SIMO Standalone Release Notes
In the following, changes that are only relevant to standalone use of
SIMO
is listed. For a complete list of changes, please also refer to
the SIMA
release notes.
SIMO 4.26.0 (20230612)
Initial release of SIMO
4.26.
SIMO 4.26.0 Input changes
Input files used in version 4.24 can be used unchanged with the following exceptions:

Airfoil coefficient library are no longer given to
WIND TURBine SPECification
andVERTical AXIS TURBine
, but once on the top level of the sysfile. See here for more details.
SIMO licensing
SIMO
is licensemanaged using the FLEXlm / FLEXlnet software license
management system. If you want SIMO
to be used from any networked
computer on your site, you must run a license manager on a server in
your network. Alternatively, SIMO
may be run on a single computer
using a standalone license file.
Please note that version 4.2 and higher requires a licence file with a feature version that is equal or larger than the link date.
In order to issue a server license or a standalone license file, SINTEF Ocean or DNV GL needs the following info on your server:

License type (server or standalone)

Operating system and version (Windows 10, Windows 7 and Linux currently supported)

MAC address / FLEXlm hosted of the computer.
Your ITstaff is probably already familiar with this procedure as FLEXlm is used by a large number of other applications (e.g. Matlab).
SIMO version numbers
The version number consists of three numbers separated by periods, e.g. 4.16.0. The two first are the version. The third is updated for each subsequent (bug fix) release.
Even numbered versions, e.g. 4.14, 4.16, are reserved for official versions.
Odd numbered versions, e.g. 4.15, 4.17, are reserved for development versions. The next official release will therefore be 4.26.
SIMO 4.22.0 (20220225)
Initial release of SIMO
4.22.
SIMO 4.22.0 Input changes
Apart from the notes below, input files used in version 4.20 can be used unchanged.
Direction Indices for Quadratic Transfer Functions
For quadratic transfer functions where NDQTF2=1 SIMO
did previously
require IDQTF2 = 1 for all coefficients. This has been changed so that
now IDQTF2 must always be equal to IDQTF1.
To use old input files, the values for IDQTF2 must be updated accordingly.
SIMO 4.20.0 (20210407)
Initial internal release of SIMO
4.20.
SIMO 4.20.0 Removed functionality
No previously available functionality have been removed in this version.
SIMO 4.20.0 Deprecated functionality
The use of SIMO
INPMOD
is deprecated. The application will be
removed in the next major release of Simo. If you’re using any Simo
INPMOD functionality please contact Software Support and we will find an
alternative solution for you.
The Nonlinear Buoyancy Correction functionality is deprecated and will be removed in the next version. Please use Nonlinear Hydrostatic Stiffness instead.
The old thruster specification (THRUST
) and the old DP model
(DYNAMIC POSITIONING SYSTEM
) are deprecated and will be removed in a
future version of SIMO
.
SIMO 4.18.2 (20201111)
Bugfix release of SIMO
4.18
SIMO 4.18.2 Corrected errors
Airfoils with userspecified stall points
An error resulted in airfoils with userspecified stall points always operating in dynamic stall. This has been corrected.
Error since SIMO version 4.6.0
Fixed wrong mirroring of wave drift damping coefficients when geometric symmetry is present
When the body geometry is symmetric about the X=0 and/or Y=0 planes, SIMO offers the possibility to mirror wave drift damping coefficients to wave headings not present in the input based on symmtry relations. These symmtry relations was wrongly implemented resulting in wrong sign on some of the damping matrix entries. The error has now been corrected.
Longstanding error
Unnessecary restriction on wave drift damping removed
Previously, it was not allowed to provide frequency dependent wave drift damping coefficients (Newmans method) when wave drift coefficients was not provided. This is relevant in cases where wave drift damping coefficients is used in combination with a full QTF. This restriction has now been removed.
Longstanding error
Turret initial angle
Fixed an issue related to the initial yaw angle of a turret body. Before the fix, the initial angle was interpreted as a relative angle (relative to the master) in the static analysis, and as a global yaw angle in the dynamic analysis. Now, the intial angle is interpreted as a global yaw angle in both static and dynamic analysis. The documentation has also been clarified. In relation to this, a modification of the static analysis is implemented such that the friction of the turret is turned off during the search for static equilibrium.
Another issue related to the turret body has also been fixed. Before, the turret body could have sudden "jumps" in yaw angle when the yaw angle of the master body crosses the angle (+/) 180 degrees. These jumps are now avoided.
Error since SIMO version 4.12.0
Wrong sign of products of inertia in user manual
The sign of the products of inertia as documented in the user manual was not consistent with the implementation. Moreover, the sign of the products of inertia in the mass mastrix as written to the prs.lis file was not consistent with the implementation. Now, the sign is flipped in the documentation and in the mass matrix written to the prs.lis file. The simulation results are not affected.
Airfoil identifiers
The maximum length of airfoil identifiers was not consistent in code and documentation. The maximum length was 8 characters and not 64 as described in the airfoil library file description. Long identifiers were truncated to 8 characters. This could result in the wrong airfoil being used in the analyses.
The length is now increased and standardized to 32 characters in both SIMO and RIFLEX.
Also, a potential error that could cause data to be overwritten when reading the airfoil library file has been corrected. This error has not been observed.
SIMO 4.18.0 (20200323)
Initial release of SIMO
4.18.0
SIMO 4.18.0 New / improved functionality
Computation of wind velocity from parametric wind spectra at multiple locations
A new option to specify a vertical domain for computing wind velocity in has been added to account for vertical variation spectral density when computing wind velocity at multiple locations during timedomain simulation.
This option should be considered when using parametric wind spectra and the following features:

