[Nek5000-users] Solution Diverge in the begeninng for NACA0012

[nek5000-users at lists.mcs.anl.gov]

Hi NEKs, 

It has been a long time since I came up with something. 

Here I have a problem and I just would like to know that whether have you experienced it before? 

I am running a simulation of self-sustained pitching of NACA0012 at Re 62000 and at the initial steps itself, the solution diverges due to a rapid increment of velocity at the tip of the trailing edge. 
I compute the torque from elastic axis (which is 18.6% from leading edge) and used equation of motion to compute the mesh velocity to pitch the NACA0012. 

My Moment of Inertia is 0.0014, Stiffness is 0.3 and Damping Coefficient is 0.002. 

In the begeinning of simulation the torq increases rapidly and gradually the mesh velocity increases and collpase. 

I divided the moment by 10 just to see at least my code works. And it worked. But as the moment is divided by 10, I get a less amplitude of pitching . 
So my question is have you experienced like this before? If yes could you please tell me why it because of? 

If not, What can be the reason for a large velocity at the tip of trailing edge? 

NOTE : I have taken air as the fluid so I think the added mass effect is negligible. But do you think is there any possibility of that? 

Any ideas are welcome. 

Thanks 

Sijo GEORGE 
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