Now, I'm studying two dof airfoil's flutter,but i don't know how to choose the modal daming coefficient for Isogai wing model! help me please,thank you!

try zero, first. as far as I remember, structural damping is not critical in this case, and is usually very small, anyway. if comparing with somebody else's results (Isogai's) you should know what parameters they used.

Yes, Mani is rigth. Flutter velocity should not depend strcitly on the structural damping (consider if you want a g damping factor of 0.01). Luca

Now,i have another problem,the responce of displacement doesn't converge,as well as attack angle.i use loosely coupled method between cfd solver and csd solver,Could you please tell me what measures should be taken to resolve this problem? it nearly drives me crazy! thank you!!