Wave Disturbance Input Gains

Hi all
I need to know where can I find the disturbance input matrix which describes the gains between the states and the wave disturbance (HD Extended input: wave elevation at platform ref point, m) in the linearized file (*.lin). It is always equal to a column of zeros. How can I deviate the values away from zeros?
Thanks
M.Fekry

Dear Mohamed,

Can you clarify your question? Are you saying that the input matrix (B) is always zero even when you’ve enabled PotMod = 1 with ExctnMod = 2 in HydroDyn when linearizing OpenFAST?

Best regards,

Dear Dr Jason.Jonkman
The setting for the parametrs is PotMod = 1 with ExctnMod = 0 in HydroDyn file which generates zeros column in B matrix.
if I changed it to PotMod = 1 with ExctnMod = 2, The following error occurs:

[code] Setting WaveTMax to 0.0 since WaveMod = 0
Reading in WAMIT output with root name “…/5MW_Baseline/HydroData/Spar”.
Computing radiation impulse response functions and wave diffraction forces.

FAST_InitializeAll:HydroDyn_Init:WAMIT_Init:SS_Exc_Init:OpenFInpFile:The input file,
“…/5MW_Baseline/HydroData/Spar.ssexctn”, was not found.

FAST encountered an error during module initialization.
Simulation error level: FATAL ERROR

Aborting OpenFAST.[/code]
The HydroDyn file which generats this error:

