Dear Jian,
I’m not sure why you want to simulate turbulence in FAST.Farm without wake meandering, but I agree that using the default spatial coherence parameters will result in unrealistically limited wake meandering.
I’m not sure I understand your “factor of 43”; from what I can tell, you used a factor of 11.6. Regardless, it seems like the result is extremely sensitive to LUlt, so, the original value of LUlt may be the problem.
Best regards,
Dear Jason,
Yes, I agree that I should consider the wake meandering with setting the coherence parameter in three components to be the same. In fact, I considered both cases with and without considering wake meandering and tried to tell the difference between the two simulation methods.
The factor I mentioned above is actually the ultimate load factor in the thesis “Model Development and Loads Analysis of an Offshore Wind Turbine on a Tension Leg Platform, with a Comparison to Other Floating Turbine Concepts” supervised by you. Even though Matha suggests 20 by the sensitivity analysis, I found the failure time (adopting the factor of 43) is much rational. However, the corresponding loading bearing capacity (5,306,200 kN-m) is much larger than the actual value, 458,319kNm, calculated based on the given material and section properties, as listed above.
Therefore, I think some other appendages, such as stiffener, might be used in the real design, even though the current sectional parameters distributed in the report “Definition of a 5MW reference…” could meet the maximum bending moment requirement between the cut-in and cut-out wind speed. It is just my guess, and I might miss something.
Best regards,
Jian
Dear @Jason.Jonkman
Observing the same DEL inspite of different Lult. Please refer to the files here:NREL_Query - Google Drive
I have performed MLife calculations for the same parameter (Tower Base force along wind - TwrBsFx) twice. Once, using the Lult as 48190KN (“NTM_11mps_seed01_twrBaseForce_KN.mlif”) and in the other using Lult as 48190000 N (NTM_11mps_seed01_twrBaseForce_inNewton.mlif). The units of the TwrBsFx for both the cases is in Newtons (“NTM_11mps_seed01_twrBaseForce_inNewton.out”).
I expect to see different results for Short term DEL in both cases. But, the MLife is giving the same result. Could you please help me the issue? Thanks.
Regards,
Kumara
Dear @KumaraRaja.Eedara,
I’m not sure I really understand your question. Just a few comments:
Scale to 0.001.Best regards,
Dear @Jason.Jonkman
Thanks for your response. Sorry to note that the question wasn’t clear to you.
I am intentionally giving the same input file (tower base force along x in Newtons) and running the MLife simulation twice (with out specifying any scaling) using the two settings files. In one settings file, I have given Lult = 48190KN and in the other setting file I have specified Lult = 48190000N. I shall expect different results (since I have not specified the scaling). Right? As you mentioned, that is indeed the case with Goodman correction factors.
But cell “E25” in the spread sheet, that is DEL calculation without Goodman correction is same in both the cases. This should not be the case. Right? Please let me know if I am still not clear.
Regards,
Kumara
Dear @KumaraRaja.Eedara,
I agree with your statement regarding the results when the Goodman correction is applied. I would add that the results with the LUlt specified in kN are not correct because the units are not consistent with the load in N.
For the case without Goodman correction applied, the results should be independent of LUlt because LUlt is only used in the Goodman correction.
Best regards,