Dear all:

First, my computer is 64-bit.

Then, based on 5MW_OC4Semi_WSt_WavesWN of OpenFAST v2.4, but when running,it says:

FAST_InitializeAll:HydroDyn_Init: Error allocating space for the distributed inertial

forces/moments array.

FAST encountered an error during module initialization.

Simulation error level: FATAL ERROR

Aborting OpenFAST.

I have switched to using the 64-bit OpenFAST executable, openfast_x64_double.exe and ServoData/DISCON_OC3Hywind_x64.dll. And I searched the forum for related issues, but no one encountered a similar situation with me.

So, I come here to ask if someone has face with the same problem and/or knows how to solve it.

Thanks in advanced,

Yicheng

Dear Yicheng,

An error regarding “allocating space” has been discussed before on this forum, e.g., see: http://forums.nrel.gov/t/problems-in-test-in-fast-8/1868/2.

I would expect switching to the standard 64-bit version (not 64-bit with double precision) would solve the problem, unless you simply don’t have enough RAM available on your computer.

Best regards,

Dear Jason,

Thank you very much for your suggestion. When I run the 64-bit version of the software, it can run normally, but when I run the 64-bit with double-precision version, sometimes it runs successfully, sometimes it fails. This makes me a little bit Puzzled.

Best regards,

Dear Yicheng,

The 64-bit version with double precision requires about twice the memory as the 64-bit version with single precision. So, if the double precision version aborts, my guess is you don’t have enough RAM to run it.

Regardless, I generally recommend that you run the single precision version. The single precision version is generally accurate enough and uses double precision variables where it has been deemed to be important.

Best regards,

Dear Jason,

I am working on the 15MW turbine as part of my thesis. I have been editing hydrodyn file variables WaveHs WaveTp and WaveDir. I have also been editing TurbSim.inp file variable URef and creating .bts files. From this I have been running OpenFAST with the corresponding .fst file.

The following error is produced and I am unsure how to fix it, can you help please? Thank very much.

Regards,

Matthew

Dear Matthew,

I would not expect that you’d receive this error solely by changing WaveHs, WaveTp, and WaveDir in HydroDyn or URef in TurbSim.

Regardless, the error appears to be generated by the mesh-mapping routines of OpenFAST because the end points of an element in the HydroDyn module are too close together. The element length may not be exactly zero, but less than a tolerance used in the mesh-mapping routines. Do you have two joints defined very close to (0,0-30) m in your HydroDyn input? Perhaps one joint is set just below the seabed to avoid the computation of buoyancy forces at the bottom of the pile? If so, try moving this joint a bit lower.

Best regards,

Dear Jason,

Thank you for your quick and detailed reply, I really appreciate it!

You make a good point about the two joints close to (0,0,-30). I think that is exactly what is appearing in my HydroDyn Input file, and these values were originally here when I downloaded the files from GitHub. Please see attached image. Bearing in mind this is the 15MW turbine, can you please suggest appropriate values for me to insert for Jointxi , Jointyi , Jointzi ? Thank you kindly.

Best regards,

Matthew

Dear Jason,

I understood what you meant about lowering the joint right after I posted the reply, apologies for that. Good news, it worked! And thank you for that advice.

Unfortunately, I am receiving an error regarding the grid being too small in the z-direction, kindly see the screenshot below. Is there any advice you support me with here please? Thank you.

Best,

Matthew

Dear Matthew,

It looks like your TurbSim wind field extends from 50- to 250-m above MSL. The error is triggered because an aerodynamic analysis node (in AeroDyn) is located at 40.998 m above MSL. Does this location of an aerodynamic analysis node (presumably a blade tip location) make sense to you based on the model you are running (I’m not too familiar with this model)? If so, you’ll need to regenerate your wind data from TurbSim with a different (lower) wind field.

Best regards,

dear Jason,

I’m using FAST.v8.16 and Test24.fst

my turbSim v1.50 input file

31 NumGrid_Z - Vertical grid-point matrix dimension

31 NumGrid_Y - Horizontal grid-point matrix dimension

0.05 TimeStep - Time step [seconds]

630.0 AnalysisTime - Length of analysis time series [seconds]

600.0 UsableTime - Usable length of output time series [seconds] (program will add GridWidth/MeanHHWS seconds) [bjj: was 630]

69.0 HubHt - Hub height [m] (should be > 0.5*GridHeight)

135.0 GridHeight - Grid height [m]

135.0 GridWidth

im getting the following error

Reading a 31x31 grid (135 m wide, 1.5 m to 136.5 m above ground) with a characteristic wind

speed of 15 m/s. This full-field file was generated by TurbSim (v1.50, 25-Sep-2009)

FAST_Solution:CalcOutputs_And_SolveForInputs:SolveOption2:InflowWind_CalcOutput:CalcOutput:IfW_TSF

FWind_CalcOutput [position=(2.5093, 17.863, 138.82) in wind-file coordinates]: FF wind array

boundaries violated. Grid too small in Z direction (Z=138.82 m is above the grid).

i changed GridHeight but i didnt find a solution

i also used the following data in ELASTODYN v1.03. INPUT

66.6 TowerHt

6 TowerBsHt

Thank you in advance

Georgia

Dear Georgia,

A height of Z = 138.82 m seems high for an aerodynamic analysis node if the hub height is in fact 69 m. 138.82 m is higher than double the hub height meaning that the rotor blades would also likely hit the ground! Are you seeing signs of an instability in the model, e.g., unreasonably large tower or blade deflections?

If you’ve changed the hub-height of the NREL 5-MW turbine from 90 to 69 m by decreasing the tower length, did you change the tower mass, stiffness, or mode shapes accordingly? If not, you could have increased the natural frequencies of the tower-bending modes, which would be unrealistic and likely require small time steps to ensure numerical stability of the solution.

Best regards,

dear Jason,

thank you for your reply

i received also that warning

Warning: Turning off Unsteady Aerodynamics due to high angle-of-attack. BladeNode = 5, Blade = 1

So i have to change TMassDen or TwFAStif at elastodyn tower input file??

Than you again

Georgia

Dear Georgia,

If you want a reasonable tower design (e.g., with a first bending natural frequency between 1P and 3P), then yes, you’ll need to change the tower mass, stiffness, and mode shapes.

Best regards,

Dear Jason,

thank you again!!

Is there a method that i should follow in order to change the tower mass, stiffness, and mode shapes?

Best regards,

Georgia

Dear Georgia,

You could start by applying scaling laws, e.g., as discuss on our forum here: http://forums.nrel.gov/t/2-5-mw-wt/1275/7. However, you are not scaling the full wind turbine uniformly; instead, you are just shortening the tower, so, the scaling laws will only get you so far. You’ll likely need to redesign the tower. Again, aiming for a soft-stiff tower design with a first bending natural frequency between 1P and 3P would be a good design constraint.

Best regards,