[code]------- HydroDyn v2.03.* Input File --------------------------------------------
NREL 5.0 MW offshore baseline floating platform HydroDyn input properties for the OC3 Hywind.
False Echo - Echo the input file data (flag)
---------------------- ENVIRONMENTAL CONDITIONS --------------------------------
1025 WtrDens - Water density (kg/m^3)
320 WtrDpth - Water depth (meters)
0 MSL2SWL - Offset between still-water level and mean sea level (meters) [positive upward; unused when WaveMod = 6; must be zero if PotMod=1 or 2]
---------------------- WAVES ---------------------------------------------------
0 WaveMod - Incident wave kinematics model {0: none=still water, 1: regular (periodic), 1P#: regular with user-specified phase, 2: JONSWAP/Pierson-Moskowitz spectrum (irregular), 3: White noise spectrum (irregular), 4: user-defined spectrum from routine UserWaveSpctrm (irregular), 5: Externally generated wave-elevation time series, 6: Externally generated full wave-kinematics time series [option 6 is invalid for PotMod/=0]} (switch)
0 WaveStMod - Model for stretching incident wave kinematics to instantaneous free surface {0: none=no stretching, 1: vertical stretching, 2: extrapolation stretching, 3: Wheeler stretching} (switch) [unused when WaveMod=0 or when PotMod/=0]
3630 WaveTMax - Analysis time for incident wave calculations (sec) [unused when WaveMod=0; determines WaveDOmega=2Pi/WaveTMax in the IFFT]
0.25 WaveDT - Time step for incident wave calculations (sec) [unused when WaveMod=0; 0.1<=WaveDT<=1.0 recommended; determines WaveOmegaMax=Pi/WaveDT in the IFFT]
6 WaveHs - Significant wave height of incident waves (meters) [used only when WaveMod=1, 2, or 3]
10 WaveTp - Peak-spectral period of incident waves (sec) [used only when WaveMod=1 or 2]
“DEFAULT” WavePkShp - Peak-shape parameter of incident wave spectrum (-) or DEFAULT (string) [used only when WaveMod=2; use 1.0 for Pierson-Moskowitz]
0 WvLowCOff - Low cut-off frequency or lower frequency limit of the wave spectrum beyond which the wave spectrum is zeroed (rad/s) [unused when WaveMod=0, 1, or 6]
500 WvHiCOff - High cut-off frequency or upper frequency limit of the wave spectrum beyond which the wave spectrum is zeroed (rad/s) [unused when WaveMod=0, 1, or 6]
0 WaveDir - Incident wave propagation heading direction (degrees) [unused when WaveMod=0 or 6]
0 WaveDirMod - Directional spreading function {0: none, 1: COS2S} (-) [only used when WaveMod=2,3, or 4]
1 WaveDirSpread - Wave direction spreading coefficient ( > 0 ) (-) [only used when WaveMod=2,3, or 4 and WaveDirMod=1]
1 WaveNDir - Number of wave directions (-) [only used when WaveMod=2,3, or 4 and WaveDirMod=1; odd number only]
90 WaveDirRange - Range of wave directions (full range: WaveDir +/- 1/2*WaveDirRange) (degrees) [only used when WaveMod=2,3,or 4 and WaveDirMod=1]
123456789 WaveSeed(1) - First random seed of incident waves [-2147483648 to 2147483647] (-) [unused when WaveMod=0, 5, or 6]
RANLUX WaveSeed(2) - Second random seed of incident waves [-2147483648 to 2147483647] for intrinsic pRNG, or an alternative pRNG: “RanLux” (-) [unused when WaveMod=0, 5, or 6]
TRUE WaveNDAmp - Flag for normally distributed amplitudes (flag) [only used when WaveMod=2, 3, or 4]
“” WvKinFile - Root name of externally generated wave data file(s) (quoted string) [used only when WaveMod=5 or 6]
1 NWaveElev - Number of points where the incident wave elevations can be computed (-) [maximum of 9 output locations]
0 WaveElevxi - List of xi-coordinates for points where the incident wave elevations can be output (meters) [NWaveElev points, separated by commas or white space; usused if NWaveElev = 0]
0 WaveElevyi - List of yi-coordinates for points where the incident wave elevations can be output (meters) [NWaveElev points, separated by commas or white space; usused if NWaveElev = 0]
---------------------- 2ND-ORDER WAVES ----------------------------------------- [unused with WaveMod=0 or 6]
FALSE WvDiffQTF - Full difference-frequency 2nd-order wave kinematics (flag)
FALSE WvSumQTF - Full summation-frequency 2nd-order wave kinematics (flag)
0 WvLowCOffD - Low frequency cutoff used in the difference-frequencies (rad/s) [Only used with a difference-frequency method]
3.5 WvHiCOffD - High frequency cutoff used in the difference-frequencies (rad/s) [Only used with a difference-frequency method]
0.1 WvLowCOffS - Low frequency cutoff used in the summation-frequencies (rad/s) [Only used with a summation-frequency method]
3.5 WvHiCOffS - High frequency cutoff used in the summation-frequencies (rad/s) [Only used with a summation-frequency method]
