NWTC

Dear Jason, Thank you for the response. I have tried running the same support structure (spar buoy) with FAST 8 at rated wind speed, but I received a strange heave response. Platform_motions_spar_FAST7.png Platform_motions_spar_FAST8.png . I have used the quasi-static mooring system model for both F...

Dear Jason,

I have modeled a spar buoy with an elliptical tower and analyzed it in FAST 7. There is a very large heave response and therefore I want to add a heave plate to mitigate this heave response. Is there a way of including this in FAST 7 in the same way as in FAST 8.16?

Dear Jason,

Thanks for your response, OK I will look into calculating the cross-spectral response.

Hi everybody. I am interested in obtaining the RAOs of a floating wind turbine and I am thinking of using the ratio of the cross-spectral density and the auto-spectral density of input and output signals x(t) and y(t), where the structure has been excited with white noise waves. Can I calculate the ...

Dear Jason, OK, I am thinking that maybe WAMIT and NEMOH work in a different way. To me it seems that when specifying the centre of mass as the actual value in NEMOH, I am also specifying that the structure rotates about this point and thus gives different values of the added mass and damping compar...

Dear Jason, I am running FAST with .1, .3 and .hst-files generated from data obtained with NEMOH. I have a question regarding the location of the centre of gravity used when generating these files. I have used the hywind-spar buoy support structure as my offset so that I can compare my data to that ...

Dear Jason, I followed your post from tue oct 09, 2012 on how to get the mooring stiffness matrix for the hywind spar buoy. By comparing the values from the OC3hywind.bmi file from BModesJJ with the DspCMat (multiplied with -1000), I can see that the last 6x6 part of this 118x6 matrix corresponds to...

Dear Jason,

OK, I see. Thanks a lot again.

Dear Jason,

Thank you. So, if I want to see the influence of the hydrodynamic terms when using BModes, I should use sets of A_11, A_15, A_22, A_24, A_33, A_42, A_44, A_51, A_55 and A_66 from the WAMIT .1-file at different wave frequencies to see the effect on natural frequencies on the total system?

Dear Jason, I want to use Bmodes to get the mode shapes for an elliptical tower cross section mounted on a floating structure. I have obtained the hydrodynamic 6x6 matrix from NEMOH and rewritten the results to the WAMIT-format (.1, .3 and .hst). My plan for getting the mooring stiffness matrix is t...

Dear everybody. I want to get the mooring stiffness matrix of a mooring system design by using MAP++ in Python. I have tried running the example on the online documentation page of MAP++ after installing the mapsys.py module in Python2.7. However, I get the following error message: ================ ...

Dear Jason, Thank you very much for taking your time to respond. I just want to make sure what to set the wave amplitude A to as I am working with NEMOH, which gives exciting force outputs with units. The way I understand your last post, A is set to unity (1,0) in WAMIT and then the significant wave...

Dear Jason. I have an additional question regarding the .3-file from WAMIT. In the user manual, on p. 4-3 it reads that the excitation force is normalized by division with rho*g*A*L^m, where A is the amplitude of the incident-wave. Which amplitude A should be used for the .3-file when FAST should re...

Dear Jason. I have a question regarding the periods used in the WAMIT-files in FAST 8.16. The lowest period is 1,25664 s and the highest period is 125,6 s. Are there som requirements in FAST regarding the minimum and maximum value of the periods? Also, the normalisation in WAMIT is done using rho*L^...

Dear Jason. I am comparing hydrodynamic added mass and damping terms calculated with Nemoh to those provided for the ITI energy barge, which were calculated with WAMIT. I am wondering about the roll, pitch and yaw inertia about the centre of mass inertia about the CM, which in your report "Moda...