WHAT EXACTLY ARE WIND TUNNELS? WHY ARE THEY IMPORTANT?
While the first “true” wind tunnel wasn’t developed until the early 1900’s, the concept of simulating flight for research purposes actually dates back to the 1700’s. In the early stages of aeronautical research, experimenters discovered the need to replicate the movement of air around an object in order to understand flight. These aeronautical pioneers couldn’t fathom building a flying structure without first understanding lift (the force that directly opposes the weight of an airplane and holds it in the air – think buoyancy) and drag (the force that acts opposite to the direction of motion – think friction or resistance).
The first research efforts consisted of moving a test model through the air at a pre-determined speed to attempt to understand the movement of air (similar to flying a kite). Research quickly transitioned to keeping the test model stationary and pushing air past said object to study the patterns of wind. Early models of the latter research theory consisted of a whirling arm to force air, but researchers quickly learned that this model was not as effective as initially thought and went back to the drawing board.
Back at square one, researchers determined that they could use a propulsion system to create lift and forward motion. Sir George Caley (1773-1857) was one of the first aeronautical pioneers to use an engine to generate this operation via the wings of an airplane¹. This discovery is what helped aeronautical theorists and researchers take flight.
Jumping forward to the end of the nineteenth century, researchers designed the first wind tunnel. This device is composed of an enclosed area in which air is forced through the space using a fan or appropriate drive system¹. Wind tunnels in this day in age are substantially more complicated than the early days, although the same basic principle is still used today.
Springing forward to 2016 – wind tunnels are still being improved upon and built to continue aeronautical research. Steel America (through a local customer/partner) is fabricating a wind tunnel that will be delivered to a leading aeronautical institute of higher education in the United States. There, students will utilize this wind tunnel (along with the others in their extensive laboratory) to study flow visualization over airfoils; lift, drag and movement; as well as propeller performance. This new wind tunnel is an extremely complicated project, but is an exciting project for the Steel America fabrication team.
When the wind tunnel is fully fabricated and assembled, it will be a 35 foot by 107 foot rectangular structure. The current estimated weight (minus the fan/driving system and model support systems) is 77-tons. If you were to stretch the wind tunnel out into one long tube, it would be roughly 250 feet long. One interesting feature about this project is the tunnel’s unique shape. This tunnel has two round-to-square transitions that must be held to exact standards. Dimensional control plays a major key factor in the fabrication of this project. If the tunnel is warped – even the slightest bit – it can (and will) affect the way air moves throughout the structure and will influence the way research is conducted.
The wind tunnel is still in the early stage of fabrication, but it is currently being built in 5 main sections consisting of the following pieces: low speed diffuser, high speed diffuser, contraction unit, fan support, stilling chamber, and four corners. All of the units being fabricated at Steel America will be coated inside and out prior to delivery.
There are many moving parts and players in this project; if all goes according to schedule, the wind tunnel should be delivered and ready for installation at the final site in January 2017.
¹ “Whirling Arms and the First Wind Tunnels.” Last Modified 12 Jun. 2014, https://www.grc.nasa.gov/www/k-12/WindTunnel/history.html