---------------------- CURRENT ------------------------------------------------- [unused with WaveMod=6]
0 CurrMod - Current profile model {0: none=no current, 1: standard, 2: user-defined from routine UserCurrent} (switch)
0 CurrSSV0 - Sub-surface current velocity at still water level (m/s) [used only when CurrMod=1]
“DEFAULT” CurrSSDir - Sub-surface current heading direction (degrees) or DEFAULT (string) [used only when CurrMod=1]
20 CurrNSRef - Near-surface current reference depth (meters) [used only when CurrMod=1]
0 CurrNSV0 - Near-surface current velocity at still water level (m/s) [used only when CurrMod=1]
0 CurrNSDir - Near-surface current heading direction (degrees) [used only when CurrMod=1]
0 CurrDIV - Depth-independent current velocity (m/s) [used only when CurrMod=1]
0 CurrDIDir - Depth-independent current heading direction (degrees) [used only when CurrMod=1]
---------------------- FLOATING PLATFORM --------------------------------------- [unused with WaveMod=6]
1 PotMod - Potential-flow model {0: none=no potential flow, 1: frequency-to-time-domain transforms based on WAMIT output, 2: fluid-impulse theory (FIT)} (switch)
“…/5MW_Baseline/HydroData/Spar” PotFile - Root name of potential-flow model data; WAMIT output files containing the linear, nondimensionalized, hydrostatic restoring matrix (.hst), frequency-dependent hydrodynamic added mass matrix and damping matrix (.1), and frequency- and direction-dependent wave excitation force vector per unit wave amplitude (.3) (quoted string) [MAKE SURE THE FREQUENCIES INHERENT IN THESE WAMIT FILES SPAN THE PHYSICALLY-SIGNIFICANT RANGE OF FREQUENCIES FOR THE GIVEN PLATFORM; THEY MUST CONTAIN THE ZERO- AND INFINITE-FREQUENCY LIMITS!]
1 WAMITULEN - Characteristic body length scale used to redimensionalize WAMIT output (meters) [only used when PotMod=1]
8029.21 PtfmVol0 - Displaced volume of water when the platform is in its undisplaced position (m^3) [only used when PotMod=1; USE THE SAME VALUE COMPUTED BY WAMIT AS OUTPUT IN THE .OUT FILE!]
0 PtfmCOBxt - The xt offset of the center of buoyancy (COB) from the platform reference point (meters) [only used when PotMod=1]
0 PtfmCOByt - The yt offset of the center of buoyancy (COB) from the platform reference point (meters) [only used when PotMod=1]
2 ExctnMod - Wave Excitation model {0: None, 1: DFT, 2: state-space} (switch) [only used when PotMod=1; STATE-SPACE REQUIRES *.ssexctn INPUT FILE]
0 RdtnMod - Radiation memory-effect model {0: no memory-effect calculation, 1: convolution, 2: state-space} (switch) [only used when PotMod=1; STATE-SPACE REQUIRES *.ss INPUT FILE]
60 RdtnTMax - Analysis time for wave radiation kernel calculations (sec) [only used when PotMod=1 and RdtnMod>0; determines RdtnDOmega=Pi/RdtnTMax in the cosine transform; MAKE SURE THIS IS LONG ENOUGH FOR THE RADIATION IMPULSE RESPONSE FUNCTIONS TO DECAY TO NEAR-ZERO FOR THE GIVEN PLATFORM!]
“DEFAULT” RdtnDT - Time step for wave radiation kernel calculations (sec) [only used when PotMod=1 and RdtnMod=1; DT<=RdtnDT<=0.1 recommended; determines RdtnOmegaMax=Pi/RdtnDT in the cosine transform]
---------------------- 2ND-ORDER FLOATING PLATFORM FORCES ---------------------- [unused with WaveMod=0 or 6, or PotMod=0 or 2]
0 MnDrift - Mean-drift 2nd-order forces computed {0: None; [7, 8, 9, 10, 11, or 12]: WAMIT file to use} [Only one of MnDrift, NewmanApp, or DiffQTF can be non-zero]
0 NewmanApp - Mean- and slow-drift 2nd-order forces computed with Newman’s approximation {0: None; [7, 8, 9, 10, 11, or 12]: WAMIT file to use} [Only one of MnDrift, NewmanApp, or DiffQTF can be non-zero. Used only when WaveDirMod=0]
0 DiffQTF - Full difference-frequency 2nd-order forces computed with full QTF {0: None; [10, 11, or 12]: WAMIT file to use} [Only one of MnDrift, NewmanApp, or DiffQTF can be non-zero]
0 SumQTF - Full summation -frequency 2nd-order forces computed with full QTF {0: None; [10, 11, or 12]: WAMIT file to use}
---------------------- FLOATING PLATFORM FORCE FLAGS -------------------------- [unused with WaveMod=6]
True PtfmSgF - Platform horizontal surge translation force (flag) or DEFAULT
True PtfmSwF - Platform horizontal sway translation force (flag) or DEFAULT
True PtfmHvF - Platform vertical heave translation force (flag) or DEFAULT
True PtfmRF - Platform roll tilt rotation force (flag) or DEFAULT
True PtfmPF - Platform pitch tilt rotation force (flag) or DEFAULT
True PtfmYF - Platform yaw rotation force (flag) or DEFAULT
