Facing error- using without turbulence in Wind file

Dear sir,

My junior Ms.Silpa facing following issue, she asked me to put this in the forum, i request please help her

I am running FAST to analyze the NREL 5MW wind turbine in various wind speed conditions. In this model I am using 16m/s stochastic wind speed which is generated from TurbSim without including turbulence. Its shows error which is attached here.Though i have changed gridwidth also.
If I am running with turbulence,its running normally without error. Here with I attached the turbsim input file. I request you to kindly do the needful.

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

---------Runtime Options-----------------------------------
512117 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-----------------------
31 NumGrid_Z - Vertical grid-point matrix dimension
31 NumGrid_Y - Horizontal grid-point matrix dimension
0.05 TimeStep - Time step [seconds]
1100.0 AnalysisTime - Length of analysis time series [seconds]
1030.0 UsableTime - Usable length of output time series [seconds] (program will add GridWidth/MeanHHWS seconds)
90.0 HubHt - Hub height [m] (should be > 0.5GridHeight)
170.0 GridHeight - Grid height [m]
220.0 GridWidth - Grid width [m] (should be >= 2
0 VFlowAng - Vertical mean flow (uptilt) angle [degrees]
0 HFlowAng - Horizontal mean flow (skew) angle [degrees]

--------Meteorological Boundary Conditions-------------------
NONE TurbModel - Turbulence model (“IECKAI”=Kaimal, “IECVKM”=von Karman, “GP_LLJ”, “NWTCUP”, “SMOOTH”, “WF_UPW”, “WF_07D”, “WF_14D”, or “NONE”)
“1” 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 RefHt - Height of the reference wind speed [m]
16 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 Mani (for Ms. Silpa),

My guess is that your model is going numerically unstable for some reason. Warnings regarding a “small angle approximation violation,” warnings regarding “supersonic blades,” a simulation crash, or very large deflections that occur in the time series are good signs of a numerical instability. Without knowing more about your simulation settings, it’s hard to know that what the problem is. Please use “Search…” in the upper right of the forum to search for “small angle assumption” to see how we’ve solved similar problems in the past.

I’m not sure what you are trying to do, but the TurbSim input file you’ve pasted in doesn’t seem to match the message written by the FAST simulation. For example, FAST is reporting that it is reading a 41x41 grid, but your TurbSim input file shows a 31x31 grid. Also, I recommend using an AeroDyn’s so-called “hub-height” wind file format for modeling wind conditions that are not turbulent instead of TurbSim-generated wind with TurbModel set to “NONE”.

Best regards,