Need to prescribe nacelle/platform motion in FAST.Farm using external 6-DOF motion from OrcaFlex

[cjking1226]

Hello,
I would like to use FAST.Farm to study wake behavior of a floating wind turbine, but the platform/nacelle motion comes from OrcaFlex (or tank tests), not OpenFAST.

I found that AeroDyn Driver supports prescribed 6-DOF motion via BaseMotionType, but AeroDyn Driver cannot be used inside FAST.Farm.

So my question is:

Is there any way to run FAST.Farm while prescribing an external nacelle/platform motion time series to the turbine?
If not, is this feature planned or is there a recommended workaround?

This capability is important for cases where the aerodynamic wake must be simulated using measured or externally-computed platform motions rather than OpenFAST-predicted motions.

Thank you!

[jjonkman]

Dear @cjking1226,

Regarding prescribing the 6-DOF rigid-body motion of an OpenFAST model, see a similar question discussed here: #617. However, this discussion assumes you know the motion a head of time (before running the simulation).

I suspect what you really want is two-way coupling between OrcaFlex (or tank test) and FAST.Farm, but this would require code development. I've suggested the development of an OrcaFlex interface to FAST.Farm with Orcina, but I'm not aware of active development in that direction yet.

Best regards,

[cjking1226]

Dear @cjking1226,

Regarding prescribing the 6-DOF rigid-body motion of an OpenFAST model, see a similar question discussed here: #617. However, this discussion assumes you know the motion a head of time (before running the simulation).

I suspect what you really want is two-way coupling between OrcaFlex (or tank test) and FAST.Farm, but this would require code development. I've suggested the development of an OrcaFlex interface to FAST.Farm with Orcina, but I'm not aware of active development in that direction yet.

Best regards,

Dear @jjonkman,

Thank you very much for your clarification. I would like to further confirm one point:

Can FAST.Farm be coupled with AeroDyn Driver?
Since AeroDyn Driver allows prescribing the full 6-DOF nacelle/base motion, I was wondering whether FAST.Farm could use AeroDyn Driver as its aerodynamic sub-module while still computing the wake using the DWM model.

If this is not directly supported, could you please advise what the recommended pathway is?
For example:

Is a custom interface required to couple FAST.Farm with AeroDyn Driver?

Can this be achieved via the existing MATLAB/Simulink interface or by modifying/compiling the FAST.Farm source code?

My goal is to compute wake effects under prescribed nacelle motions obtained from OrcaFlex or tank tests, so I am trying to determine the appropriate development direction.

Thank you again for your guidance.

Best regards,
cjking1226

[jjonkman]

Dear @cjking1226,

There is no interface between FAST.Farm and the standalone AeroDyn driver.

If you wish to prescribe the motion of a rigid turbine within FAST.Farm based on precomputed motions (which is what is possible through the AeroDyn driver), I would suggest disabling all DOFs in ElastoDyn except the platform DOFs and follow the approach outlined in issue #617 to prescribe the platform motion. Of course, this would require that your turbine spins at a constant RPM. Additional changes would be required if you wish to prescribe other time-varying motions beyond the 6 platform DOFs.

Best regards,

[cjking1226]

Dear @cjking1226,

There is no interface between FAST.Farm and the standalone AeroDyn driver.

If you wish to prescribe the motion of a rigid turbine within FAST.Farm based on precomputed motions (which is what is possible through the AeroDyn driver), I would suggest disabling all DOFs in ElastoDyn except the platform DOFs and follow the approach outlined in issue #617 to prescribe the platform motion. Of course, this would require that your turbine spins at a constant RPM. Additional changes would be required if you wish to prescribe other time-varying motions beyond the 6 platform DOFs.

Dear @jjonkman 4,

Thank you for your explanation. I understand the approach of prescribing platform motion via ElastoDyn as in issue #617, but in my case I need to prescribe full nacelle/hub 6-DOF motion, similar to what AeroDyn Driver accepts through a Motion.csv file (position, velocity, acceleration). This motion comes from OrcaFlex/tank tests and is required for wake-effect studies in FAST.Farm.

You mentioned “additional changes” would be needed beyond the 6 platform DOFs. Could you please clarify which modules must be modified (ElastoDyn, AeroDyn inputs, or FAST.Farm glue code)? My goal is simply to enable FAST.Farm to read a time-series motion file for the nacelle. A short indication of where such functionality should be added would help me implement it correctly.

