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Old   March 19, 2014, 18:41
Unhappy Slow Transient Solution
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Hello,

I am doing a 2D transient simulation of an aerofoil passing a cylinder to simulate a wind turbine blade passing a tower using a sliding mesh. At the moment my solution is taking quite a while (over 24 hours).

A problem I am finding is that I have set the maximum iterations per time-step to be 800 and it seems to use up all 800 for nearly every time-step. I was under the impression that after the solution settles down it should only take ~50 iterations. I have set the time step to be the time taken for the mesh to slide the length of the smallest element.

For example I am plotting Cl vs time throughout the solution and I understand that the solution needs to settle (possibly due to limiting it to 800 iterations/time step) but I would assume that after a while.

Any help or advice would be appreciated, I have attached some images of the mesh if that helps.
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File Type: jpg mesh1.jpg (84.8 KB, 12 views)
File Type: jpg mesh2.jpg (97.4 KB, 11 views)
File Type: jpg mesh3.jpg (90.8 KB, 8 views)
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Old   March 21, 2014, 03:19
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Hello scoobysimon,
I'm not expert in airfoil (I've never simulated one), but I'd say that usually in transient simulation the number-it/time-step is less important than the time-step value: I never used such a large number of it/time-step (max 20-30).
I suggest trying 20 it/time-step and reducing the time-step checking your time-discretization.

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