Dear Readers,
As per my understanding of the fast v7 seismic model, the platform is made very heavy with the stiffness of the base oscillator also set very high. This ensures that the platform experiences negligible deformations due to the motion supplied at the base node. In other words, the platform is made to behave rigidly in a dynamic sense. This ensures that the base node motion is transferred to the tower base with minimum variations.
Assuming my claims are correct in the above para, will it be reasonable to assume that the wave loading I provide in the seismic platform file will eventually be useless? Is the FAST v7 Seismic module coded to interpret wave load effects on the wind turbine? Or is it just best to evaluate the turbine under seismic and wind effects?
Any clarifications shall me. Thanks.
Dear @Kashyap.Subham,
You can model offshore wind turbines with monopile support structures and wave loading with the Seismic version of FAST v7. You will not be able to calculate structural loads within the pile below the seabed (which will be treated rigidly), but you can calculate structural loads within the pile down to the mudline, including the effects of wind, wave, and seismic loading.
Best regards,
Dear Sir,
It seems I do not reasonably understand the computational manipulation in FAST v7 Seismic module. FAST v7 Seismic models the entire tower + foundation in a single unit. When I increase the platform mass, I end up increasing the inertial effect of the platform in the dynamic response which affect the acceleration response for the next time step.
Is it because the member force calculations are based on the structural properties input in the respective input files?
Can you please explain a bit for my understanding?
thanks
subham
Dear @Kashyap.Subham,
I’m sorry, but I’m not really sure I understand your question.
Best regards,
Can you suggest some way to test and confirm whether wave loads are implemented in seismic fast v7?
Also, how is there a way to supress the seismic capabilities and just run a wind + wave analysis using the Fast seismic executable ? I do see an option in the platform input file to flagoff userptfm subroutine. But when I do that and run only with wind and wave the simulation gives me error with supersonic elements. I am using a very small time step already of 0.001 s. Is there something wrong that I am doing within what I have explained above?
Dear @Kashyap.Subham,
To test whether wave loads have been enabled in FAST v7, you could add output parameter WaveElev to the OutList. You should also be able to see the influence of the wave loads on the tower-base loads.
Yes, by disabling the platform DOFs (PtfmSgDOF = PtfmSwDOF = PtfmHvDOF = False) and/or disabling the user-defined platform loading model (UserPtfmLd = 0), the seismic excitation will be eliminated from the system response, even in the seismic version of FAST v7.
Best regards,
Hello dear , i am working on fixed botton wind turbine to check the dynamic behaviour by using TMDI ( tuned mass damper inerter ) under wind and seismic loads ,so can you please guide me regarding this like how to calculate seismic effect under seismic load alone or combined with wind load , please provide me some sketch to hadle simulation procedure ?
thanks best regards
Dear @Muhammad.Irfan,
I suggest reviewing the documentation provided in the Seismic archive of FAST v7 for information on how to define seismic excitation.
You can run simulations with and without aerodynamic loads.
Best regards,
Hello dear jason , i want to know how i can compute mass and stiffness of the wind turbine tower structure based on equation of motion of multi-degree of freedom ( MDOF ) ?
Dear @Muhammad.Irfan,
I’m not sure I understand your question. Are you asking generally or how these are computed within OpenFAST?
Best regards,
exactly , in this equation 𝐌𝐮̈+𝐂𝐮̇ + 𝐊𝐮 = 𝐏(𝑡) , how we can find out M, K , C where now we have
K= [k1 k2,k3,k4 …kn];
M=[m1,m2,m3,m4…mn];
C=[c1,c2,c3,c4…cn] in above equation but i need nmerical values such as M = [2,5,6…N]
Dear @Muhammad.Irfan,
I’m still not sure whether you are asking generally or FAST / OpenFAST specifically.
If you are asking generally, I would recommend reviewing relevant literature.
If you are asking about FAST / OpenFAST, this software will compute the mass and stiffness matrices internally, but the solution is not linear as you show; rather, it includes nonlinearities.
Best regards,
actually, i am talking about within the openfast ,which module has this capability to find out this all this in nonlinear way?
Dear @Muhammad.Irfan,
The ElastoDyn module of OpenFAST solves Newton’s second law (M * udd = F) for the wind turbine (where F = P - K * u-C * ud in your notation), with aerodynamic loads calculated by the AeroDyn module (contributing to F), the generator and controller solved by the ServoDyn module (contributing to F), etc.
Best regards,
ok noted , let me go through it dear , thanks
Mr . jason can you please check this error although i have created extention file ( seismic.dat in place of .fst) but it still saying file does not exit
thanks
Dear @Muhammad.Irfan,
When you call FAST_iwin32.exe, you should specify the name of the FAST v7 primary input file, which in your case is named NRELOffshrBsline5MW_Onshore.fst. The input file you have specified, NRELOffshreBsline5MW_Onshore_Seismic.data, is the input file called by Seismic’s custom UserPtfmLd() routine.
Best regards,
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Mr jason , i adapted this path as you told me ([C:\Users\irfan\Documents\seismic wind turbine\Examples\2_NRELOffshrBsline5MW_Onshore_udm_w_baseline_wo_target> FAST_iwin32.exe
NRELOffshrBsline5MW_Onshore_Seismic.data (rennamed file of NRELOffshrBsline5MW_Onshore.fst] but is giving error that > (Using Seismic file _Seismic.dat
The input file, “_Seismic.dat”, was not found.)
Aborting FAST.
what could be the possible solution ?
is there anythung need to modify before running ?