---------------------- PLATFORM ADDITIONAL STIFFNESS AND DAMPING --------------
0 0 0 0 0 0 AddF0 - Additional preload (N, N-m)
0 0 0 0 0 0 AddCLin - Additional linear stiffness (N/m, N/rad, N-m/m, N-m/rad)
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 98340000
100000 0 0 0 0 0 AddBLin - Additional linear damping(N/(m/s), N/(rad/s), N-m/(m/s), N-m/(rad/s))
0 100000 0 0 0 0
0 0 130000 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 13000000
0 0 0 0 0 0 AddBQuad - Additional quadratic drag(N/(m/s)^2, N/(rad/s)^2, N-m(m/s)^2, N-m/(rad/s)^2)
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
---------------------- AXIAL COEFFICIENTS --------------------------------------
1 NAxCoef - Number of axial coefficients (-)
AxCoefID AxCd AxCa AxCp
(-) (-) (-) (-)
1 0.00 0.00 1.00
---------------------- MEMBER JOINTS -------------------------------------------
4 NJoints - Number of joints (-) [must be exactly 0 or at least 2]
JointID Jointxi Jointyi Jointzi JointAxID JointOvrlp [JointOvrlp= 0: do nothing at joint, 1: eliminate overlaps by calculating super member]
(-) (m) (m) (m) (-) (switch)
1 0.00000 0.00000 -120.00000 1 0
2 0.00000 0.00000 -12.00000 1 0
3 0.00000 0.00000 -4.00000 1 0
4 0.00000 0.00000 10.00000 1 0
---------------------- MEMBER CROSS-SECTION PROPERTIES -------------------------
2 NPropSets - Number of member property sets (-)
PropSetID PropD PropThck
(-) (m) (m)
1 9.40000 0.00010
2 6.50000 0.00010
---------------------- SIMPLE HYDRODYNAMIC COEFFICIENTS (model 1) --------------
SimplCd SimplCdMG SimplCa SimplCaMG SimplCp SimplCpMG SimplAxCa SimplAxCaMG SimplAxCp SimplAxCpMG
(-) (-) (-) (-) (-) (-) (-) (-) (-) (-)
0.60 0.00 0.00 0.00 1.00 1.00 1.00 1.00 1.00 1.00
---------------------- DEPTH-BASED HYDRODYNAMIC COEFFICIENTS (model 2) ---------
0 NCoefDpth - Number of depth-dependent coefficients (-)
Dpth DpthCd DpthCdMG DpthCa DpthCaMG DpthCp DpthCpMG DpthAxCa DpthAxCaMG DpthAxCp DpthAxCpMG
(m) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-)
---------------------- MEMBER-BASED HYDRODYNAMIC COEFFICIENTS (model 3) --------
0 NCoefMembers - Number of member-based coefficients (-)
MemberID MemberCd1 MemberCd2 MemberCdMG1 MemberCdMG2 MemberCa1 MemberCa2 MemberCaMG1 MemberCaMG2 MemberCp1 MemberCp2 MemberCpMG1 MemberCpMG2 MemberAxCa1 MemberAxCa2 MemberAxCaMG1 MemberAxCaMG2 MemberAxCp1 MemberAxCp2 MemberAxCpMG1 MemberAxCpMG2
(-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-)
-------------------- MEMBERS -------------------------------------------------
3 NMembers - Number of members (-)
MemberID MJointID1 MJointID2 MPropSetID1 MPropSetID2 MDivSize MCoefMod PropPot [MCoefMod=1: use simple coeff table, 2: use depth-based coeff table, 3: use member-based coeff table] [ PropPot/=0 if member is modeled with potential-flow theory]
(-) (-) (-) (-) (-) (m) (switch) (flag)
1 1 2 1 1 0.5000 1 TRUE
2 2 3 1 2 0.5000 1 TRUE
3 3 4 2 2 0.5000 1 TRUE
---------------------- FILLED MEMBERS ------------------------------------------
0 NFillGroups - Number of filled member groups (-) [If FillDens = DEFAULT, then FillDens = WtrDens; FillFSLoc is related to MSL2SWL]
FillNumM FillMList FillFSLoc FillDens
(-) (-) (m) (kg/m^3)
---------------------- MARINE GROWTH -------------------------------------------
0 NMGDepths - Number of marine-growth depths specified (-)
MGDpth MGThck MGDens
(m) (m) (kg/m^3)
---------------------- MEMBER OUTPUT LIST --------------------------------------
0 NMOutputs - Number of member outputs (-) [must be < 10]
MemberID NOutLoc NodeLocs [NOutLoc < 10; node locations are normalized distance from the start of the member, and must be >=0 and <= 1] [unused if NMOutputs=0]
(-) (-) (-)
---------------------- JOINT OUTPUT LIST ---------------------------------------
0 NJOutputs - Number of joint outputs [Must be < 10]
0 JOutLst - List of JointIDs which are to be output (-)[unused if NJOutputs=0]
---------------------- OUTPUT --------------------------------------------------
True HDSum - Output a summary file [flag]
False OutAll - Output all user-specified member and joint loads (only at each member end, not interior locations) [flag]
2 OutSwtch - Output requested channels to: [1=Hydrodyn.out, 2=GlueCode.out, 3=both files]
“E15.7e2” OutFmt - Output format for numerical results (quoted string) [not checked for validity!]
“A11” OutSFmt - Output format for header strings (quoted string) [not checked for validity!]
---------------------- OUTPUT CHANNELS -----------------------------------------
“Wave1Elev” - Wave elevation at the platform reference point (0, 0)

