Wind tunnel construction
General Information
A wind tunnel is used to investigate and measure the aerodynamic and aero-acoustic properties of objects.
Probably the best known are the wind tunnel tests of airplanes and cars. While low air resistance and optimum lift values should be achieved for cars, significantly more aspects play a role for aircraft: in addition to the air resistance and lift, there is also sub-surface profile, stability, control etc. Railway trains and ships have also been tested in wind tunnels.
What is important is also the investigation of structures such as high-rise buildings, chimneys and bridges. It must be ensured that these can withstand the wind pressure during storms and especially the wind forces and do not experience critical vibrations alongside natural vibration. To be able to correctly simulate wind current, the entire surrounding area may have to be modelled.
Only on rare occasions can objects be tested in the wind tunnel in their actual size, cars are an exception here, as they are not too big and the relatively low air speeds allow sufficiently large wind channels.
Models
For aircraft or buildings, scale models usually have to be built. One problem, however, is that the air behaves differently with small models to how it behaves with objects in their actual size. By increasing the air pressure and/or reducing the temperature, however, the air properties can be made to fit the scale of the model. In some wind channels, therefore, cold nitrogen is used at -160°C instead of air.
Construction
Wind channels consist of one or more fans which create an air flow, rectifier elements which provide a uniform, non-blasted flow, a nozzle to accelerate the rate of air flow as well as the actual measuring range in which the investigations are carried out. The flow in the measuring distance should therefore be as uniform, parallel, low-turbulence and low-noise as possible.
The turbulence level in the wind channel makes a quantitative statement about the turbulent fluctuation rates. The measuring range can, as shown in the figure, be open, i.e., the flow is blown from the nozzle into a measuring hall and, at the other measuring hall side, it is caught by a receiver or collector, whereby a shear layer builds up between the moving air and stationary air in the measuring hall.
However, there are also closed measuring ranges in which the flow is also led through walls in the measuring range and slotted measuring ranges in which some of these walls have slots.
Principle
Closed recirculating wind tunnel in Goettingen design for the subsonic speed range.
Designs
Also, the air guidance of wind tunnels can be open or closed. Because of the open design, the air is sucked out of the surroundings, flows through the measuring range and escapes at the other end into the open air. Closed air guides are ring-shaped.
Here, the air current captured after the measuring range by the collector and led back to the blower.
Low temperatures and high pressure can only be generated in closed wind tunnels (climatic wind tunnel). Wind tunnels for subsonic speeds can be several metres in diameter, while the size of wind channels for the high supersonic range shrinks to a few centimetres.
In consultation with specialist planners and current specialists, we, as steel constructors, supply you with the entire tunnel tubes with all diffusers, deflection corners, collector and nozzle to laser-measured accuracy. We produce our goods in our own factory and deliver the finished coated tunnel parts to your site. Here, the parts are installed in the building by our experience mounting teams.
You can rely on our many years of experience and have a look at our references.