Best regards,
CJ

[jjonkman]

Dear @cjking1226,

As has been discussed on our forum, you can always place the platform reference point of ElastoDyn at the tower top. eliminating the tower from the model. And without the YawDOF disabled, the nacelle will follow the platform. So, #617 can be used to prescribe the 6-DOF motion of the nacelle.

I'm not sure if your use case needs other motions prescribed, such as the rotor rotation (if nonconstant) or blade-pitch, but these would have to be done through the controller.

Best regards,

[cjking1226]

Dear @cjking1226,

As has been discussed on our forum, you can always place the platform reference point of ElastoDyn at the tower top. eliminating the tower from the model. And without the YawDOF disabled, the nacelle will follow the platform. So, #617 can be used to prescribe the 6-DOF motion of the nacelle.

I'm not sure if your use case needs other motions prescribed, such as the rotor rotation (if nonconstant) or blade-pitch, but these would have to be done through the controller.

Best regards,

Dear @jjonkman ,

I would like to clarify what you mean by “placing the platform reference point at the tower top” in ElastoDyn. I tried to interpret this literally by setting TowerBsHt = tower-top elevation, TowerHt = 0, and PtfmRefzt = tower-top, but ElastoDyn validation fails (TowerHt > 0, TowerBsHt < TowerHt, PtfmRefzt ≤ TowerBsHt, etc.).

Does your statement mean that the external MCKF loads/motions should be defined with respect to the tower-top reference, while ElastoDyn still keeps a minimal dummy tower and a geometrically consistent PtfmRefzt, rather than physically moving the platform reference point to the tower top in the ElastoDyn geometry?
My current ElastoDyn setup is:

Best regards,------- ELASTODYN v1.03.* INPUT FILE -------------------------------------------
IEA 15 MW offshore reference model on UMaine VolturnUS-S semi-submersible floating platform
---------------------- SIMULATION CONTROL --------------------------------------
False Echo - Echo input data to ".ech" (flag)
3 Method - Integration method: {1: RK4, 2: AB4, or 3: ABM4} (-)
"default" DT Integration time step (s)
---------------------- DEGREES OF FREEDOM --------------------------------------
True FlapDOF1 - First flapwise blade mode DOF (flag)
True FlapDOF2 - Second flapwise blade mode DOF (flag)
True EdgeDOF - First edgewise blade mode DOF (flag)
False TeetDOF - Rotor-teeter DOF (flag) [unused for 3 blades]
False DrTrDOF - Drivetrain rotational-flexibility DOF (flag)
False GenDOF - Generator DOF (flag)
False YawDOF - Yaw DOF (flag)
False TwFADOF1 - First fore-aft tower bending-mode DOF (flag)
False TwFADOF2 - Second fore-aft tower bending-mode DOF (flag)
False TwSSDOF1 - First side-to-side tower bending-mode DOF (flag)
False TwSSDOF2 - Second side-to-side tower bending-mode DOF (flag)
False PtfmSgDOF - Platform horizontal surge translation DOF (flag)
False PtfmSwDOF - Platform horizontal sway translation DOF (flag)
False PtfmHvDOF - Platform vertical heave translation DOF (flag)
False PtfmRDOF - Platform roll tilt rotation DOF (flag)
False PtfmPDOF - Platform pitch tilt rotation DOF (flag)
False PtfmYDOF - Platform yaw rotation DOF (flag)
---------------------- INITIAL CONDITIONS --------------------------------------
0 OoPDefl - Initial out-of-plane blade-tip displacement (meters)
0 IPDefl - Initial in-plane blade-tip deflection (meters)
1. BlPitch(1) - Blade 1 initial pitch (degrees)
1. BlPitch(2) - Blade 2 initial pitch (degrees)
1. BlPitch(3) - Blade 3 initial pitch (degrees) [unused for 2 blades]
0 TeetDefl - Initial or fixed teeter angle (degrees) [unused for 3 blades]
0 Azimuth - Initial azimuth angle for blade 1 (degrees)
6 RotSpeed - Initial or fixed rotor speed (rpm)
0 NacYaw - Initial or fixed nacelle-yaw angle (degrees)
0 TTDspFA - Initial fore-aft tower-top displacement (meters)
0 TTDspSS - Initial side-to-side tower-top displacement (meters)
0 PtfmSurge - Initial or fixed horizontal surge translational displacement of platform (meters)
0 PtfmSway - Initial or fixed horizontal sway translational displacement of platform (meters)
0 PtfmHeave - Initial or fixed vertical heave translational displacement of platform (meters)
0 PtfmRoll - Initial or fixed roll tilt rotational displacement of platform (degrees)
0 PtfmPitch - Initial or fixed pitch tilt rotational displacement of platform (degrees)
0 PtfmYaw - Initial or fixed yaw rotational displacement of platform (degrees)
---------------------- TURBINE CONFIGURATION -----------------------------------
3 NumBl - Number of blades (-)
120.97 TipRad - The distance from the rotor apex to the blade tip (meters)
3.97 HubRad - The distance from the rotor apex to the blade root (meters)
-4 PreCone(1) - Blade 1 cone angle (degrees)
-4 PreCone(2) - Blade 2 cone angle (degrees)
-4 PreCone(3) - Blade 3 cone angle (degrees) [unused for 2 blades]
0 HubCM - Distance from rotor apex to hub mass [positive downwind] (meters)
0 UndSling - Undersling length [distance from teeter pin to the rotor apex] (meters) [unused for 3 blades]
0 Delta3 - Delta-3 angle for teetering rotors (degrees) [unused for 3 blades]
0 AzimB1Up - Azimuth value to use for I/O when blade 1 points up (degrees)
-12.098 OverHang - Distance from yaw axis to rotor apex [3 blades] or teeter pin [2 blades] (meters)
0.0 ShftGagL - Distance from rotor apex [3 blades] or teeter pin [2 blades] to shaft strain gages [positive for upwind rotors] (meters)
-6.0 ShftTilt - Rotor shaft tilt angle (degrees)
-5.125 NacCMxn - Downwind distance from the tower-top to the nacelle CM (meters)
0.0 NacCMyn - Lateral distance from the tower-top to the nacelle CM (meters)
4.315 NacCMzn - Vertical distance from the tower-top to the nacelle CM (meters)
0.0 NcIMUxn - Downwind distance from the tower-top to the nacelle IMU (meters)
0.0 NcIMUyn - Lateral distance from the tower-top to the nacelle IMU (meters)
0.0 NcIMUzn - Vertical distance from the tower-top to the nacelle IMU (meters)
5.6141 Twr2Shft - Vertical distance from the tower-top to the rotor shaft (meters)
147 TowerHt - Height of tower above ground level [onshore] or MSL [offshore] (meters)
146 TowerBsHt - Height of tower base above ground level [onshore] or MSL [offshore] (meters)
0 PtfmCMxt - Downwind distance from the ground level [onshore] or MSL [offshore] to the platform CM (meters)
0 PtfmCMyt - Lateral distance from the ground level [onshore] or MSL [offshore] to the platform CM (meters)
-14.400 PtfmCMzt - Vertical distance from the ground level [onshore] or MSL [offshore] to the platform CM (meters)
