Aeroelasticity
Aeroelasticity is the umbrella term for the physical processes that occur in structures around which flow occurs when aerodynamic loads interact with an elastic structure. The forces exerted can deform solids and possibly cause them to vibrate.
These processes can be observed on the structure of the control and supporting structure of aircraft, on the rotor blades of wind turbines, but also on trees and blades of grass in the wind, on blown reed whistles of the Aeolian harp , the lips of a trumpet player and the vocal cords .
aviation
In aeronautics , a distinction is essentially made between buffeting , flutter , reversal of the rudder effect and aerodynamic divergence .
In spite of the complexity of the physical processes, associated problems are now usually safely mastered. However, with increasing airspeed in the history of aviation , problems with the effects of aeroelasticity, including a sudden crash, have repeatedly occurred. The main problem is the non-linear coupling of the forces caused by the flow with the structural forces.
Wind power
Only the aeroelastic simulation made it possible to build economical, modern wind turbines with an output of several megawatts .
The topic of aeroelastic modeling comes from wind power . The standard IEC 61400 (VDE 0127) provides this procedure as the preferred method for proof of strength .
Bridge building
These processes also occur in bridges whose superstructure is not built aerodynamically. The reason for this may be Kármán vortices ; these are counter-rotating eddies that alternate behind the flowed object. The frequency of this process depends on the wind speed. If this separation frequency coincides with the natural frequency of the object, it starts to vibrate.
The 1940 Tacoma Narrows Bridge fluttered and collapsed. The reason for this was the extremely slim and torsion-free road slab. At higher wind speeds, it was stimulated to torsional vibrations, which overloaded the holding ropes and tore.
Individual evidence
- ^ A b Bernard J. Feldman: What to Say About the Tacoma Narrows Bridge to Your Introductory Physics Class. University of Missouri-St, Louis, St. Louis, MO, February 2003, accessed October 13, 2016 .
- ↑ http://www.sozogaku.com/fkd/en/hfen/HA1000632.pdf
- ↑ https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=18258&context=rtd
- ↑ http://www.ketchum.org/billah/Billah-Scanlan.pdf