Wind forces acting on slender elements

Wind turbine
See the section Environment specification in the Userguide and the section Wind in the theory manual for further details.
Interpolation and extrapolation of airfoil coefficients
Airfoil coefficients may now be given for a single Reynolds number. They will then be used for all Reynolds numbers.
Extrapolation outside the range of Reynolds values given will now be allowed. The value for the closest Reynolds number will be used; i.e. flat extrapolation.
SIMO 4.18.0 Corrected errors
Issues with parameterized wind spectra
The issues with parameterized wind spectra has now been resolved (see previous release notes).
See also release note for the new functionality Computation of wind velocity from parametric wind spectra at multiple locations.
Error since SIMO version 4.2.
Error in DP system guidance mode for vessels outside global origin
A bug has been fixed in the DP system guidance mode. Previously the initial reference position was set at global origin which meant that vessels starting guidance mode outside global origin would not follow the desired path.
Longstanding error.
Airfoil library file with airfoil geometry
Allow SIMO to read airfoil library files that include airfoil geometry. This has previously caused SIMO to fail.
Longstanding error.
Printing error in labels describing presented rotational acceleration
Incorrect naming of rotational accelerations in result presentations have been corrected. It is rotational accelerations that are presented and not double derivative of Euler angles as was incorrectly reported in previous versions.
Longstanding error.
SIMO 4.16.4 (20200303)
Bugfix release with minor improvements.
SIMO 4.16.4 Corrected errors
Error in DP system guidance mode for vessels outside global origin
A bug has been fixed in the DP system guidance mode. Previously the initial reference position was set at global origin which meant that vessels starting guidance mode outside global origin would not follow the desired path.
Longstanding error.
SIMO 4.16.3 (2020????)
Bugfix release with minor improvements.
SIMO 4.16.3 New / improved functionality
Interpolation and extrapolation of airfoil coefficients
Airfoil coefficients may now be given for a single Reynolds number. They will then be used for all Reynolds numbers.
Extrapolation outside the range of Reynolds values given will now be allowed. The value for the closest Reynolds number will be used; i.e. flat extrapolation.
SIMO 4.16.0 (20190506)
SIMO licensing
SIMO
is licensemanaged using the FLEXlm / FLEXlnet software license
management system. If you want SIMO
to be used from any networked
computer on your site, you must run a license manager on a server in
your network. Alternatively, SIMO
may be run on a single computer
using a standalone license file.
Please note that version 4.2 and higher requires a licence file with a feature version that is equal or larger than the link date.
In order to issue a server license or a standalone license file, SINTEF Ocean or DNV GL needs the following info on your server:

