Did I add the files? It’s hard to tell.
Hi Justin – I don’t see that your files attached. Can you upload them somewhere for me to download?
Best regards,
I’m not sure where to upload them, I sent them to jason.jonkman@nrel.gov.
Hi Justin,
I took a quick look at your files and ran a simulation comparing the two. I had to correct a few things in both the FAST v7 and FAST v8 models, as described below, but once I made these corrections, I obtained very similar results between the two models. I’m not sure what you are doing differently such that I needed to correct the files you sent me before they would run, but the changes below resolve the problem.
FAST v7
- The generator DOF was enabled in the FAST v8 model you sent me, but disabled in the FAST v7 model you sent me, so, I disabled the generator DOF in the FAST v7 for consistency.
- You didn’t have the OutFileFmt input parameter needed in FAST v7.02, so, I added that to the FAST v7 primary input file you sent.
- You didn’t send me tower and blade files compatible with FAST v7, so, I modified the tower and blade files you sent me for FAST v8 for compatibility with FAST v7.
- The 2nd tower side-to-side mode shape polynomial coefficients didn’t sum to unity, so, I changed the last coefficient (TwSSM2Sh(6)) to ensure this sum is correct.
- You didn’t send me an AeroDyn file compatible with AeroDyn v13 for FAST v7, so, I took the AeroDyn v14 file you sent me and modified it for compatibility with FAST v7.
FAST v8
- The 2nd tower side-to-side mode shape polynomial coefficients didn’t sum to unity, so, I changed the last coefficient (TwSSM2Sh(6)) to ensure this sum is correct.
I hope that helps.
Best regards,
Jason,
Thank you for taking the time to run those. I apologize for not sending all of the v7 files, they were on my professor’s computer and I didn’t know they were different. The reason why we had the v7 .fst file set to true was because when it was false, it literally didn’t move, 0 power, constant torque, the blades just didn’t move. On the v8 version is still moved- do you know why this would happen?
Dear Justin,
Actually, it was the FAST v8 model you sent me that had the generator DOF disabled (GenDOF = False) and the FAST v7 model had the generator DOF enabled (GenDOF = True). Regardless, I’ve now ran two cases–one case had both models having GenDOF = False and both models produced the same results with the rotor parked. The second case had both models having GenDOF = True and both models produced the same results with the rotor speed accelerating. This is what I would expect to happen.
Best regards,
I am getting weird results. With all the DOFs set to false the results I am getting are not the same.
In version 8, at time t=0 there is one value (for the variables that have values) then at the next timestep there is a different value that continues for the rest of the time.
In version 7 all the values are the same for every timestep, and most of the time they equal the first value that came out of v8. Also, my time starts outputting at .01s and goes to 220.01s in v7 as opposed to 0-220s in v8; I checked Dt_out and everything like that, and they are the same. Could this be something to look at or is that supposed to happen?
Dear Justin,
FAST v8 initializes a bit differently than FAST v7. While it was not possible to output data at time zero in FAST v7, this is possible in FAST v8. The last output step may also be a bit different due to rounding of the time steps. Regardless, I wouldn’t expect either of these to have any influence on the core comparison of the simulation results between the two versions of FAST.
From my test runs with your model, it appears the model converted from FAST v7 to FAST v8 as expected. If you are still seeing unexplainable differences, please clarify what the problem is and how to reproduce it.
Best regards,
Jason,
Thank you for your reply. What I am getting, for this 750 kw model, is 2 different steady-state values for different versions of the same file. Here is a representative sample:
in version 8:
Time RotTorq RootMxc1
0 -1.56E-05 -1.08E-05
.01 4.37 1.27
.02 4.37 1.27
and so on, all the way to Tmax
Version 7:
Time RotTorq RootMxc1
0.01 -1.56E-05 2.96E-06
.02 -1.56E-05 2.96E-06
.03 -1.56E-05 2.96E-06
all the way down.
These are the same files I gave you, but with the right files added and the coefficients fixed.
So what I am doing to run these is this: for v7- put every file in a new separate folder with FAST.exe-one that came standard with a v7 version. I then pulled up command prompt, got to this folder as the directory, typed in ‘FAST NREL750j.fst’ and it ran from there.
for v8-I put all the needed files in a new folder, along with FAST_x64.exe(4/13/16), MAP_x64.dll, and MAP_x64.lib. I then got to the command prompt, made this folder my directory, and typed in FAST_x64 NREL750j.fst and it ran then spit out an out file.
To troubleshoot, both me and my professor ran Test05.fst from the CertTest that came standard with v7 the same way outlined above, and then we converted it using convertfiles.m and ran the now-version 8 test in the same way as above and when we compared those results they were not the same either. They are mostly the same until about 13 seconds and then they completely diverge from each other. For example, the rotor speed on version 7 has a first order decay to zero starting at 13s and the version 8 rpm keeps on increasing.
However, when we look at our 5 mw model that we converted, we do get agreement between 7 and 8 by converting the 7 file into 8 file.
Dear Justin,
For the 750-kW model, what conditions did you impose? Is this the case with GenDOF = True or False, or have you enabled a controller?
For Test05, the test case involves a wind-speed start-up, the generator kicks-in at 6 s, and the generator is lost at 12 s. In FAST v7, the rotor slows down after some time because it has an aerodynamic blade-tip brake that engages when the rotor speed reaches 59 rpm. However, aerodynamic blade-tip brakes have not yet been implemented in FAST v8. Thus, Test05 will differ between FAST v7 and FAST v8 after the deployment of the tip brake in FAST v7. To better compare these cases, you can disable the blade-tip brakes from the FAST v7 model by setting TBDepISp(1) = TBDepISp(2) = TBDepISp(3) to a very high value.
Best regards,
Oh ok, that makes sense about the test05. for the 750 kw model that is with all DOFs set to False.
Dear Justin,
I think I know what you’re doing wrong. When you disable all DOFs in FAST v7, are you inadvertently setting CompAero = False? (CompAero is in the “Feature Flag” section of the FAST v7 primary input file, but CompAero does not really control DOFs.) If so, this is equivalent to disabling AeroDyn, which would be different than what you’ve set in your FAST v8 input file.
I hope that helps.
Best regards,
Jason,
You are right. I know I was checking that for the Test05 version, but I don’t know why I didn’t check that for the 750 model. We have agreement now with the simplest of models, we will begin to add stuff back in until we either find the problems or get matching results with our full model.
Thanks