OpenFAST AeroDyn v15 Convergence Error


I’m using OpenFAST v2.3.0.

I’m having a couple of issues with AeroDyn. I have designed a turbine model around the 15MW reference turbine. I have tuned a controller and I’m running fully aero-elastic simulations in OpenFAST. Each of my simulations are an hour long, there are 22 in total (4-26m/s, 5.5% turbulence at v=15 m/s)

Depending on my exact setup, sometimes I get failures on a few of the higher wind-speed simulations, I think due to convergence of AeroDyn. Normally the error messages OpenFAST gives are super helpful, however this one was less so - I have attached the error (error.png). The simulations are stable up until this point with no apparent misbehaviour of the controller.

I read on some of the other posts that people have had issues running AeroDyn when they end up with a negative horizontal local velocity. In the same posts, it was hypothesised that changing the tower potential flow correction between 1,2 can improve things and also increasing the time-step.

What is odd to me is that the error only occurs at node 1 the first blade - I have attached the blade node definition (AeroDynBladeNode.png), the airfoil reference is too a cylindrical section. Given that the solutions are stable otherwise, I think it’s highly unlikely that the fore-aft motion is sufficiently high to cause a negative velocity (it would have to be approximately 20 m/s in magnitude at the tower top).

Any thoughts would be greatly appreciated :slight_smile:


Dear Sam,

I asked Andy Platt, and here is his response:

Does upgrading to OpenFAST v2.4 solve the problem?

Best regards,

Hi Jason,

Thanks very much for getting back to me. It looks like Andrew found this error when using the 15MW IEA airfoils. When I tuned my model based on a different set of airfoils, the problem went away but I’ll try Andrew’s fix anyway.