146 PtfmRefzt - Vertical distance from the ground level [onshore] or MSL [offshore] to the platform reference point (meters)
---------------------- MASS AND INERTIA ----------------------------------------
0 TipMass(1) - Tip-brake mass, blade 1 (kg)
0 TipMass(2) - Tip-brake mass, blade 2 (kg)
0 TipMass(3) - Tip-brake mass, blade 3 (kg) [unused for 2 blades]
69131 HubMass - Hub mass (kg)
969952 HubIner - Hub inertia about rotor axis [3 blades] or teeter axis [2 blades] (kg m^2)
1836784 GenIner - Generator inertia about HSS (kg m^2)
644857 NacMass - Nacelle mass (kg)
32929058 NacYIner - Nacelle inertia about yaw axis (kg m^2)
28249 YawBrMass - Yaw bearing mass (kg)
1.7838E+07 PtfmMass - Platform mass (kg)
1.2507E+10 PtfmRIner - Platform inertia for roll tilt rotation about the platform CM (kg m^2)
1.2507E+10 PtfmPIner - Platform inertia for pitch tilt rotation about the platform CM (kg m^2)
2.3667E+10 PtfmYIner - Platform inertia for yaw rotation about the platform CM (kg m^2)
---------------------- BLADE ---------------------------------------------------
50 BldNodes - Number of blade nodes (per blade) used for analysis (-)
"../IEA-15-240-RWT/IEA-15-240-RWT_ElastoDyn_blade.dat" BldFile1 - Name of file containing properties for blade 1 (quoted string)
"../IEA-15-240-RWT/IEA-15-240-RWT_ElastoDyn_blade.dat" BldFile2 - Name of file containing properties for blade 2 (quoted string)
"../IEA-15-240-RWT/IEA-15-240-RWT_ElastoDyn_blade.dat" BldFile3 - Name of file containing properties for blade 3 (quoted string) [unused for 2 blades]
---------------------- ROTOR-TEETER --------------------------------------------
0 TeetMod - Rotor-teeter spring/damper model {0: none, 1: standard, 2: user-defined from routine UserTeet} (switch) [unused for 3 blades]
0 TeetDmpP - Rotor-teeter damper position (degrees) [used only for 2 blades and when TeetMod=1]
0 TeetDmp - Rotor-teeter damping constant (N-m/(rad/s)) [used only for 2 blades and when TeetMod=1]
0 TeetCDmp - Rotor-teeter rate-independent Coulomb-damping moment (N-m) [used only for 2 blades and when TeetMod=1]
0 TeetSStP - Rotor-teeter soft-stop position (degrees) [used only for 2 blades and when TeetMod=1]
0 TeetHStP - Rotor-teeter hard-stop position (degrees) [used only for 2 blades and when TeetMod=1]
0 TeetSSSp - Rotor-teeter soft-stop linear-spring constant (N-m/rad) [used only for 2 blades and when TeetMod=1]
0 TeetHSSp - Rotor-teeter hard-stop linear-spring constant (N-m/rad) [used only for 2 blades and when TeetMod=1]
---------------------- DRIVETRAIN ----------------------------------------------
100 GBoxEff - Gearbox efficiency (%)
1 GBRatio - Gearbox ratio (-)
69737644900 DTTorSpr - Drivetrain torsional spring (N-m/rad)
49418406 DTTorDmp - Drivetrain torsional damper (N-m/(rad/s))
---------------------- FURLING -------------------------------------------------
False Furling - Read in additional model properties for furling turbine (flag) [must currently be FALSE)
"unused" FurlFile - Name of file containing furling properties (quoted string) [unused when Furling=False]
---------------------- TOWER ---------------------------------------------------
20 TwrNodes - Number of tower nodes used for analysis (-)
"IEA-15-240-RWT-UMaineSemi_ElastoDyn_tower.dat" TwrFile - Name of file containing tower properties (quoted string)
---------------------- OUTPUT --------------------------------------------------
True SumPrint - Print summary data to ".sum" (flag)
1 OutFile - Switch to determine where output will be placed: {1: in module output file only; 2: in glue code output file only; 3: both} (currently unused)
True TabDelim - Use tab delimiters in text tabular output file? (flag) (currently unused)
"ES10.3E2" OutFmt - Format used for text tabular output (except time). Resulting field should be 10 characters. (quoted string) (currently unused)
0 TStart - Time to begin tabular output (s) (currently unused)
1 DecFact - Decimation factor for tabular output {1: output every time step} (-) (currently unused)
1 NTwGages - Number of tower nodes that have strain gages for output [0 to 9] (-)
20 TwrGagNd - List of tower nodes that have strain gages [1 to TwrNodes] (-) [unused if NTwGages=0] TwrGagNd - List of tower nodes that have strain gages [1 to TwrNodes] (-) [unused if NTwGages=0] TwrGagNd - List of tower nodes that have strain gages [1 to TwrNodes] (-) [unused if NTwGages=0]
3 NBlGages - Number of blade nodes that have strain gages for output [0 to 9] (-)
5, 9, 13 BldGagNd - List of blade nodes that have strain gages [1 to BldNodes] (-) [unused if NBlGages=0] BldGagNd - List of blade nodes that have strain gages [1 to BldNodes] (-) [unused if NBlGages=0] BldGagNd - List of blade nodes that have strain gages [1 to BldNodes] (-) [unused if NBlGages=0]
OutList - The next line(s) contains a list of output parameters. See OutListParameters.xlsx for a listing of available output channels, (-)
"PtfmTDxi" ————平台纵荡（前后）

