Self coded 1dof pitch code differs from OF's after 1.4s
 

Hi,

I am trying to create my own 6dof code to suit my problem.

I have created a 1dof y translation and it compares very similar to OF's own 6dof solver results.

Now I'm trying to create a similar 1dof pitch rotation. It uses the same algorithm as OF's 6dof solver, using the newmark interpolation scheme.

I found that for this case, the results (force,moment,pitch angle) are very similar up to around t=1.4s. It then starts to show some divergence between the two.

I wonder why this is happening. I checked the code and it follows similar coding to the 1dof y translation, only replacing the translation with the pitching rotation.

Can someone give some hints so to what could have caused the difference?

Thanks.

Update:

I run until around t ~ 3s.

I found that there's some noticeable difference in the orientation of the airfoil. However, even at t = 3s, the difference is not big. Hence, the difference has not diverged. But at the same time instant, the velocities are different.