Hello everyone.
To verify the wake steering effect caused by the yaw control of a wind turbine nacelle, I performed simulations using FAST.Farm under the following conditions.
Target System : IEA-15-240-RWT-UMaineSemi×2
Upstream turbine nacelle yaw angle: 20 deg
Downstream turbine nacelle yaw angle: 0 deg
Wind conditions: Average wind speed of 9 m/s, turbulence intensity of 6.1%
FAST.Farm version : from openfast v3.5.3
When we visualized the wind speed using Paraview on the VTK files generated by running FAST.Farm, we observed clearly discontinuous, abrupt, and unnatural changes in wind speed.
The following two images are snapshots of two consecutive frames.
The links below contain videos created from vtk files of the wind speed fields for three scenarios—using two turbines, using only the upstream turbine, and using only the downstream turbine—all based on the same wind conditions.
We can see that a similar discontinuous flow occurs in all cases.
The fstf files used in the simulation are shown below.
------- FAST.Farm for OpenFAST INPUT FILE -------------------------------------------------
FAST.Farm input file, using two turbines separated by 3D downstream and an offset of 30m, with a turbulent inflow given by one turbsim box
--- SIMULATION CONTROL ---
False Echo - Echo input data to <RootName>.ech? (flag)
FATAL AbortLevel - Error level when simulation should abort (string) {"WARNING", "SEVERE", "FATAL"}
4500 TMax - Total run time (s) [>=0.0]
False UseSC - Use a super controller? (flag)
3 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}}
--- SUPER CONTROLLER --- [used only for UseSC=True]
"unused" SC_FileName - Name/location of the dynamic library {.dll [Windows] or .so [Linux]} containing the Super Controller algorithms (quoated string)
--- 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]
0.25 DT_Mooring - Time step for farm-level mooring coupling with each turbine (s) [used only when Mod_SharedMooring > 0]
--- AMBIENT WIND: PRECURSOR IN VTK FORMAT --- [used only for Mod_AmbWind=1]
30.0 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]
1.0 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]
4.00 DT_Low - Time step for low -resolution wind data interpolation; will be used as the global FAST.Farm time step (s) [>0.0]
0.25 DT_High - Time step for high-resolution wind data interpolation (s) [>0.0]
69 NX_Low - Number of low -resolution spatial nodes in X direction for wind data interpolation (-) [>=2]
61 NY_Low - Number of low -resolution spatial nodes in Y direction for wind data interpolation (-) [>=2]
25 NZ_Low - Number of low -resolution spatial nodes in Z direction for wind data interpolation (-) [>=2]
-240.0 X0_Low - Origin of low -resolution spatial nodes in X direction for wind data interpolation (m)
-720.0 Y0_Low - Origin of low -resolution spatial nodes in Y direction for wind data interpolation (m)
3.0 Z0_Low - Origin of low -resolution spatial nodes in Z direction for wind data interpolation (m)
36.0 dX_Low - Spacing of low -resolution spatial nodes in X direction for wind data interpolation (m) [>0.0]
24.0 dY_Low - Spacing of low -resolution spatial nodes in Y direction for wind data interpolation (m) [>0.0]
24.0 dZ_Low - Spacing of low -resolution spatial nodes in Z direction for wind data interpolation (m) [>0.0]
101 NX_High - Number of high-resolution spatial nodes in X direction for wind data interpolation (-) [>=2]
49 NY_High - Number of high-resolution spatial nodes in Y direction for wind data interpolation (-) [>=2]
51 NZ_High - Number of high-resolution spatial nodes in Z direction for wind data interpolation (-) [>=2]
"InflowWind_01.dat" InflowFile - Name of file containing InflowWind module input parameters (quoted string)
--- WIND TURBINES ---
2 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)
0.0 0.0 0.0 "FFTest_WT1_01.fst" -240 -144 1.0 6.0 6.0 6.0
1440.0 0.0 0.0 "FFTest_WT2_01.fst" 1200 -144 1.0 6.0 6.0 6.0
--- WAKE DYNAMICS ---
1 Mod_Wake - Switch between wake formulations {1:Polar, 2:Curl, 3:Cartesian} (-) (switch)
