Coupling Specification

1. 1 input line

COUPling DATA

2. 1 input line

CHCPL

CHCPL: character(8): Coupling identifier

3. Text for describing the coupling system, 2 input lines.

TXCPL

TXCPL: character(60): Character string describing the coupling

The data group in the four previous input lines must be followed by a specification of one of the following coupling models. This means that in the case of several or multiple couplings, the previous data group has to be repeated.

4. Simple wire coupling

1 identifying input line

SIMPle WIRE COUPling

Connection point 1 - Alternative 1: 1 input line

CHBDY1   XBDY1   YBDY1   ZBDY1

CHBDY1: character(8): Identifier for body 1
XBDY1: real: X-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).
YBDY1: real: Y-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).
ZBDY1: real: Z-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).

Connection point 1 - Alternative 2: 1 input line

CPL_NAME1

CPL_NAME1: character(32): Name (identifier) of coupling point in end 1

CPL_NAME1 must have been defined as a coupling point in data group "COUPling POINt".

CPL_NAME1 must be identical to identifier CHCOPO.

Connection point 2 - Alternative 1: 1 input line

CHBDY2   XBDY2   YBDY2   ZBDY2

CHBDY2: character(8): Identifier for body 2
XBDY2: real: X-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).
YBDY2: real: Y-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).
ZBDY2: real: Z-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).

Connection point 2 - Alternative 2: 1 input line

CPL_NAME2

CPL_NAME2: character(32): Name (identifier) of coupling point in end 2

CPL_NAME2 must have been defined as a coupling point in data group "COUPling POINt".

CPL_NAME2 must be identical to identifier CHCOPO. CPL_NAME2 must be different from CPL_NAME1.

1 input line if guide points are wanted ( NGUIDE > 0 )

NGUIDE

NGUIDE: integer: Number of guide points
- = 0 if no guide points are specified

NGUIDE input lines

CHGUPO  IACTIVE

CHGUPO: character(32): Identifier for guide point
IACTIVE: integer, default: 1:
- = 0: Guide point not entered on line
- = 1: Coupling point entered on line

1 input line

EA   RLEN   FLEXC   DAMPSW    IREST   EHLA   HLACON1   HLACON2   ICT

EA: real: Wire cross section stiffness, \(\mathrm {[F]}\)
RLEN: real: Initial, unstretched wire length, \(\mathrm {[L]}\)
FLEXC: real, default: 0: Connection flexibility, \(\mathrm {[L/F]}\)
DAMPSW: real, default: 0: Material damping \(\mathrm {[FT]}\). \(\mathrm {Force=dampsw*(\Delta L/\Delta t)/L}\)
IREST: integer, default: 0: Flag for "Restoring Coupling", only used in STAMOD
EHLA: integer, default: 0: HLA export flag for simplified wire,
- = 0: No export
- = 1: HLA Export
HLACON1: integer, default: 0: HLA control flag for connection of line end 1
- = 0: not HLA connectable
- = 1: HLA connectable
HLACON2: integer, default: 0: HLA control flag for connection of line end 2,
- = 0: not HLA connectable
- = 1: HLA connectable
ICT: integer, default: 0: Constant tension control
- = 0: Disabled
- = 1: Enabled

FLEXC (inverse of stiffness) is the flexibility in the wire attachment point. This flexibility should account both for flexibility in the construction and elasticity in the wire between the winch and the used wire attachment point.

DAMPSW is specified material damping in the line. The value can normally be set to 1-2% of E * A, where E is the modulus of elasticity and A is the cross-sectional area.

If EHLA = 1, 1 input line, HLA name of simple wire object,

CHCHLA

CHCHLA: character(120): Character string describing HLA coupling object name

If HLACON1 = 1, 1 input line, HLA name of connectable line end 1

CHCON1

CHCON1: character(120): Character string describing HLA connectable line end 1

If HLACON2 = 1, 1 input line, HLA name of connectable line end 2

CHCON2

CHCON2: character(120): Character string describing HLA connectable line end 2

If ICT = 1, 1 input line

Wire length will be adjusted trying to keep tension within \(\mathrm {TSET-DEADB/2}\) and \(\mathrm {TSET+DEADB/2}\). The change in wire length is constrained by VMAX.

