Küssner derived an approximate model for an airfoil encountering a sudden step-like change in the transverse gust velocity; or, equivalently, as seen from a frame of reference moving with the airfoil: a sudden change in the angle of attack. The airfoil is modelled as a flat plate in a potential flow, moving with constant horizontal velocity.[2] For this case he derived the impulse response function (known as Küssner function[3]) needed to compute the unsteady lift and moment exerted by the air on the airfoil.
^Bisplinghoff, Ashley and Halfman (1996) pp. 287–288.
References
H.G. Küssner (December 20, 1936), "Zusammenfassender Bericht über den instationären Auftrieb von Flügeln (Summary report on the instationary lift of wings)", Luftfahrtforschung (in German), 13 (12): 410–424
H.G. Küssner (1937), "Flügel- und Leitwerkflattern" (in German)
H.G. Küssner (1940), "Der schwingende Flügel mit aerodynamisch ausgeglichenem Ruder" (in German)
H.G. Küssner (1940), "Allgemeine Tragflächentheorie" (in German)
Ernst H. Hirschel; Horst Prem; Gero Madelung (2004), Aeronautical Research in Germany: From Lilienthal until Today, Springer, p. 287, ISBN978-3-540-40645-7
Tuncer Cebeci (2005), Analysis of Low-speed Unsteady Airfoil Flows, Springer, pp. 15–16 & 52, ISBN0-9668461-8-4
Raymond L. Bisplinghoff; Holt Ashley; Robert L. Halfman (1996), Aeroelasticity (revised ed.), Dover, pp. 281–286, ISBN0-486-69189-6