Experimental assessment of the flutter stability of a laminar airfoil in transonic flow

Kurzfassung

First results of a flutter experiment in transonic flow are presented. A wind tunnel model with the laminar CAST 10-2 airfoil was mounted elastically with heave and pitch degrees of freedom in the Transonic Wind Tunnel Goettingen. Laser triangulators and acceleration sensors were used to record the motion of the model. Measurements were taken with free and fixed boundary layer transition in a Mach number range of 0.5 < Ma < 0.85 and for chord Reynolds numbers of 1.0*10^6 < Re < 3.5*10^6. For free transition flutter and limit cycle oscillations occurred both when the degrees of freedom were structurally coupled and when the degrees of freedom were only aerodynamically coupled. However when the boundary layer transition was fixed at 7.5% chord, flutter occured only in the case of structurally coupled degrees of freedom.