Trisonic wind tunnel

The Trisonic Wind Tunnel (TWT) is a wind tunnel in El Segundo, California. It was built by North American Aviation in the 1950s. This tunnel is so named because it is capable of testing in three speed regimes - subsonic, transonic, and supersonic, with a maximum speed of Mach 3.5.

The TWT is a blow-down type tunnel. In contrast to a continuous wind tunnel, a blow-down wind tunnel only provides air for short period of time. A continuous wind tunnel is driven by large fans and typically is only capable of subsonic speeds. Because a blow-down tunnel can build up pressure over a long period time, it can release air at faster speeds.

The TWT uses two Westinghouse motors (totaling 10,000hp and consuming 8 Megawatts of electricity) that drive two compressors. The compressors build pressure into eight large spheres totalling 214,000 cubic feet. These spheres are connected to a single manifold that connects to a valve mechanism. When the valve is opened, the compressed air passes through the settling chamber, nozzle, and the test section, where instrumented aerodynamic models are mounted. A diffusing area that expands in size slows the air before it is exhausted vertically into the atmosphere.

The speed of the air is determined by the pressure of the spheres and the cross sectional area of the wind tunnel nozzle and diffuser. A smaller cross section in the nozzle causes the air to move faster. The TWT can change the shape of the nozzle by operating a series of hydraulic pistons that bend one-inch thick steel plates into the desired contour.

A distinguishing feature of the TWT is the size of its test section (7-ft x 7-ft). Unlike most blow-down wind tunnels, the TWT test section is a so-called "walk in" test section that can accommodate very large aerodynamic models. Large models have several advantages:

* ability to model relatively small features, such as vortex generators
* ability to instrument the model with more pressure probes and sensors
* more surface area enabling more pressure sensors
* more interior space for instrumentation

History

When Rockwell purchased North American Aviation, it also gained ownership of the TWT. The TWT was gifted to the University of California at Los Angeles (UCLA) in 1998, with the intention of TWT becoming a university research facility. It became known as the Micro Craft Trisonic Wind Tunnel. In 2007, UCLA decided to close TWT, citing environmental issues.

The last test to be conducted at TWT was completed on August 28th, 2007. It was designated as test TWT 807.

References

[http://www.aiaa.org/aerospace/images/articleimages/pdf/comment.may1.pdf] American Institute of Aeronauticsand Astronautics, "Wind tunnels—an endangered species", May 2007

[http://www.youtube.com/watch?v=gflKaMBrG-o] "El Segundo Wind Tunnel", 9/2007

External links