TSET DEADB VMAX

TSET: real: Tension set point \(\mathrm {[F]}\)
DEADB: real: Tension control deadband \(\mathrm {[F]}\)
VMAX: real: Maximum run speed of winch controlling tension \(\mathrm {[L/T]}\)
TACT: real, default=0: Activation time of controller \(\mathrm {[T]}\)
TDEACT: real, default=0: Deactivation time of controller\(\mathrm {[T]}\)

The wire length will not be adjusted until simulation time is larger than or equal to the given activation time, TACT. If the controller deactivation time, TDEACT, is less than or equal to the activation time the controller will always remain active.

Element failure, 1 input line

IFMOCO FTIME BTENS

IFMOCO: integer: Failure mode of coupling element
- = 0: no failure
- = 1: failure by exceedance of BTENS after specified time
  - The coupling element breaks when both FTIME and BTENS are exceeded
- = 2: failure activated after specified time if Tens < BTENS
FTIME: real: Earliest possible time of failure, \(\mathrm {[T]}\)
BTENS: real: Breaking strength, \(\mathrm {[F]}\)

5. Multiple wire coupling

Multiple wire couplings makes it possible to model several wire segments connected in a common branch point, for example a crane wire with a sling arrangement, connected in the hook.

Each of the wire segments must be separately specified by COUPling DATA and MULTiple WIRE COUPling data groups, e.g. each segment is treated as a separate coupling. Typically 2-4 segments are attached to one body (lifted object), and 1 segment to another body (crane vessel).

1 identifying input line

MULTiple WIRE COUPling

Connection points - Alternative 1: 1 input line

CHBRAN   CHBDY   XBDY   YBDY   ZBDY

CHBRAN: character(8): Identifier for branch point.
CHBDY: character(8): Identifier for body.
XBDY: real: X-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).
YBDY: real: Y-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).
ZBDY: real: Z-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).

Connection points - Alternative 2: 1 input line

CHBRAN   CPL_NAME2

CHBRAN: character(8): Identifier for branch point.
CPL_NAME2: character(32): Name (identifier) of coupling point in end 2

1 input line

EA   RLEN   FLEXC   DAMPSW    IREST   EHLA

EA: real: Wire cross section stiffness, \(\mathrm {[F]}\).
RLEN: real: Initial, unstretched wire length, \(\mathrm {[L]}\).
FLEXC: real, default: 0: Connection flexibility, \(\mathrm {[L/F]}\).
DAMPSW: real, default: 0: Material damping \(\mathrm {[FT]}\). \(\mathrm {Force=dampsw*(\Delta L/\Delta t)/L}\)
IREST: integer, default: 0: Flag for "Restoring Coupling", only used in STAMOD
EHLA: integer, default: 0: HLA export flag for multiple wire element
- = 0: No export
- = 1: HLA export

DAMPSW is specified material damping in the line. The value can normally be set to 1-2% of E*A, where E is the modulus of elasticity and A is the cross-sectional area.

If EHLA = 1, 1 input line, HLA name of multiple wire object,

CHCHLA

CHCHLA: character(120): Character string describing HLA coupling object name

Element failure, 1 input line

IFMOCO FTIME BTENS

IFMOCO: integer: Failure mode of coupling element
- = 0: no failure
- = 1: failure by exceedance of BTENS after specified time
FTIME: real: Earliest possible time of failure, \(\mathrm {[T]}\).
BTENS: real: Breaking strength, \(\mathrm {[F]}\).

The coupling element breaks when both FTIME and BTENS are exceeded

6. Lift line coupling

The lift line coupling is a single line model, which includes in a simplified way the following features:

drag forces on the line
static line weight
longitudinal inertia forces due to vertical acceleration at both ends.

