Introduction
Roof top wind driven ventilators are deceptively simple in appearance and are cheap to manufacture and easy to install and costs nothing to operate. But the flow associated with its operation is very complex [1-5]. It accepts air in an axial direction and expels along with the air extracted from inside a building in a vertical direction. The wind driven ventilator is subjected to the vagaries of nature, such as high temperature and rain. While the effects of wind and temperature can be experimentally investigated using conventional wind tunnels, the effect of rain is difficult to ascertain. However, such roof ventilation systems and environmental measuring devices have a problem of moisture ingress, with the potential of system inefficiency or failure in the extreme case. Consequently, the design and development of a new test facility in the form of rain chamber or test section was undertaken. To reduce cost and optimise greater usage of resources, it was decided to make the test facility compatible for operation with a conventional wind tunnel. The availability of such a facility is expected to