Variable inflow issue using Mod_AmbWind =2

[fbelli997]

Dear Community,

I'm trying to run some simulations using Mod_AmbWind = 2 to time-varying wind direction in the inflow.

Unfortunatelly when i check the VTKs on paraview, I notice some unexpected artifacts in the inflow/frames.
I attach here below a short video showing the behaviour of the VTKs.

inflow_variability.mp4

I'm currently running FASTfarm using the curl model with IEA15MW wind turbine model coupled with Volturn US platform.
In the .dat file, the Windtype is set on 2, and parameters for Uniform wind file are set as:

"variable_inflow_rated.wnd"                 Filename_Uni - Filename of time series data for uniform wind field.      (-)
150.0                  RefHt_Uni   - Reference height for horizontal wind speed                (m)
240.0                  RefLength   - Reference length for linear horizontal and vertical sheer (-)

regarding the grid of FASTfarm, I set it as:

------- FAST.Farm for OpenFAST INPUT FILE -------------------------------------------------
Two turbines with shared moorings
--- SIMULATION CONTROL ---
False             Echo               - Echo input data to <RootName>.ech? (flag)
FATAL             AbortLevel         - Error level when simulation should abort (string) {"WARNING", "SEVERE", "FATAL"}
4600               TMax               - Total run time (s) [>=0.0]
2                 Mod_AmbWind        - Ambient wind model (-) (switch) {1: high-fidelity precursor in VTK format, 2: one InflowWind module, 3: multiple instances of InflowWind module}
2                 Mod_WaveField      - Wave field handling (-) (switch) {1: use individual HydroDyn inputs without adjustment, 2: adjust wave phases based on turbine offsets from farm origin}
0                 Mod_SharedMooring  - Shared mooring system model (switch) {0: None, 3=MoorDyn}}
--- SHARED MOORING SYSTEM --- [used only for Mod_SharedMoor>0]
"" SharedMoorFile  - Name of file containing shared mooring system input parameters (quoted string) [used only when Mod_SharedMooring > 0]
0.05              DT_Mooring         - Time step for farm-level mooring coupling with each turbine (s) [used only when Mod_SharedMooring > 0]
false              WrMooringVis       - Write shared mooring visualization, at the global FAST.Farm time step (-) [only used for Mod_SharedMooring=3]
--- AMBIENT WIND: PRECURSOR IN VTK FORMAT --- [used only for Mod_AmbWind=1]
2.0               DT_Low-VTK         - Time step for low -resolution wind data input files; will be used as the global FAST.Farm time step (s) [>0.0]
0.200000          DT_High-VTK        - Time step for high-resolution wind data input files (s) [>0.0]
"unused"          WindFilePath       - Path name to VTK wind data files from precursor (string)
False             ChkWndFiles        - Check all the ambient wind files for data consistency? (flag)
--- AMBIENT WIND: INFLOWWIND MODULE --- [used only for Mod_AmbWind=2 or 3]
1                DT_Low             - Time step for low -resolution wind data interpolation; will be used as the global FAST.Farm time step (s) [>0.0]
0.5                DT_High            - Time step for high-resolution wind data interpolation (s) [>0.0]
261                NX_Low             - Number  of low -resolution spatial nodes in X direction for wind data interpolation (-) [>=2]
261                NY_Low             - Number  of low -resolution spatial nodes in Y direction for wind data interpolation (-) [>=2]
31                NZ_Low             - Number  of low -resolution spatial nodes in Z direction for wind data interpolation (-) [>=2]
0              	  X0_Low             - Origin  of low -resolution spatial nodes in X direction for wind data interpolation (m)
-1957.5            Y0_Low             - Origin  of low -resolution spatial nodes in Y direction for wind data interpolation (m)
3                 Z0_Low             - Origin  of low -resolution spatial nodes in Z direction for wind data interpolation (m)
15                dX_Low             - Spacing of low -resolution spatial nodes in X direction for wind data interpolation (m) [>0.0]
15                dY_Low             - Spacing of low -resolution spatial nodes in Y direction for wind data interpolation (m) [>0.0]
15                dZ_Low             - Spacing of low -resolution spatial nodes in Z direction for wind data interpolation (m) [>0.0]
63                NX_High            - Number  of high-resolution spatial nodes in X direction for wind data interpolation (-) [>=2]
61                NY_High            - Number  of high-resolution spatial nodes in Y direction for wind data interpolation (-) [>=2]
61                NZ_High            - Number  of high-resolution spatial nodes in Z direction for wind data interpolation (-) [>=2]
"inflow/6_turbines/variable_inflow.dat"  InflowFile         - Name of file containing InflowWind module input parameters (quoted string)
--- WIND TURBINES ---
6                 NumTurbines        - Number of wind turbines (-) [>=1]                         [last 6 columns below used only for Mod_AmbWind=2 or 3] 
WT_X     WT_Y  WT_Z     WT_FASTInFile                     X0_High  Y0_High  Z0_High  dX_High  dY_High  dZ_High
(m)      (m)   (m)      (string)                           (m)      (m)      (m)      (m)      (m)      (m)
300      480     0.000     "wind_turbines/T1/wind_var.fst"     150    330     3       4.5       5       5
1500     480      0.000    "wind_turbines/T2/wind_var.fst"    1350    330     3       4.5       5       5
2700     480      0.000    "wind_turbines/T3/wind_var.fst"    2550    330     3       4.5       5       5
300      -480     0.000    "wind_turbines/T4/wind_var.fst"     150    -630     3       4.5       5       5
1500     -480      0.000   "wind_turbines/T5/wind_var.fst"    1350    -630     3       4.5       5       5
2700     -480     0.000    "wind_turbines/T6/wind_var.fst"    2550    -630     3       4.5       5       5

Regarding the wnd file, i set a time step of 0.05.

# Wind file with changing direction (smoothed ramp)
# Time[s]	Vh_ref[m/s]	Delta[deg]	Vz[m/s]	HLinShr	VShr	VLinShr	VGust[m/s]
0.00	10.59	0.00	0.00	0.00	0.00	0.00	0.00
0.05	10.59	0.00	0.00	0.00	0.00	0.00	0.00
0.10	10.59	0.00	0.00	0.00	0.00	0.00	0.00
0.15	10.59	0.00	0.00	0.00	0.00	0.00	0.00

Am I setting something wrong in the .wnd, .dat or inside the fstf files?

Thank you in advance for your help.

Federico

[jjonkman]

Dear @fbelli997,

It appears that wakes are bouncing back into the domain instead of leaving the domain when there is sizeable skew of the wake planes relative to the boundary. We recently submitted a fix to a similar issue in the following PR: #3025. I'm hoping the changes in this PR solve your issue as well; can you check?

The changes in this FAST.Farm PR are planned to be released soon in OpenFAST v5.0.0, but perhaps you could recompile FAST.Farm with the changes before that and see if they resolve your issue.

Best regards,

[fbelli997]

Hi Jason,
thanks for the hint and PR #3025. I managed to build FAST.Farm from the dev branch on Windows, but the executable won’t run because it requires the Intel MKL runtime (when I launch it, I get a missing mkl_intel_thread.2.dll error).

Would you be able to share a precompiled Windows FAST.Farm.exe that already includes the required runtime dependencies for the dev branch including PR #3025? That would let me quickly test whether the fix resolves the wake “bounce back” issue in my case.

Best regards,
Federico