FAST for inviscid case - problem with RElm

Wind & Water Computer-Aided Engineering Software Tools
1

Hello,

I would like to use FAST for an inviscid case but my polars make an error because some lift coefficients are higher than 3.
Then I tried to delete in all my AeroData files the lines which have these problematic coefficients and I launched the program again.
A new error came:

FAST_InitializeAll:CheckRComp: RElm(17) produces ill-conditioned DR(:slight_smile:

I checked my DR values but they seem to be ok, so I don’t know what makes the problem… The value 17 is my last section. Would you have an idea about what causes that?

Thank you very much in advance.

2

Dear Franck,

I’m not sure I understand your problem with the lift coefficient, but this seams to be unrelated to the problem with RElm and DR. For the latter, see our FAQ: nwtc.nrel.gov/FAQ#Nodes.

Best regards,

3

Thank you for your reply!

The problem is that I checked with my Aerodyn input file and the DRNodes seem to be ok… For a radius of 66 m:

RNodes DRNodes NFoil
2.00 4 1
6.00 4 2
10.00 4 3
14.00 4 4
18.00 4 5
22.00 4 6
26.00 4 7
30.00 4 8
34.00 4 9
38.00 4 10
42.00 4 11
46.00 4 12
50.00 4 13
54.00 4 14
58.00 4 15
62.00 4 16
65.00 2 17

4

Dear Franck,

Your RNodes and DRNodes look correct for the case where HubRad = 0 and TipRad = 66 in the ElastoDyn input file. Are HubRad and TipRad in ElastoDyn also correct?

Best regards,

5

Ah ok I didn’t think about the HubRad. Ok the simulation runs fine now, thank you!