"PtfmTDyi" ————平台横荡（左右）

"PtfmTDzi" ————平台垂荡（上下）

"PtfmRDxi" ————平台横摇（左右）

"PtfmRDyi" ————平台纵摇（前后）

"PtfmRDzi" ————平台艏摇（偏航摇）
"Azimuth"
"BldPitch1"
"BldPitch2"
"BldPitch3"
"GenSpeed"
"IPDefl1"
"LSSGagMya"
"LSSGagMza"
"LSSTipMys"
"LSSTipMzs"
"LSShftFys"
"LSShftFzs"
"NacYaw"
"NcIMUTAxs"
"NcIMUTAys"
"NcIMUTAzs"
"OoPDefl1"
"PtfmHeave"
"PtfmPitch"
"PtfmRoll"
"PtfmSurge"
"PtfmSway"
"PtfmYaw"
"RootFxb1"
"RootFxb2"
"RootFxb3"
"RootFxc1"
"RootFxc2"
"RootFxc3"
"RootFyb1"
"RootFyb2"
"RootFyb3"
"RootFyc1"
"RootFyc2"
"RootFyc3"
"RootFzb1"
"RootFzb2"
"RootFzb3"
"RootFzc1"
"RootFzc2"
"RootFzc3"
"RootMxb1"
"RootMxb2"
"RootMxb3"
"RootMxc1"
"RootMxc2"
"RootMxc3"
"RootMyb1"
"RootMyb2"
"RootMyb3"
"RootMyc1"
"RootMyc2"
"RootMyc3"
"RootMzb1"
"RootMzb2"
"RootMzb3"
"RootMzc1"
"RootMzc2"
"RootMzc3"
"RotSpeed"
"RotThrust"
"RotTorq"
"Spn1MLxb1"
"Spn1MLyb1"
"Spn2MLxb1"
"Spn2MLyb1"
"Spn3MLxb1"
"Spn3MLyb1"
"Spn4MLxb1"
"Spn4MLyb1"
"Spn5MLxb1"
"Spn5MLyb1"
"Spn6MLxb1"
"Spn6MLyb1"
"Spn7MLxb1"
"Spn7MLyb1"
"Spn8MLxb1"
"Spn8MLyb1"
"Spn9MLxb1"
"Spn9MLyb1"
"TTDspTwst"
"TipDxb1"
"TipDxb2"
"TipDxb3"
"TipDxc1"
"TipDxc2"
"TipDxc3"
"TipDyb1"
"TipDyb2"
"TipDyb3"
"TipDyc1"
"TipDyc2"
"TipDyc3"
"TipDzb1"
"TipDzb2"
"TipDzb3"
"TipDzc1"
"TipDzc2"
"TipDzc3"
"TwHt1TPxi"
"TwHt1TPyi"
"TwrBsFxt"
"TwrBsFyt"
"TwrBsFzt"
"TwrBsMxt"
"TwrBsMyt"
"TwrBsMzt"
"TwstDefl1"
"YawBrFxp"
"YawBrFyp"
"YawBrFzp"
"YawBrMxp"
"YawBrMyp"
"YawBrMzp"
"YawBrTDxt"
"YawBrTDyt"
END of input file (the word "END" must appear in the first 3 columns of this last OutList line)
---------------------- NODE OUTPUTS --------------------------------------------
1 BldNd_BladesOut - Blades to output
99 BldNd_BlOutNd - Blade nodes on each blade (currently unused)
OutList - The next line(s) contains a list of output parameters. See OutListParameters.xlsx, ElastoDyn_Nodes tab for a listing of available output channels, (-)
"TDx" - local flapwise (translational) deflection (relative to the undeflected position) of node
"TDy" - local edgewise (translational) deflection (relative to the undeflected position) of node
"RDz"
END of input file (the word "END" must appear in the first 3 columns of this last OutList line)

[cjking1226]

亲爱的@cjking1226,

正如我们论坛讨论的，你总可以把 ElastoDyn 的平台参考点放在塔顶。从模型中剔除塔。 而且没有YawDOF失效后，舱体将跟随平台移动。 所以，#617可用于规定吊舱的6-DOF运动。

我不确定你的使用场景是否需要规定其他动作，比如旋翼旋转（如果不固定）或叶片螺距，但这些都必须通过控制器来完成。

此致敬意

Dear @jjonkman ,
I suddenly have a very crucial question. I’m using ExtPtfm (CompSub=2) to impose a prescribed platform/tower-top motion for a floating turbine, and my goal is to run Fast.Farm to predict wake deficit. If I disable AeroDyn/ServoDyn (CompAero=0, CompServo=0) and only keep a prescribed rotor speed, will Fast.Farm still produce a physically meaningful wake deficit? Or does Fast.Farm require aerodynamic loads (e.g., thrust/Ct from AeroDyn) from OpenFAST to drive the wake model?
Best regards,

[jjonkman]

Dear @cjking1226,

Summarizing other posts, to place the ElastoDyn platform reference point at the tower-top and eliminate the tower, I would set:
TowerHt = TowerBsHt = PtfmCMzt = PtfmRefzt, disable the tower DOFs (TwFADOF1 = TwFADOF2 = TwSSDOF1 = TwSSDOF2 = FALSE), and set the mass per unit length (TMassDen) in the ElastoDyn tower file to zero. That said, due internal input data consistency checks, ElastoDyn won't allow you to have a zero-length tower with zero mass, so, I would modify these, adding epsilon (a small value greater than zero) to TowerHt and TMassDen.

