NWTC

Dear Jason, Thank you very much for your time and response! Following your advice, I lowered the glue-code time step while maintaining the controller DLL time step (we didn't know this is possible), lowered the platform-heave damping to 1% critical damping ratio, and removed the platform-yaw damping...

I have a question on the platform DOFs that I'm hoping to get some help on. It's discussed in the SubDyn User Manual that to avoid numerical issue, additional damping in the platform heave DOF may be needed in the HydroDyn input file by specifying the AddBLin(3,3) term which can be calculated by Eq....

Dear Jason, I've done some work since your last reply, but find myself still struggling to interpret the blade deflection profiles. I'm predicting the steady-state performance of a turbine model in OpenFAST. It is built based on an existing model in Bladed. I'm looking at one particular operating po...

Dear Jason, Below is Figure 9-1 found in the report "Definition of a 5-MW Reference Wind Turbine for Offshore System Development". I would like to generate a similar steady-state response plot for a wind turbine that I'm currently modeling in OpenFAST. steady_state.png It was described in ...

Dear Jason, Thank you for your response! For information on ElastoDyn, I'm using this FAST User's Guide ( https://www.nrel.gov/docs/fy06osti/38230.pdf ) which is quite old but I'm not aware of a newer ElastoDyn documentation. On page 10, it was said that "When you request output of motions or l...

Dear Jason, With reference to a previous forum post https://wind.nrel.gov/forum/wind/viewtopic.php?f=3&t=2471 , I'd like to understand how to transform spanwise deflections (for blade #i, strain gauge #j: SpnjTDxbi, SpnjTDybi, SpnjTDzbi, SpnjRDxbi, SpnjRDybi, SpnjRDzbi) from the blade local coor...

Dear Jason, Thank you for your time and response! My thought process of question #4 is, in terms of full-system linearization analysis, if I use an "alternate model" (entire support structure modeled by ElastoDyn) to stay within what's feasible in OpenFAST today, and if I'm not interested ...

In the SubDyn user manual, the guideline for retaining Craig-Bampton modes are: "Until full-system linearization is made available, experience has shown that it is sufficient to enable all C-B modes up to 10 Hz (the natural frequencies of the C-B modes are written to the SubDyn summary file).&q...

Dear Jason,

Thank you for the link to the User Manual!

Upon taking a look at the "PwrCrv.wnd" file used for the "UAE_Upwind_Rigid_WRamp_PwrCurve" r-test, now it's clear to me how I should set up the wind file.

Best regards,
Jing

Dear Jason, I am also looking for ways to create steady, uniform wind files that have either a constant rate of change or staircase-like step changes in the wind speed for an OpenFAST v2.3.0 turbine model. In the "UAE_Upwind_Rigid_WRamp_PwrCurve" r-test, the wind speed ramp is achieved thr...

Hi Jason,

Thank you very much for your response!

Best regards,
Jing

Dear Jason, According to the BModes User Manual (authored by Gunjit S. Bir and dated Sept 2007), for example, ixx_tip is "the side-to-side moment of inertia of the tip mass about the tip section x_T reference axis" (Table 2, pp.12) . My interpretation therefore is that the RNA inertia para...