Dear Bonnie,

With the imposition of an initial x value, the differences between the two graphs have decreased, but they are still present.

So to evaluate if, as you suggested, there is some error in evaluating the position of the nodes, I used ‘Wind1VelX’ as the output of FAST, so that it was a fixed point and that it was therefore comparable with what I get from Turbsim. To make the comparison, therefore, I set the coordinates of a node of the wind grid in the Inflowind input file. In this way I bypassed the node coordinates problem and therefore I expected an equal trend with only a time offset, due to the initial x value imposed in the Inflowind routine.

However, as you can see from figures 1 and 2, the analogous trend that I expected is obtained only for the hub coordinates (fig1), while if I move to the coordinates of another point of the grid (fig2), the differences do not they only limit more to the time offset.

Here is the Turbsim input file that I am using for the test:

```
TurbSim Input File. Valid for TurbSim v1.06.00, 21-Sep-2012
---------Runtime Options-----------------------------------
1393911158 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)
True WrADFF - Output full-field time-series data in TurbSim/AeroDyn form? (Generates Rootname.bts)
False WrBLFF - Output full-field time-series data in BLADED/AeroDyn form? (Generates RootName.wnd)
False WrADTWR - Output tower time-series data? (Generates RootName.twr)
True 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-----------------------
13 NumGrid_Z - Vertical grid-point matrix dimension
13 NumGrid_Y - Horizontal grid-point matrix dimension
0.05 TimeStep - Time step [seconds]
1200 AnalysisTime - Length of analysis time series [seconds] (program will add time if necessary: AnalysisTime = MAX(AnalysisTime, UsableTime+GridWidth/MeanHHWS) )
1200 UsableTime - Usable length of output time series [seconds] (program will add GridWidth/MeanHHWS seconds)
90 HubHt - Hub height [m] (should be > 0.5*GridHeight)
145.00 GridHeight - Grid height [m]
145.00 GridWidth - Grid width [m] (should be >= 2*(RotorRadius+ShaftLength))
0 VFlowAng - Vertical mean flow (uptilt) angle [degrees]
0 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", "TIDAL", or "NONE")
"3" 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 model, 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";"LOG"=logarithmic;"PL"=power law;"H2L"=Log law for TIDAL spectral model;"IEC"=PL on rotor disk, LOG elsewhere; or "default")
90 RefHt - Height of the reference wind speed [m]
8.5 URef - Mean (total) wind speed at the reference height [m/s] (or "default" for JET wind profile)
default ZJetMax - Jet height [m] (used only for JET wind profile, valid 70-490 m)
0.14 PLExp - Power law exponent [-] (or "default")
0.03 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 (or "default")
default PC_UV - Hub mean u'v' Reynolds stress (or "default")
default PC_VW - Hub mean v'w' Reynolds stress (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-------------------
"C:\Users\Luigi\Dropbox\Tesi\NREL\Turbsim\coh_events\EventData\" CTEventPath - Name of the path where event data files are located
"Random" CTEventFile - Type of event files ("LES", "DNS", or "RANDOM")
true Randomize - Randomize the disturbance scale and locations? (true/false)
1.0 DistScl - Disturbance scale (ratio of wave height to rotor disk). (Ignored when Randomize = true.)
0.5 CTLy - Fractional location of tower centerline from right (looking downwind) to left side of the dataset. (Ignored when Randomize = true.)
0.5 CTLz - Fractional location of hub height from the bottom of the dataset. (Ignored when Randomize = true.)
30.0 CTStartTime - Minimum start time for coherent structures in RootName.cts [seconds]
==================================================
NOTE: Do not add or remove any lines in this file!
==================================================
```