The matrices and force vector of the external platform (CompSub = 2) are specified with respect to the platform reference point defined in ElastoDyn, i.e., located along the tower centerline at an elevation of PtfmRefzt.

When OpenFAST is coupled to FAST.Farm, AeroDyn or AeroDisk must be enabled to compute wake effects in FAST.Farm. ServoDyn does not need to be enabled in OpenFAST when coupled to FAST.Farm, unless you want to execute individual turbine or super control functions, especially important if GenDOF = TRUE in ElastoDyn.

Best regards,

[cjking1226]

亲爱的@cjking1226,

总结其他帖子，为了将 ElastoDyn 平台的参考点放在塔顶并去掉塔，我会设置： 塔楼=塔楼BsHt=PtfmCMzt=PtfmRefzt，关闭塔的景深 （TwFADOF1=TwFADOF2=TWSSDOF1=TWSSDOF2= FALSE），并设置单位长度的质量（TMassDen）在 ElastoDyn 塔文件中归零。 不过，由于内部输入数据一致性检查，ElastoDyn不允许你拥有零长度且质量为零的塔，所以我会修改这些，加入ε（小于零的值）塔楼以及TMassDen.

外部平台的矩阵和力向量（合成字幕组= 2）相对于ElastoDyn定义的平台参考点指定，即位于塔中心线上、高点为PtfmRefzt.

当OpenFAST与FAST耦合时，必须启用农场、AeroDyn或AeroDisk才能在FAST中计算尾迹效应。农场。 当与 FAST 耦合时，ServoDyn 无需在 OpenFAST 中启用。刷农，除非你想执行单个涡轮或超级控制功能，尤其是如果GenDOF= 在 ElastoDyn 中为真。

此致敬意
Dear @jjonkman ,
Thank you very much for your recent guidance. Following your suggestions, I have implemented the External Platform MCKF approach. With aerodynamics turned off, I am now able to reproduce the prescribed 6-DOF platform motion very accurately.You can look at the screenshot.

My next step is to compute the wake using OpenFAST/FAST.Farm, which requires setting CompInflow = 1 and CompAero = 2. However, in this case the rotor aerodynamics will again generate aerodynamic loads, in addition to the external MCKF loads, so the resulting platform motion may no longer exactly follow the prescribed motion.