License type (server or standalone)

Operating system and version (Windows 7, Windows XP, HPUX and Linux currently supported)

MAC address / FLEXlm hosted of the computer.
Your ITstaff is probably already familiar with this procedure as FLEXlm is used by a large number of other applications (e.g. Matlab).
SIMO version numbers
The version number consists of three numbers separated by periods, e.g. 4.16.0. The two first are the version. The third is updated for each subsequent (bug fix) release.
Even numbered versions, e.g. 4.14, 4.16, are reserved for official versions.
Odd numbered versions, e.g. 4.15, 4.17, are reserved for development versions. The next official release will therefore be 4.18.
SIMO 4.14.0 (20181101)
SIMO 4.12.0
SIMO 4.12.0 New / improved functionality
Gust wind normal to main wind direction with state space wind model
The state space wind model now supports using the Simiu wind spectrum for simulating wind with gusts normal to the main wind direction.
New stationary uniform wind with shear
Wind type 14, stationary uniform wind with shear, has been added. A power or logarithmic shear profile may be specified.
This wind type differs from wind type 10, stationary uniform wind with shear, values interpolated at grid points, in that the shear profile is used directly.
A new simple turret model based on articulated structures
A new turret model is implemented in SIMO
. The functionality enables
modeling of a turret as an articulated structure with freerotation
around vertical axis (Z). The vessel is considered as the master and
turret as the slave. The model also provides simple locking and sliding
through "maximum lock angle" and "slip angle" options. See
Articulated Structures
section in user manual for more details.”
SIMO 4.12.0 Corrected errors
Incorrect calculation of wind speed for some wind types
A bug has been fixed where the wind speed used to calculate force from quadratic wind coefficients was incorrect. This applies when the following wind types was used in combination with quadratic wind coefficients:

Stationary uniform wind with shear

Fluctuating uniform 2component wind

Fluctuating 3component wind read from files (IECWind format)

Fluctuating 3component wind read from files (TurbSim format)
Previously the body zposition was used to determine the wind speed used in the force calculation while the reference height for the wind coefficient should have been used.
Corrected in SIMO
4.10.1.
Correction of notchfilter in PID controller when heading passes +180 deg
A bug has been fixed where the notch filter gave incorrect large differences between estimated and real heading when the real heading passed +180 deg.
Incorrect input for fixed direction thrusters
When giving input to fixed direction thrusters the NDIR
parameter
would have to be given, even though the manual states that this
parameter is intended for rotatable thrusters. This has now been fixed.
As a result, old input files using fixed direction thrusters need to be
updated by removing this parameter.
Wind turbine equipped with one foil blade
An error correction has been done to SIMO wind turbine to prevent program termination if the turbine is only equipped with one blade.
Corrected in SIMO
4.10.4.
Correct possible error in array size for time series
Avoid possible overflow during calculation of the optimal division of
time series into sequences. The error was observed for very large
systems with long time series and could cause incorrect array dimensions
and error termination before the dynamic simulation in SIMO
or in
RIFLEX
for coupled analysis.
Corrected in SIMO
4.10.2.
SIMO 4.12.0 Known issues
Incorrect calculation of wind speeds for bodies with wind coefficients
SIMO
will in some situations calculate wind speed based on an
incorrect wind spectrum for bodies with wind coefficients. This depends
on the choice of wind spectrum type, the wind spectrum reference height
and the wind coefficients reference height.
If default values are used for both wind coefficients and spectrum reference heights (both default values are 10 m) the calculated wind speed will always be correct.
If nondefault values are used some spectra will give incorrect wind speeds:
Case / Wind Type:  Gust wind  Davenport  Harris  Wills 

Wind coefficients reference height = 10 m 
Ok* 
Ok 
Ok 
Ok 
Wind coefficients reference height != 10 m 
Incorrect** 
Ok 
Ok 
Ok 
Case / Wind Type:  Sletringen  ISO 199011 (NPD)  API 