6.155 dr - Radial increment of radial finite-difference grid (m) [>0.0]
60 NumRadii - Number of radii in the radial finite-difference grid (-) [>=2]
134 NumPlanes - Number of wake planes (-) [>=2]
0.006 f_c - Cutoff (corner) frequency of the low-pass time-filter for the wake advection, deflection, and meandering model [recommended=1.28*U0/R] (Hz) [>0.0] or DEFAULT [DEFAULT=12.5/R, R estimated from dr and NumRadii, not recommended]
DEFAULT C_HWkDfl_O - Calibrated parameter in the correction for wake deflection defining the horizontal offset at the rotor (m ) or DEFAULT [DEFAULT= 0.0 ]
DEFAULT C_HWkDfl_OY - Calibrated parameter in the correction for wake deflection defining the horizontal offset at the rotor scaled with yaw error (m/deg) or DEFAULT [DEFAULT= 0.0 if Mod_Wake is 2, 0.3 otherwise]
DEFAULT C_HWkDfl_x - Calibrated parameter in the correction for wake deflection defining the horizontal offset scaled with downstream distance (- ) or DEFAULT [DEFAULT= 0.0 ]
-0.004 C_HWkDfl_xY - Calibrated parameter for the wake deflection (-) defining the horizontal offset scaled with downstream distance and yaw error (1/deg) or DEFAULT [DEFAULT= 0.0 if Mod_Wake is 2, -0.004 otherwise]
DEFAULT C_NearWake - Calibrated parameter for the near-wake correction (-) [>1.0 and <2.5] or DEFAULT [DEFAULT=1.8]
DEFAULT k_vAmb - Calibrated parameter for the influence of ambient turbulence in the eddy viscosity (-) [>=0.0] or DEFAULT [DEFAULT=0.05 ]
DEFAULT k_vShr - Calibrated parameter for the influence of the shear layer in the eddy viscosity (-) [>=0.0] or DEFAULT [DEFAULT=0.016]
DEFAULT C_vAmb_DMin - Calibrated parameter in the eddy viscosity filter function for ambient turbulence defining the transitional diameter fraction between the minimum and exponential regions (-) [>=0.0 ] or DEFAULT [DEFAULT= 0.0 ]
DEFAULT C_vAmb_DMax - Calibrated parameter in the eddy viscosity filter function for ambient turbulence defining the transitional diameter fraction between the exponential and maximum regions (-) [> C_vAmb_DMin ] or DEFAULT [DEFAULT= 1.0 ]
DEFAULT C_vAmb_FMin - Calibrated parameter in the eddy viscosity filter function for ambient turbulence defining the value in the minimum region (-) [>=0.0 and <=1.0] or DEFAULT [DEFAULT= 1.0 ]
DEFAULT C_vAmb_Exp - Calibrated parameter in the eddy viscosity filter function for ambient turbulence defining the exponent in the exponential region (-) [> 0.0 ] or DEFAULT [DEFAULT= 0.01]
DEFAULT C_vShr_DMin - Calibrated parameter in the eddy viscosity filter function for the shear layer defining the transitional diameter fraction between the minimum and exponential regions (-) [>=0.0 ] or DEFAULT [DEFAULT= 3.0 ]
DEFAULT C_vShr_DMax - Calibrated parameter in the eddy viscosity filter function for the shear layer defining the transitional diameter fraction between the exponential and maximum regions (-) [> C_vShr_DMin ] or DEFAULT [DEFAULT=25.0 ]
DEFAULT C_vShr_FMin - Calibrated parameter in the eddy viscosity filter function for the shear layer defining the value in the minimum region (-) [>=0.0 and <=1.0] or DEFAULT [DEFAULT= 0.2 ]
DEFAULT C_vShr_Exp - Calibrated parameter in the eddy viscosity filter function for the shear layer defining the exponent in the exponential region (-) [> 0.0 ] or DEFAULT [DEFAULT= 0.1 ]
DEFAULT Mod_WakeDiam - Wake diameter calculation model (-) (switch) {1: rotor diameter, 2: velocity based, 3: mass-flux based, 4: momentum-flux based} or DEFAULT [DEFAULT=1]
DEFAULT C_WakeDiam - Calibrated parameter for wake diameter calculation (-) [>0.0 and <0.99] or DEFAULT [DEFAULT=0.95] [unused for Mod_WakeDiam=1]
DEFAULT Mod_Meander - Spatial filter model for wake meandering (-) (switch) {1: uniform, 2: truncated jinc, 3: windowed jinc} or DEFAULT [DEFAULT=3]
DEFAULT C_Meander - Calibrated parameter for wake meandering (-) [>=1.0] or DEFAULT [DEFAULT=1.9]
Please tell me how to address this issue, where such discontinuities and unnatural flow occur.
Best regards,