END of output channels and end of file. (the word “END” must appear in the first 3 columns of this line)
[/code]

Where I can find Spar.ssexctn file or how to solve this issue?

Best Regards

Dear Mohamed,

The state-space wave-excitation data (*.ssexctn) file can be generated by the SS_Excitation_Fitting toolbox, which is similar to the MATLAB-based SS_Fitting toolbox for wave-radiation (github.com/OpenFAST/openfast/issues/397, where it suggests reaching out to Alan Wright for access to the toolbox. That is still my recommendation.

Best regards,

Dear Dr Jason.Jonkman
Thanks for your response. I will reach out to Alan Wright.
Regards
M.Fekry

Dear Dr Jason.Jonkman,
I have generated the hydrodynamic coefficient file of the wamit format file myself, but I encountered the following problems during operation. I would like to ask which file (.1.3.hst) has the problem and how to modify it?


Best regards,

Dear @Hairui.Jiang,

The wave period and direction are specified within the WAMIT *.3 file containing the wave-excitation coefficients associated with incident waves.

Best regards,

Dear Dr Jason.Jonkman,
Thank you for your reply. Another question is the .hst file. I get multiple sets of hydrostatic stiffness coefficient matrices by setting different frequencies (or wave directions). How can I select the appropriate hydrostatic stiffness matrix as the .hst file? I browse the help file and found that the .hst file is not frequency dependent does that mean that the .hst file is not that important when calculating a first-order problem.Last question is how do I match the wave period and direction of the .3 file to the wave period and direction I set in FAST(HydroDyn) so that the following error will not occur.

Best regards,

Dear @Hairui.Jiang,

A first-order hydrostatics solution should involve the calculation of buoyancy of the body for small displacements in the still water condition. So, the data in the *.hst file should not depend on wave frequency or direction.

An error about

reading period and direction from WAMIT file

would be caused by an improperly formatted *.3 file. You mentioned that you’ve generated this file yourself; I would check that the file is formatted properly (e.g., that it matches the format of the sample *.3 files provided in the OpenFAST r-test: r-test/glue-codes/openfast/5MW_Baseline/HydroData at main · OpenFAST/r-test · GitHub).

Best regards,

Dear Dr Jason.Jonkman,
Thank you for your reply, I’m sorry I didn’t elaborate on my problem, my problem is when I generate .3 files with a frequency of 0.01-0.4rad/s, that error occurs(reading period and direction from WAMIT file), but when I generate 0.4-1rad /s, it works fine, I want to know how FAST matches the .3 files I generate at different frequencies.
Best regards,

Dear @Hairui.Jiang,

You can review how HydroDyn is reading the *.3 data file by reviewing the HydroDyn source code. As of OpenFAST v3.1 main, the error you are referring to is generated on line 695 of WAMIT.f90: openfast/WAMIT.f90 at main · OpenFAST/openfast · GitHub.

Best regards,