Wind coefficients reference height = 10 m 
Ok* 
Ok 
Ok 
Wind coefficients reference height != 10 m 
Incorrect** 
Incorrect 
Ok 
*) ONLY if wind spectrum reference height is 10 m (default)
**) unless wind spectrum reference height is set to the same value as the wind coefficients reference height
Incorrect calculation of wind speeds for bodies with slender elements
SIMO
will in some situations calculate wind speed based on an
incorrect wind spectrum for bodies that has slender elements with wind
drag coefficients. This depends on the choice of wind spectrum type, the
wind spectrum reference height and the vertical position of the slender
elements:
Case / Wind Type:  Gust wind  Davenport  Harris  Wills 

Slender element global zposition = 10 m 
Ok* 
Ok 
Ok 
Ok 
Slender element global zposition != 10 m 
Incorrect** 
Ok 
Ok 
Ok 
Case / Wind Type:  Sletringen  ISO 199011 (NPD)  API 

Slender element global zposition = 10 m 
Ok* 
Ok 
Ok 
Slender element global zposition != 10 m 
Incorrect** 
Incorrect spectrum 
Ok 
*) ONLY if wind spectrum reference height is 10 m (default)
**) unless wind spectrum reference height is set to the same zvalue
SIMO 4.12.0 Input changes
The following changes must be made to input files used in version 4.10:
 The NDIR
parameter must be removed for fixed direction thrusters.
SIMO 4.10
SIMO 4.10.0 Input changes
The following changes must be made to input files used in version 4.8: 
Bodies of body type 1 must now specify a method for separating wave
frequency and low frequency motions during the simulation  Macro files
for STAMOD
must be updated due to the new equilibrium solver and new
options regarding global elimination of degrees of freedom  Macro files
for DYNMOD
, S2XMOD
and OUTMOD
must be updated due to changes in
the structure of position results  The parameters IMAXTH
and THRMAX
should be removed from system description files with dynamic positioning
systems
SIMO 4.10.0 Corrected errors
Distributed aerodynamic element forces
An error in load moments caused by wind forces acting on slender elements and fixed bodies has been corrected. The error has been present since 4.2.0. In addition, the wind drag force has been calculated from the wind velocity only. The relative velocity is now used in the wind drag calculation.
SIMO 4.10.0 New / improved functionality
Separation of wave frequency motions when using wave force transfer functions
A method for estimating wave frequency and low frequency motions when using body type 1 (wave force transfer functions) has been added. This is in particular important to consider when using cosine series waves and when simulating a turrent moored ships.
The method utilises a 2nd order Butterworth low pass filter in order to estimate the low frequency motion from the total motion during simulation. For more details see Separation of wave frequency and low frequency motions for body type 1 in the user guide.
Change in structure of position time series
The following change break compatibility with macro files used by older
versions of DYNMOD
, S2XMOD
and OUTMOD
. Macro files need to be
updated in order to be used with new versions of SIMO
.
Time series of total and low frequent position are now always stored for
bodies of body type 1 (wave force transfer functions) and body type 2
(wave motion transfer functions). This means that DYNMOD
macro files
that specify storage of results must be updated before they can be run
in newer versions.
Users of S2XMOD
and/or OUTMOD
should note that the content of
responses 29 and 33 has changed and macro files need to be updated to
accomodate this change. Starting with version 4.10.0 the content of
these responses are the same for all bodies regardless of type. The
table below summarises the content of the relevant responses before and
after this change.
Response Number  Body Type  Before 4.10.0  4.10.0 and later 