Could you please advise how AeroDyn15 should be configured in this situation? In particular, how can aerodynamic loads be handled so that the prescribed platform motion is preserved, while still obtaining a physically meaningful wake? I am also concerned that modifying AeroDyn settings may affect wake fidelity, and would appreciate your guidance on best practice:------- AERODYN v15.03.* INPUT FILE ------------------------------------------------
IEA 15 MW Offshore Reference Turbine
====== General Options ============================================================================
False Echo - Echo the input to ".AD.ech"? (flag)
default DTAero - Time interval for aerodynamic calculations {or "default"} (s)
1 WakeMod - Type of wake/induction model (switch) {0=none, 1=BEMT, 2=DBEMT, 3=OLAF} [WakeMod cannot be 2 or 3 when linearizing]
2 AFAeroMod - Type of blade airfoil aerodynamics model (switch) {1=steady model, 2=Beddoes-Leishman unsteady model} [AFAeroMod must be 1 when linearizing]
0 TwrPotent - Type tower influence on wind based on potential flow around the tower (switch) {0=none, 1=baseline potential flow, 2=potential flow with Bak correction}
0 TwrShadow - Calculate tower influence on wind based on downstream tower shadow (switch) {0=none, 1=Powles model, 2=Eames model}
False TwrAero - Calculate tower aerodynamic loads? (flag)
False FrozenWake - Assume frozen wake during linearization? (flag) [used only when WakeMod=1 and when linearizing]
False CavitCheck - Perform cavitation check? (flag) [AFAeroMod must be 1 when CavitCheck=true]
False Buoyancy - Include buoyancy effects? (flag)
False CompAA - Flag to compute AeroAcoustics calculation [only used when WakeMod=1 or 2]
AeroAcousticsInput.dat AA_InputFile - AeroAcoustics input file [used only when CompAA=true]
====== Environmental Conditions ===================================================================
"default" AirDens - Air density (kg/m^3)
"default" KinVisc - Kinematic air viscosity (m^2/s)
"default" SpdSound - Speed of sound (m/s)
"default" Patm - Atmospheric pressure (Pa) [used only when CavitCheck=True]
"default" Pvap - Vapour pressure of fluid (Pa) [used only when CavitCheck=True]
====== Blade-Element/Momentum Theory Options ====================================================== [used only when WakeMod=1]
2 SkewMod - Type of skewed-wake correction model (switch) {1=uncoupled, 2=Pitt/Peters, 3=coupled} [unused when WakeMod=0 or 3]
default SkewModFactor - Constant used in Pitt/Peters skewed wake model {or "default" is 15/32*pi} (-) [used only when SkewMod=2; unused when WakeMod=0 or 3]
True TipLoss - Use the Prandtl tip-loss model? (flag) [unused when WakeMod=0 or 3]
True HubLoss - Use the Prandtl hub-loss model? (flag) [unused when WakeMod=0 or 3]
True TanInd - Include tangential induction in BEMT calculations? (flag) [unused when WakeMod=0 or 3]
True AIDrag - Include the drag term in the axial-induction calculation? (flag) [unused when WakeMod=0 or 3]
True TIDrag - Include the drag term in the tangential-induction calculation? (flag) [unused when WakeMod=0,3 or TanInd=FALSE]
default IndToler - Convergence tolerance for BEMT nonlinear solve residual equation {or "default"} (-) [unused when WakeMod=0 or 3]
500 MaxIter - Maximum number of iteration steps (-) [unused when WakeMod=0]
====== Dynamic Blade-Element/Momentum Theory Options ====================================================== [used only when WakeMod=1]
2 DBEMT_Mod - Type of dynamic BEMT (DBEMT) model {1=constant tau1, 2=time-dependent tau1} (-) [used only when WakeMod=2]
29.03 tau1_const - Time constant for DBEMT (s) [used only when WakeMod=2 and DBEMT_Mod=1]
====== OLAF -- cOnvecting LAgrangian Filaments (Free Vortex Wake) Theory Options ================== [used only when WakeMod=3]
../IEA-15-240-RWT-OLAF/IEA-15-240-RWT_OLAF.dat OLAFInputFileName - Input file for OLAF [used only when WakeMod=3]
====== Beddoes-Leishman Unsteady Airfoil Aerodynamics Options ===================================== [used only when AFAeroMod=2]
3 UAMod - Unsteady Aero Model Switch (switch) {1=Baseline model (Original), 2=Gonzalez's variant (changes in Cn,Cc,Cm), 3=Minnema/Pierce variant (changes in Cc and Cm)} [used only when AFAeroMod=2]
True FLookup - Flag to indicate whether a lookup for f' will be calculated (TRUE) or whether best-fit exponential equations will be used (FALSE); if FALSE S1-S4 must be provided in airfoil input files (flag) [used only when AFAeroMod=2]
0.1 UAStartRad - Starting radius for dynamic stall (fraction of rotor radius) [used only when AFAeroMod=2]
1.0 UAEndRad - Ending radius for dynamic stall (fraction of rotor radius) [used only when AFAeroMod=2]
====== Airfoil Information =========================================================================
1 AFTabMod - Interpolation method for multiple airfoil tables {1=1D interpolation on AoA (first table only); 2=2D interpolation on AoA and Re; 3=2D interpolation on AoA and UserProp} (-)
1 InCol_Alfa - The column in the airfoil tables that contains the angle of attack (-)
2 InCol_Cl - The column in the airfoil tables that contains the lift coefficient (-)
3 InCol_Cd - The column in the airfoil tables that contains the drag coefficient (-)
4 InCol_Cm - The column in the airfoil tables that contains the pitching-moment coefficient; use zero if there is no Cm column (-)
0 InCol_Cpmin - The column in the airfoil tables that contains the Cpmin coefficient; use zero if there is no Cpmin column (-)
50 NumAFfiles - Number of airfoil files used (-)
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_00.dat" AFNames - Airfoil file names (NumAFfiles lines) (quoted strings)
