AeroDyn v15 convergence issues

Dear Jason
I hope you are doing well.
I have been working on Test #21,the OC4 jacket, for a while and after setting some more output requested parameters in output lists of each module of the FAST v.8 tried to run the code.In the FAST primary input file the computational flags were assigned as follows:
compElast=2,compInflow=1,compAero=2,compServo=1,compHydro=1,compSub=1,compMooring=0,compIce=0.
**The compElast was set to 2 as the purpose of my test is to investigate maximum effects due to external forces implied to the whole structure(piles,Jacket,Tower,RNA and Blades).But when I run the code some warnings due to unsteady airfoils and some errors are occured those I have not been able to get rid of them so far even though I managed to do whatever I thought could have likely related to this.I atteched the errors photos here and if you could help me I would be pleased.
Best regards,
Arsalan Shahmohammadi

Dear Arsalan,

Setting CompElast = 2 will enable BeamDyn, which is not really needed if you are still modeling the NREL 5-MW baseline wind turbine. I suggest setting CompElast = 1 to enable ElastoDyn to model the blade structural dynamics.

Best regards,

Dear Jason
I really appreciate for your quick answer as always.
Sincerely,
Arsalan

Dear Dr. Jonkman,

I am running test13 with the version v8.16 and AeroDyn v15.03. and I am using Turbsim to generate wind velocity time histories for mean wind speed at the range of 4, 6,8 …24m/s and wanna get structural response under these wind speeds. For simplicity, I did no any other changes. However, there seems exist the convergence problem in AeroDyn discussed above, but my problem seems to be more odd.

I almost read all the relevant posts on this forum. I know the adjustment of DT (my DT is 0.005s, so I think this is okay), but I did not change the initial condition as I do not know what better initial rotor speed value should be in this case?

So I think the main problems should lie in the parameters in the AeroDyn input file. I run the test13 with the AFAeroMod=UA and SkewMod=2, for the mean wind speed >14m/s, every time I will get this fatal error below:

Then, By referring to the previous posts, In my simulation, I change the AFAeroMod from UA to Steady model, SkewMod=1. The simulation results are: for the mean wind speed between 4m/s-14m/s, it can run successfully, above 14m/s FAST will give several types of fatal errors, shown in screensnaps below: the Vs, Vy and theta will be minus randomly, and occasionally FAST will give error saying FF wind array boundaries violated.


So with the results above, I would like to seek your suggestions, or do you know any info about how to make FAST work successfully for WP 1.5MW wind turbine. Or you think this convergence problem in AeroDyn v15.03 can not be fixed, the only choose is to using AeroDyn v14 or using the latest OpenFAST?

Looking forwards to your reply!

Best regards,
Charlie

Dear Charlie,

The AeroDyn convergence issues that were common in AeroDyn v15.03 of FAST v8.16 have been resolved in OpenFAST v1.0.0 (or newer), so, you could always upgrade to see if that solves your problem. However, I recall that the convergence issues happened most frequently at low wind speeds with high turbulence, which is not where you are seeing issues.

Otherwise, I see large deflection warnings in your simulation, which I would guess in your case are caused by the use of improper initial conditions. As discussed several times on this forum, it is important to set at a minimum the initial conditions of rotor speed and blade-pitch angle appropriate to each mean wind speed. It doesn’t sound like you’ve calculated/applied these for the WindPACT 1.5-MW turbine (and I don’t have them myself), but the process for calculating them has been discussed on our forum…e.g. here: http://forums.nrel.gov/t/wp-1-5-mw-turbine-pitch-angle/1026/2.

Best regards,

Dear Dr. Jonkman,

Appreciate your assistance. I really do not know so important the initial condition setting would be for FAST! I did the sensitivity analysis for WP 1.5 WM following your given post, now my model can run successfully.

Many thanks!
Charlie

Glad to hear it.

The initial conditions of rotor speed and blade-pitch angle are often important for the controller.

Best regards,