29 
1 
Total position 
Total position 
2 
LF position 
Total position 

3 and 4 
Total position 
Total position 

33 
1 
N/A 
LF position 
2 
Total position 
LF position 

3 and 4 
N/A 
N/A 
New static equilibrium calculation algorithm (NewtonRaphson)
It is now possible to compute the static equilibrium of a SIMO
system
by using a NewtonRaphson algorithm. The method used in the previous
SIMO
versions is now referred to as "Transient".
Some remarks when using the NewtonRaphson method:  the NewtonRaphson method is generally faster when considering a system with only one body  the "transient" method still remains the most robust method, especially in case of systems with several bodies, and/or with strong nonlinearities (like fenders, DP systems, …).
It is recommended to use the "transient" method as the default method.
Restraining global degrees of freedom
When using the NewtonRaphson method, the user can choose to restrain the "global" degrees of freedom of one or several bodies during the static equilibrium calculation. By "global" degrees of freedom, we refer here to the translations and rotations about the axes of the XGB coordinate system.
Multiple equilibrium calculations
When using the NewtonRaphson method, it is possible to use the "multiple equilibrium calculation" option on one specified body. This allows the user to define a grid of roll and pitch values. For each point of the grid, the equilibrium position will be computed, restraining the roll and pitch rotations. This means that the equilibrium is solved for the other degrees of freedom.
Note that in the present version, the results are stored in the prs.lis
file but are not available directly in SIMA
. This will be updated in a
future version of SIMO
/SIMA
.
New option in quadratic current force coefficients
It is now possible to model the quadratic current coefficients as a function of:  relative current direction  body vertical position  body roll angle  body pitch angle
New option in wind force coefficients
It is now possible to model the wind coefficients as a function of:  relative wind direction  body vertical position  body roll angle  body pitch angle
New option in hydrostatic stiffness model
It is now possible to model the nonlinear buoyancy force by means of
volume integration, by using the new Hydrostatic Stiffness option
Nonlinear hydrostatic stiffness
. The geometry of the hull is given as
a STL file (mesh of triangular panels) allowing the definition of
complex geometries.
New option in TDM model
It is now possible to model a ballast system made of an unlimited number
of ballast tanks by using the TDM new option BALLAST SYSTEM
. The
geometry of each tank is described by a STL file (mesh of triangular
panels) allowing the definition of complex geometries.
Change in environment during simulation
Functionality is added for changing the wave, wind, and current over the course of a simulation. The program fades from one environment to the next defined environment at the prescribed time over the specified fadein period.
RIFLEX line tension measurements in DP system
A new option has been added that allows the SIMO
DP system to receive
line tension measurements from RIFLEX
lines in a coupled simulation.
Previously this has only been possible for SIMO
catenary lines. See
the the section on Dynamic positioning
in the userguide for more details.
SIMO 4.10.0 Removed functionality
No previously available functionality have been removed in version 4.10.
SIMO 4.10.0 Deprecated functionality
The following functionality is deprecated and will be removed in a
future version of SIMO
:  The simplified line dynamics model for
catenary lines (LINPTY = 3
in LINE CHARACTERISTICS DATA
)  The strip
model for quadratic current coefficients
(QUADRATIC CURRENT COEFFICIENTS
)  The old thruster specification
(THRUST
) and the old DP model (DYNAMIC POSITIONING SYSTEM
)
SIMO 4.8
SIMO 4.8 Input changes
Input files used in version 4.6 can be used unchanged in version 4.8 with the following exceptions:  Input files for models with an external DP system (MTDP) must be updated.
Positioning element force components
Time series of force components for positioning elements are now
available as results in SIMA
.
Corrected in SIMO
4.8.8.
Memory size in S2XMOD
S2XMOD
now uses the SIMO_MEM
environment variable to determine the
amount of memory that is allocated.
Corrected in SIMO
4.8.6.
Sporadic crashes when using visualization waves
An error which caused SIMO to crash sporadically when using visualization waves has been fixed. The error did not influence simulation results in any way.
Corrected in SIMO
4.8.5.
There have been made no changes to SIMO
in this release.
Corrected in SIMO
4.8.4.
Linux binary files
The record length of the binary files was set to four times the correct value. The .ffi, .sam, .raf, .bin and .tda files were therefore four time their necessary size. The .bin and .tda files were not comparable with their documentation and preexisting tools for reading them.
Error since 4.8.0. Corrected in SIMO
4.8.3.
SIMO crash when using articulated structure
A bug has been fixed where SIMO sometimes would crash when using the articulated structure functionality.
Corrected in SIMO
4.8.1.
Unexpected simulation failure when when simulating thruster blackout
In certain cases when using the new thruster model and specifying thruster blackout the simulation would fail unexpectedly. This has now been fixed.
Corrected in SIMO
4.8.0.
SIMO 4.8 New / improved functionality
Improved eigenmode calculations
The underlying linear algebra routine in eigenmode calculations has been replaced. The new routine gives improved accuracy, especially for longer eigenperiods. Note that this means slightly modified results.
MTDP system changes
The MTDP functionality for external DP systems have been changed so that
SIMO
is now the server in the TCP/IP communication. As a result any
external DP systems using the MTDP protocol must be changed from being a
TCP/IP server to a TCP/IP client. The input of MTDP hostname have been
removed from the SIMO
sysfile as it is no longer needed.
Controling thrusters using the new thruster model is now supported through the MTDP interface.
New Linux release
The new Linux release of SIMO
, RIFLEX
and VIVANA
is 64bit and
solves several issues. Unfortunately, this means that 32bit Linux
operating systems are no longer supported.

