Special purpose low speed wind tunnels

Low turbulence tunnels: Low intensity turbulence is the prime requirement for many experimental situations. Hence, these tunnels are specifically designed with a wide-angle diffuser just ahead of the test section-settling chamber. The major task of reducing free stream turbulence is done by large settling chamber having honeycombs and the screens. Large contraction ratio of contraction section and several number of screens are some of the important components for this type of tunnel.

Two-dimensional tunnels: These tunnels are intended for testing objects like cylinder, aerofoils etc. These tunnels can be of open or closed types but the main design feature of this tunnel is its height to width ratio of the test section which is more than or equal to 2.

Smoke tunnels: Flow visualization is sole application of smoke tunnels. So, these tunnels are mostly three-dimensional open circuit type tunnels. The source of the smoke source is kept upstream of the test section so as to mix the smoke with free stream before passing over the object of interest. Very high contraction ratio and large number of screens are sometimes preferred for visualization of laminar flow.

Water tunnels: These are the closed circuit type tunnels that are mostly preferred for hydrodynamics application like water flow over immersed bodies. These are preferred for flow visualization studies with particle image velocimetry (PIV) method because it is very simple to implement this technique in water tunnels. These tunnels are comprised of pumps for through circulation of water unlike fans in wind tunnels.