FAST V8.016 Problem Occured

Hi, I am new on the FAST, and met a problem about the simulation of FAST V8.016, attatched please find the screen. Thanks in advance.

Dear @Deyi.Fu,

I answered a similar question asked in Feb '17 in the following forum topic: Dynamic Analysis of offshore wind turbine on triceratop floating platform - #11 by Jason.Jonkman.

Best regards,

Dear Jason,
Many thanks! I will try to modify the related settings.
best regards.

Dear Jason,
I tried a lot to modify the .inp file for the Turbsim, but still there is a same error. Would you please do me a favor to have a look at it?
.inp detailed information as following:
TurbSim Input File. Valid for TurbSim v1.50; 17-May-2010; Example file that can be used with simulations for the NREL 5MW Baseline Turbine; note that UsableTime has been decreased in this file so that the file distributed with the FAST CertTest isn’t as large

---------Runtime Options-----------------------------------
13428 RandSeed1 - First random seed (-2147483648 to 2147483647)
RanLux RandSeed2 - Second random seed (-2147483648 to 2147483647) for intrinsic pRNG, or an alternative pRNG: “RanLux” or “RNSNLW”
False WrBHHTP - Output hub-height turbulence parameters in binary form? (Generates RootName.bin)
False WrFHHTP - Output hub-height turbulence parameters in formatted form? (Generates RootName.dat)
False WrADHH - Output hub-height time-series data in AeroDyn form? (Generates RootName.hh)
False WrADFF - Output full-field time-series data in TurbSim/AeroDyn form? (Generates RootName.bts)
True WrBLFF - Output full-field time-series data in BLADED/AeroDyn form? (Generates RootName.wnd)
False WrADTWR - Output tower time-series data? (Generates RootName.twr)
False WrFMTFF - Output full-field time-series data in formatted (readable) form? (Generates RootName.u, RootName.v, RootName.w)
False WrACT - Output coherent turbulence time steps in AeroDyn form? (Generates RootName.cts)
True Clockwise - Clockwise rotation looking downwind? (used only for full-field binary files - not necessary for AeroDyn)
0 ScaleIEC - Scale IEC turbulence models to exact target standard deviation? [0=no additional scaling; 1=use hub scale uniformly; 2=use individual scales]

--------Turbine/Model Specifications-----------------------
29 NumGrid_Z - Vertical grid-point matrix dimension
29 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]
90.0 HubHt - Hub height [m] (should be > 0.5GridHeight)
140.0 GridHeight - Grid height [m]
140.0 GridWidth - Grid width [m] (should be >= 2
0 VFlowAng - Vertical mean flow (uptilt) angle [degrees]
-8 HFlowAng - Horizontal mean flow (skew) angle [degrees]

--------Meteorological Boundary Conditions-------------------
IECKAI TurbModel - Turbulence model (“IECKAI”=Kaimal, “IECVKM”=von Karman, “GP_LLJ”, “NWTCUP”, “SMOOTH”, “WF_UPW”, “WF_07D”, “WF_14D”, or “NONE”)
“1-ed2” IECstandard - Number of IEC 61400-x standard (x=1,2, or 3 with optional 61400-1 edition number (i.e. “1-Ed2”) )
“B” IECturbc - IEC turbulence characteristic (“A”, “B”, “C” or the turbulence intensity in percent) (“KHTEST” option with NWTCUP, not used for other models)
NTM IEC_WindType - IEC turbulence type (“NTM”=normal, “xETM”=extreme turbulence, “xEWM1”=extreme 1-year wind, “xEWM50”=extreme 50-year wind, where x=wind turbine class 1, 2, or 3)
default ETMc - IEC Extreme turbulence model “c” parameter [m/s]
PL WindProfileType - Wind profile type (“JET”=Low-level jet,“LOG”=Logarithmic,“PL”=Power law, or “default”, or “USR”=User-defined)
90.0 RefHt - Height of the reference wind speed [m]
3.0 URef - Mean (total) wind speed at the reference height [m/s]
default ZJetMax - Jet height [m] (used only for JET wind profile, valid 70-490 m)
default PLExp - Power law exponent [-] (or “default”)
default Z0 - Surface roughness length [m] (or “default”)