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_01.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_02.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_03.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_04.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_05.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_06.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_07.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_08.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_09.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_10.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_11.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_12.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_13.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_14.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_15.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_16.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_17.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_18.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_19.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_20.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_21.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_22.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_23.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_24.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_25.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_26.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_27.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_28.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_29.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_30.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_31.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_32.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_33.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_34.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_35.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_36.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_37.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_38.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_39.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_40.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_41.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_42.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_43.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_44.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_45.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_46.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_47.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_48.dat"
"../IEA-15-240-RWT/Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_49.dat"
====== Rotor/Blade Properties =====================================================================
True UseBlCm - Include aerodynamic pitching moment in calculations? (flag)
"../IEA-15-240-RWT/IEA-15-240-RWT_AeroDyn15_blade.dat" ADBlFile(1) - Name of file containing distributed aerodynamic properties for Blade #1 (-)
"../IEA-15-240-RWT/IEA-15-240-RWT_AeroDyn15_blade.dat" ADBlFile(2) - Name of file containing distributed aerodynamic properties for Blade #2 (-) [unused if NumBl < 2]
"../IEA-15-240-RWT/IEA-15-240-RWT_AeroDyn15_blade.dat" ADBlFile(3) - Name of file containing distributed aerodynamic properties for Blade #3 (-) [unused if NumBl < 3]
====== Hub Properties ============================================================================== [used only when Buoyancy=True]
0.0 VolHub - Hub volume (m^3)
0.0 HubCenBx - Hub center of buoyancy x direction offset (m)
====== Nacelle Properties ========================================================================== [used only when Buoyancy=True]
0.0 VolNac - Nacelle volume (m^3)
0,0,0 NacCenB - Position of nacelle center of buoyancy from yaw bearing in nacelle coordinates (m)
====== Tail fin Aerodynamics ========================================================================
False TFinAero - Calculate tail fin aerodynamics model (flag)
"unused" TFinFile - Input file for tail fin aerodynamics [used only when TFinAero=True]
====== Tower Influence and Aerodynamics ============================================================= [used only when TwrPotent/=0, TwrShadow/=0, or TwrAero=True]
0 NumTwrNds - Number of tower nodes used in the analysis (-) [used only when TwrPotent/=0, TwrShadow/=0, or TwrAero=True]
TwrElev TwrDiam TwrCd TwrTI TwrCb !TwrTI used only with TwrShadow=2, TwrCb used only with Buoyancy=True
(m) (m) (-) (-) (-)
====== Outputs ====================================================================================
False SumPrint - Generate a summary file listing input options and interpolated properties to ".AD.sum"? (flag)
9 NBlOuts - Number of blade node outputs [0 - 9] (-)
6, 11, 16, 21, 25, 30, 35, 40, 45 BlOutNd - Blade nodes whose values will be output (-)
0 NTwOuts - Number of tower node outputs [0 - 9] (-)
0 TwOutNd - Tower nodes whose values will be output (-)
OutList - The next line(s) contains a list of output parameters. See OutListParameters.xlsx for a listing of available output channels, (-)
"RtFldFxh"
"RtFldFyh"
"RtFldFzh"
"RtFldMxh"
"RtFldMyh"
"RtFldMzh"
"RtVAvgxh"
"RtFldCp"
"RtFldCt"
"RtArea"
"RtSpeed"
"RtTSR"
END of input file (the word "END" must appear in the first 3 columns of this last OutList line)
====== Outputs for all blade stations (same ending as above for B1N1.... =========================== [optional section]
1 BldNd_BladesOut - Number of blades to output all node information at. Up to number of blades on turbine. (-)
"All" BldNd_BlOutNd - Future feature will allow selecting a portion of the nodes to output. Not implemented yet. (-)
OutList - The next line(s) contains a list of output parameters. See OutListParameters.xlsx for a listing of available output channels, (-)
Vrel
Alpha
Vindx
Vindy
Cn
Ct
Fn
Ft
Fx
Fy
TnInd
AxInd
END (the word "END" must appear in the first 3 columns of this last OutList line in the optional nodal output section)

[jjonkman]

Dear @cjking1226,

As discussed in issue #617, the key to preserve the motion time history that want to prescribe in the presence of other loads (like aerodynamic applied loads), is to use a very high platform mass/inertia, and associated stiffness/damping/load. Effectively, as long as the aerodynamic applied loads are much much smaller than the platform loads, the platform motion will be dominated by the platform loads. You haven't said what high platform mass/inertia, and associated stiffness and damping you are using, but that is the key.

Best regards,