Greetings,
I am trying to assess the noise on a small wind turbine using the aeroacoustics model in OpenFAST (v3.5.1). I am running into multiple problems that I think are related to each other. I would like to discuss the most prominent one.
The SPL output is inconsistent/non-repeatable: I get a different output if I ran the same simulation again, sometimes I get unreasonable numbers, i.e. Infinity. I found that this error emerges from the turbulent inflow noise model. For the TIMod, I used Amiet model, I provided the turbulence intensity in a table, and I calculated Lturb according to Zhu et al. (2005).
I kept OpenFAST main input files and DOFs similar to IEA_LB_RWT inputs.
Here is an example of three different Overall SPL outputs of the same system:
I would like to know the source of this error.
Thank you for your time,
Sheyma
Hello Sheyma,
That’s very puzzling… I am not aware of any randomness in the Amiet model. Can you share the files you’re running? If not, can you share a minimum viable set of files that can help me debug what’s going on? Can you reproduce the error with the IEA_LB_RWT model?
Regards,
Pietro
Hi,
The IEA_LB_RWT model itself doesn’t show this output inconsistency. I was able to figure out the source of error; I was using a TIGrid smaller than the disc area.
You can see this error if you use a grid spacing of 90m with the IEA_LB_RWT model.
To check my understanding of the TIGrid definition, is this how the following grid file should look like?
Total Grid points In Y (lateral), Starts from - radius goes to + radius+
4
Total Grid points In Z (vertical), Starts from bottom tip (hub-radius)
3
Grid spacing In Y (lateral)
40
Grid spacing In Z (vertical)
60
0.1200 0.1200 0.1200 0.1200
0.1100 0.1100 0.1100 0.1100
0.1000 0.1000 0.1000 0.1000
Best,
Sheyma
Hello Sheyma,
I’m sorry about the slow reply. I’ve been looking at this issue and the code is outdated and requires some clean up (it was written a decade ago by some student). This will take me a while. In the meanwhile, I’d recommend to stick to a uniform grid of TI values. My apologies for the delay.
Regards,
Pietro