--------Non-IEC Meteorological Boundary Conditions------------
default Latitude - Site latitude [degrees] (or “default”)
0.05 RICH_NO - Gradient Richardson number
default UStar - Friction or shear velocity [m/s] (or “default”)
default ZI - Mixing layer depth [m] (or “default”)
default PC_UW - Hub mean u’w’ Reynolds stress [(m/s)^2] (or “default”)
default PC_UV - Hub mean u’v’ Reynolds stress [(m/s)^2] (or “default”)
default PC_VW - Hub mean v’w’ Reynolds stress [(m/s)^2] (or “default”)
default IncDec1 - u-component coherence parameters (e.g. “10.0 0.3e-3” in quotes) (or “default”)
default IncDec2 - v-component coherence parameters (e.g. “10.0 0.3e-3” in quotes) (or “default”)
default IncDec3 - w-component coherence parameters (e.g. “10.0 0.3e-3” in quotes) (or “default”)
default CohExp - Coherence exponent (or “default”)

--------Coherent Turbulence Scaling Parameters-------------------
“M:\coh_events\eventdata” CTEventPath - Name of the path where event data files are located
“Random” CTEventFile - Type of event files (“random”, “les” or “dns”)
true Randomize - Randomize disturbance scale and location? (true/false)
1.0 DistScl - Disturbance scale (ratio of dataset height to rotor disk).
0.5 CTLy - Fractional location of tower centerline from right (looking downwind) to left side of the dataset.
0.5 CTLz - Fractional location of hub height from the bottom of the dataset.
10.0 CTStartTime - Minimum start time for coherent structures in RootName.cts [seconds]

NOTE: Do not add or remove any lines in this file!

Dear Jason,
I have tried the following cases:
GridHeight=140;GridWidth=140; then Failed;
GridHeight=145;GridWidth=145; then Failed;
GridHeight=175;GridWidth=175; then Failed;
GridHeight=180;GridWidth=180; then Failed;
GridHeight=130;GridWidth=130; then Failed;
Finally, I try to change the “NRELOffshrBsline5MW_Onshore_AeroDyn15.dat”,
TwrElev TwrDiam TwrCd
(m) (m) (-)
0.0000000E+00 6.0000000E+00 1.0000000E+00
8.5261000E+00 5.7870000E+00 1.0000000E+00
To be:
TwrElev TwrDiam TwrCd
(m) (m) (-)
3.5000000E+00 6.0000000E+00 1.0000000E+00
8.5261000E+00 5.7870000E+00 1.0000000E+00
then there is an another error:

Dear @Deyi.Fu,

So, did you finally settle on a GridHeight/GridWidth in TurbSim that works for you in combination with the lowest value of TwrElev in AeroDyn? Which values did you settle on?

The error regarding “no valid value of phi” has been discussed many times on this forum, e.g.: Process stopped - #3 by Leire.Gandiaga.

However, the error in your case is proceeded by warning about “large blade deflection”, which suggests something else is wrong with your simulation set up. This warning has also been discussed many times in this forum.

Best regards,

Dear Jason,
Finally I set GridHeight=GridWidth=140m, but there is still the same error. To solve this problem I changed the NumTwrNds from 12 to 9 of the ''NRELOffshrBsline5MW_Onshore_AeroDyn15.dat", and delete the first three lines, and then there is another error.

I guess maybe the problem is caused due to the windspeed, I adjust the windspeed value to 10m/s, but the same problem~It is a pity.

Dear @Deyi.Fu,

Finally I set GridHeight=GridWidth=140m, but there is still the same error. To solve this problem I changed the NumTwrNds from 12 to 9 of the ''NRELOffshrBsline5MW_Onshore_AeroDyn15.dat", and delete the first three lines

OK, to solve the original issue you now generate a turbulent wind field that extends from 20 to 160 m above the ground and set your first tower aerodynamics node to be 25.579 m above the ground, which is well within the wind domain. That makes sense.

Regarding your new error, have you initialized the rotor speed (RotSpeed in ElastoDyn) and blade pitch angle (BlPitch(1-3) in ElastoDyn) to their expected (mean) values for the mean wind speed you are simulating following our general guidance? If not, the controller may not respond properly and the FAST/OpenFAST can produce unphyiscal results. Appropriate initiation conditions for the NREL 5-MW wind turbine are documented in Figure 9-1 of its specifications report: At 10 m/s, these should be RotSpeed = 11.43 rpm and BlPitch = 0deg. At 18 m/s, these should be RotSpeed = 12.10 rpm and BlPitch = 14.92 rpm. Do the simulations run as expected with this proper initial conditions?

Best regards,

Thanks Mr Jason
According to your suggestion, I modified the NRELOffshrBsline5MW_Onshore_ElastoDyn.dat, to set the B1Pitch =14.92 ;B2Pitch =14.92;B3Pitch =14.92 and RotSpeed= 12.10 rpm, still there is an error.

