Dear Sir,
How does OpenFAST distinguish between JONSWAP and PM Spectrum? Setting WaveMode = 2 is common for JONSWAP and PM Spectrum. Is there any other parameter which needs to be adjusted depending on spectrum used?
Dear Akheel,
The JONSWAP spectrum is just a modification of the Pierson-Moskowitz spectrum, based on a peak-shape parameter. Setting WavePkShp = 1 results in the Pierson-Moskowitz spectrum.
Best regards,
Dear Sir,
This is regarding the Jason_PSD.m. I imported the table, coded the time series as ‘Data’ and entered df. then I used the command
[ f, S1 ] = Jason_PSD( Data, df );The results seems to be same as the fft output (A vertical line close to the y-axis). What modifications do I need to make to obtain the one sided PSD with unitm^2/Hz ?
Dear Akheel,
S1 is the one-sided PSD with the units you want. The script is quite simple; open it up and review it for details.
Best regards,
Dear Sir,
Thank you for the quick response.
I did the simulation of load case 5.3. I used the time series in fore aft response in the script Jason_PSD.m expecting that I would get a plot similar to Figure 49 of the report. That I obtained now was a horizontal line (when x and y axis are arranged as in Figure 49). Correct me if my expectation was wrong. Could you please suggest the exact method to obtain the plot if my theory was wrong?
Have you zoomed into the frequency range of interest (likely low frequencies)?
Dear Sir,
Attached is the plot of PSD for different responses. The axis were set same as in the figure 49. What would be the probable reason for mismatch between the plots?
Doc1.docx (3.54 MB)
Dear Akheel,
When you look at the time series of these outputs, do you see the frequency-content that you expect to?
In your PSD plots, what are the units of the x- and y-axes that are plotting? Is the x-axis in Hz? Other than the spike at 0 Hz (corresponding to the mean value of the time series), do you see any nonzero values at higher frequencies?
Best regards,
Dear Sir,
How can I get information about the geometric details of OC3 spar. In fact what I meant is the geometric distribution along the depth of the platform.
Thanks in advance
Dear Akheel,
The external geometry of the OC3-Hywind spar is documented in its specifications report: nrel.gov/docs/fy10osti/47535.pdf. The internal geometry was not specified, so, you’ll have to make your own assumptions for your own purposes if you need that.
Best regards,
Dear Sir,
What I expected was a sectional geometry at different section of the platform just like Table 2.1 of “Definition of a 5-MW Reference Wind Turbine for Offshore System Development”.
Thanks in advance
Dear Akheel,
These details are not available. As I said, the internal geometry was not specified, so, you’ll have to make your own assumptions for your own purposes if you need that.
Best regards,
Dear Sir,
Is it possible to get time series of forces - thrust and moment due to wind on the tower and platform, wave forces on platform - acting on the structure due to wave and wind loads for OC3 Spar using FAST? If yes, In which module do I need to set the output channels?
Thanks in advance
Dear Akheel,
Yes, you can output the applied aerodynamic and hydrodynamic loads in FAST / OpenFAST.
The total integrated hydrodynamic applied loads on the substructure can be output via HydroDyn outputs HydroFxi, etc. See the HydroDyn documentation for more information: drive.google.com/file/d/11WY1LR … sp=sharing.
The total integrated aerodynamic applied loads on the rotor can be output via AeroDyn outputs RtAeroFxh, etc. See the AeroDyn documentation for more information: openfast.readthedocs.io/en/mast … hannel.pdf.
AeroDyn calculates aerodynamic applied loads on the tower, but does not currently calculate aerodynamic applied loads on the substructure. The local aerodynamic applied loads (drag force per unit length) on the tower can be output via AeroDyn outputs TwNβFdx and TwNβFdy for tower node TwNβ. The total integrated aerodynamic applied loads on the tower are not currently output.
Best regards,
Dear Sir,
This message is regarding aerodynamic force calculation on tower. Does it make huge difference if I summate the aerodynamic loads on tower node from that with integrated force?
Dear Akheel,
I’m sorry, but I don’t really understand your question.
Best regards,
Dear Sir,
I was asking that if I summate the aerodynamic force at all tower node, Will I get the total (integrated) aerodynamic force acting on the tower?
Dear Akheel,
Yes, that is correct. Please be aware though that AeroDyn outputs the tower aerodynamic applied loads as force per unit length. So, you’ll need to integrate (e.g., multiple by the tower element lengths) to get the total aerodynamic force applied on the tower.
Best regards,
Dear Sir,
I have run a case with TwrNβFdx with β ranging from 1 to 9. but the output corresponding to these variable were obtained as zero. Can you comment on this?
Sincerely,
Akheel kk
Dear Akheel,
Do you have tower aerodynamic loads enabled (TwrAero = TRUE)?
Do you have tower output nodes identified via NTwOuts and TwOutNd?
Best regards,