buildings. It was found that for an isolated two-sided wind catcher model, maximum efficiency is achieved at an air incident angle of 90°, and this can only be explained by the domination of a stack effect rather than dynamic pressure. At this air incident angle the wind catcher efficiency is ≈20 per cent more than the one at zero angle. The results show that the approaching air incident angles, the presence of an object upstream of the structure, and the blowing of atmospheric wind, influence phenomena such as pressure coefficients, induced airflow rate, and the airflow pattern of the two-sided wind catcher. The results show the potential of the two-sided wind catcher as a passive device for providing natural ventilation in buildings.