Hi, Jason, there is another question, as you mentioned, the rotor speed ( RotSpeed in ElastoDyn) and blade pitch angle ( BlPitch(1-3) in ElastoDyn) need to be modified according to the wind speed , and it is documented in Figure 9-1 of its specifications report, However, do we have a table of the data showed on Figure 9-1, it maybe plus for us to set the initiation conditions.
best regards.

Dear @Deyi.Fu,

I shared a tabular listing of the values contained in Figure 9-1 of the NREL 5-MW specifications report in my post dated Mar 26, 2014 in the following forum topic: NREL5MW Rotor Speed Data.

Changing the initial conditions eliminated the “large blade deflection” warning, but you are still receiving the “no valid value of phi” error. Please refer to the forum topic I linked above for the solution. Upgrading from FAST v8.16 to OpenFAST is likely the easiest solution.

Best regards,

Dear Jason,
Many thanks! I get the simulation results with OpenFAST, thank you!

Dear Jason, Sorry for the disturblence.
I test a selfdefined .fst, and there is an error:

**OpenFAST input file heading: **
** FAST Certification Test #18: NREL 5.0 MW Baseline Wind Turbine (Onshore) **

**Running ElastoDyn. **
**Nodal outputs section of ElastoDyn input file not found or improperly formatted. **
**Running AeroDyn. **
**AD15 Nodal Outputs: Nodal output section of AeroDyn input file not found or improperly formatted. **
Skipping nodal outputs.
**Running InflowWind. **

** Reading a 29x29 grid (140 m wide, 20 m to 160 m above ground) with a characteristic wind speed **
** of 19 m/s.**

** Processed 12148 time steps of 20-Hz full-field data (607.35 seconds). **
** Time: 0 of 600 seconds. **
**The BEM solution is being turned off due to low TSR. (TSR = 1.2268). This warning will not be **
**repeated though the condition may persist. (See GeomPhi output channel.) **

**FAST_Solution:FAST_AdvanceStates:ED_ABM4:ED_CalcContStateDeriv:SetCoordSy:Small angle assumption **
**violated in SUBROUTINE SmllRotTrans() due to a large blade deflection (ElastoDyn SetCoordSy). The **
**solution may be inaccurate. Simulation continuing, but future warnings from SmllRotTrans() will **
**be suppressed. **
** Additional debugging message from SUBROUTINE SmllRotTrans(): 1 s **

**Warning: SkewedWakeCorrection encountered a large value of chi (170.01 deg), so the yaw **
**correction will be limited. This warning will not be repeated though the condition may persist. **
**See the AD15 chi output channels, and consider turning off the Pitt/Peters skew model (set **
**SkewMod=1) if this condition persists. **

**FAST_Solution:FAST_AdvanceStates:SolveOption2c_Inp2AD_SrvD:InflowWind_CalcOutput:CalcOutput:IfW_FF **
**Wind_CalcOutput [position=(-173.19, -925.31, 188.76) in wind-file coordinates]: FF wind array **
**boundaries violated. Grid too small in Z direction (Z=188.76 m is above the grid). **
**FAST_AdvanceStates:AD_UpdateStates:BEMT_UpdateStates:UpdatePhi(node 5, blade **
**2):BEMT_UnCoupledSolve:There is no valid value of phi for these operating conditions: Vx = **
**419.54, Vy = -2609.9, rlocal = 11.289, theta = 0.55504, geometric phi = 2.9822. This warning will **
**not be repeated though the condition may persist. (See GeomPhi output channel.) **

a OpenFAST encountered an error at simulation time 1.3 of 600 seconds. **
** Simulation error level: FATAL ERROR

do you have any suggestion about this kind of error?

Dear @Deyi.Fu,

It is the “FF wind array boundaries violated” error that is causing OpenFAST to abort. Given the “large blade deflection” warning and odd position of an analysis node (-173.19, -925.31, 188.76), I’m guessing your model is numerically unstable. I assume that are you now using proper initial conditions? Perhaps the time step (DT) is set too large?

You mention that your input file is “self defined”, but it also looks like you are running the land-based NREL 5-MW baseline model. I’m not sure what you’ve changed in this model, but I would first start with the following model available in the OpenFAST r-test: r-test/glue-codes/openfast/5MW_Land_DLL_WTurb at main · OpenFAST/r-test · GitHub.

Best regards,

Dear Jason,
yes, what I used is the NREL 5MW model, only with some little modifications about the wind type, etc. The DT is set to be 0.05, is it too large? and about the initial conditions, I used the values according to your suggestion.

Dear @Deyi.Fu.,

The large time step is likely the problem. The time step used by this r-test case is DT = 0.00625 s. Lowering DT should solve the problem.

Best regards,

Dear Jason,
OK, got it, many thanks!
best regards.