Supports more than the 32bit imposed limit of 2 GB of RAM

No need to install 32bit support libraries separately

No special considerations are needed for writing output files larger than 2 GB

The necessary runtime libraries are included in the installation package and no special consideration is needed for installation; the package is now fully relocatable
The package has been tested on the following Linux distributions:

CentOS 7

Ubuntu 14.04 LTS

Linux Mint 17
SIMO 4.6
SIMO 4.6 Corrected errors
Coordinate system for stiffness forces
Stiffness forces are now presented in body related coordinate system. In previous SIMO versions they were presented in body fixed system.
Corrected in SIMO
4.6.2.
Error when thruster formulation 4.1
In previous SIMO versions the thruster dynamic was not calculated correctly when using formulation 4.1, which could lead to numerical problems. This error has now been fixed. Simulations using thrusters and DP controller with formulation 4.1 should be rerun.
Corrected in SIMO
4.6.1.
Error when using swell waves with summation of harmonic components (cosine series) in the time domain
In previous SIMO versions, an error prevented time series generation using the summation of harmonic components (cosine series) in the time domain for environments with swell waves. This error has now been fixed.
SIMO 4.6 New / improved functionality
Change in applied reference system for large volume wave loads in case load heading correction is disregarded
The wave forces are now applied in bodyrelated reference system instead of the fixed initial reference system. This ensures that the wave forces and corresponding reaction forces now act in the same system for nonzero yaw angles, which in turn leads to a more numerically robust solution of the system of equations. This correction is expected to give insignificant changes to results for normal analysis with small yaw motions. However, the changes in results will become larger with larger yaw motions.
SIMO 4.4
SIMO 4.4 Corrected errors
Error when using Nonlinear Buoyancy Correction for bodies with wave drift force coefficients
In previous SIMO versions the nonlinear buoyancy correction was not calculated correctly when used for bodies which also had wave drift force coefficients. This error has now been fixed. Simulations using the Nonlinear Buoyancy Correction feature along with wave drift force coefficients should be rerun.
Corrected in SIMO
4.4.2.
SIMO 4.4 New / improved functionality
Time dependent mass
Possible problem with numerical precision when using TIME DEPENDENT MASS. This has been counteracted by increasing the numerical precision during accumulation of the time dependent mass.
Improved bumper formulation
The bumper formulation has been improved when contact occurs at the end of a bumper. The mathematical model can be regarded as if there are halfspheres at the end of all bumper elements. For more details see `Bumpers' in `Stationkeeping forces' in `Force models' in the SIMO Theory Manual.
Improved in SIMO
4.4.1.
SIMO 4.4 Removed functionality
The option for wave force modification under
Nonlinear modification of buoyancy and wave forces
is temporarily
removed.
SIMO 4.2
SIMO 4.2 Input changes
4.0 input files may be used unchanged.
Input for new functionality is described in the User Manual.
SIMO 4.2 Corrected errors
The following errors have been corrected in SIMO
4.2 versions.
Hydrodynamic drag forces on slender elements
If depth dependent current was applied and wind also was specified in the environmental condition, the computed current drag forces on slender elements were in error. This was due to an incorrect zposition being used to interpolate the shear profile. The error has been present since version 4.2.0. The consequence is incorrect drag forces on the slender elements. Analysis done with this combination by version 4.2.0 should be rerun! The error has been corrected.
Corrected in SIMO
4.2.1.
Nonlinear modification of buoyancy and wave forces
The formulation is corrected so that no modification to drift forces is made if no waves are active. Normally of no consequence to results.
Corrected in SIMO
4.2.1.
Error correction: Thruster forces
To be in accordance with the old deprecated thruster force model the thrust forces from the "new thruster" model (THRUSTER SYSTEM DATA) are updated at each main time step and kept constant during substepping. This will give insignificant consequence to the results.
Corrected in SIMO
4.2.1.
SIMO 4.2 Improvements
The following errors have been corrected in SIMO
4.2 versions.
Nonlinear modification of buoyancy and wave forces
The applied models for wave and hydrostatic stiffness loading acting on a "large volume" body are based on a hydrodynamic input description precalculated for a certain draught assuming constant geometry of the intersection between the hull and the mean water level. This means that the body fixed coordinate system has to coincide with the system used for computation of the hydrodynamic potential flow solution and that the load model for nonlinear modification of buoyancy and wave forces has to be initialized at the appropriate draught.
Originally the load model was initialized at the initial position of the body. This created unwanted requirements to the initial position which had to coincide with the origin of the system used for hydrodynamic calculations.
In the improved version the load model is initialized at the reference position for hydrostatic stiffness forces. As a consequence the reference position has to coincide with the origin of the system used for hydrodynamic calculations. This implies that the reference position can not be used to introduce specified force in global Zdirection, nor moments for roll or pitch.
Improved in SIMO
4.2.1.
SIMO 4.2 New functionality
New thruster model (THRUSTER SYSTEM DATA)
The "old" thruster model (THRUSTER DATA
) can still be used in the
current version of SIMO
, but is marked as "deprecated", meaning that
it will be removed in the next release version. The new thruster model
has two main additional features compared to the "old" one:

Dynamics of the thruster has been improved, including a simple servomotor model

An option for thrust loss due to surface proximity is included
Note 1: for a given body, all thrusters have to be modelled with the same model (all with the "old" one or all with the "new" one).
Note 2: the new thruster model cannot be used with the "old" DP model
(DYNAMIC POSITIONING SYSTEM
)
New DP model (DYNAMIC POSITIONING CONTROL)
The "old" DP model (DYNAMIC POSITIONING SYSTEM
) can still be used in
the current version of SIMO
, but cannot be used with the new thruster
model (see section above). It is marked as "deprecated", meaning that
it will be removed in the next release version. The new DP model has one
main additional feature compared to the "old" one: the thruster data
used by the DP system has to be given separately from the physical
thruster data. The DP model does no longer "know" everything about the
physical thruster, and can now be provided with wrong or inaccurate
information if one wants to do error analysis or check robustness.
Further, the DP system does not have to use all thrusters, but only
those assigned to it.
Note: the new DP model can only be used with the "new" thruster model
(THRUSTER SYSTEM DATA
)
Wind forces on slender elements
In data group DISTRIBUTED ELEMENT FORCE
it is now possible to include
wind drag forces on slender elements. Quadratic wind drag coefficients
in x, y and zdirection are then given in data group
AERODYNAMIC DESCRIPTION
.
Nonlinear modification of buoyancy and wave forces
In the new version it is possible to account for nonlinear buoyancy due to the variation in vessel geometry above and below the stillwater plane.
The basic first order wave forces and wavedrift forces are computed as
before using transfer functions and wavedrift coefficients. Then the
nonlinear correction is obtained by integrating pressure forces on the
instantaneously additional wet/dry surface. New input is a file in
socalled (.gdf
) format, containing the hull geometry in the splash
zone.
Winch control using Generic External Control System
A new feature Generic External Control System has been added to enable
SIMO
simulations with user developed control systems. External control
systems are developed using a Java interface defined in HLAlib.jar
.
Currently the system supports controlling SIMO
winches.