The model assumes that the line is straight.

1 identifying input line

LIFT LINE COUPling

Connection point end 1 - Alternative 1: 1 input line

CHBDY1   XBDY1   YBDY1   ZBDY1

CHBDY1: character(8): Identifier for body 1
XBDY1: real: X-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).
YBDY1: real: Y-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).
ZBDY1: real: Z-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).

Connection point end 1 - Alternative 2: 1 input line

CPL_NAME1

CPL_NAME1: character(32): Name (identifier) of coupling point in end 1

CPL_NAME1 must have been defined as a coupling point in data group "COUPling POINt".

CPL_NAME1 must be identical to identifier CHCOPO

Connection point end 2 - Alternative 1: 1 input line

CHBDY2   XBDY2   YBDY2   ZBDY2

CHBDY2: character(8): Identifier for body 2
XBDY2: real: X-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).
YBDY2: real: Y-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).
ZBDY2: real: Z-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).

Connection point end 2 - Alternative 2: 1 input line

CPL_NAME2

CPL_NAME2: character(32): Name (identifier) of coupling point in end 2

CPL_NAME2 must have been defined as a coupling point in data group "COUPling POINt".

CPL_NAME2 must be identical to identifier CHCOPO. CPL_NAME2 must be different from CPL_NAME1.

1 input line

NEL  IACC  EHLA  HLACON1  HLACON2

NEL: integer: Number of elements in the line
IACC: integer, default: 0: Flag for including acceleration of the line
- = 0: No acceleration of the line included
- = 1: Acceleration of the line included in the force calculations
EHLA: integer, default: 0: HLA export flag for lift line,
- = 0: No export
- = 1: HLA Export
HLACON1: integer, default: 0: HLA control flag for connection of line end 1
- = 0: not HLA connectable
- = 1: HLA connectable
HLACON2: integer, default: 0: HLA control flag for connection of line end 2
- = 0: not HLA connectable
- = 1: HLA connectable

The model for including line acceleration in the line force calculations is simplified, assuming linear variation of acceleration along the length.

If EHLA = 1, 1 input line, HLA name of lift line object

CHCHLA

CHCHLA: character(120): Character string describing HLA coupling object name

If HLACON1 = 1, 1 input line, HLA name of connectable line end 1

CHCON1

CHCON1: character(120): Character string describing HLA connectable line end 1

If HLACON2 = 1, 1 input line, HLA name of connectable line end 2

CHCON2

CHCON2: character(120): Character string describing HLA connectable line end 2

1 input line

 DIA   EMOD   EMFACT   RLEN   FLEXC   DAMPSW

DIA: real: Segment diameter, \(\mathrm {[L]}\)
EMOD: real: Modulus of elasticity \(\mathrm {[F/L^2]}\)
EMFAC: real: Factor of elasticity
- = 2: For chains
- = 1: For other segment types
RLEN: real: Initial, unstretched line length, \(\mathrm {[L]}\)
FLEXC: real, default: 0: Connection flexibility, \(\mathrm {[L/F]}\)
DAMPSW: real, default: 0: Material damping \(\mathrm {[FT]}\). \(\mathrm {Force=DAMPSW*(\Delta L/\Delta t)/L}\)

Total stiffness, \(\mathrm {EA=EMOD\times EMFAC\times DIA^2\times \pi /4}\)

DAMPSW is material damping in the line. The value can normally be set to 1-2% of E*A, where E is the modulus of elasticity and A is the cross-sectional area.

1 input line

UWIA   WATFAC   CDN   CDL

UWIA: real: Unit weight in air, \(\mathrm {[F/L]}\)
WATFAC: real: The ratio of weight in water to weight in air.
- Normally 0.81 for wire and 0.87 for chain
CDN: real: Transverse drag coefficient of the line
CDL: real: Longitudinal drag coefficient of the line .
Drag force/length = 0.5 * RHOW * DIA * CDN * VN\(\mathrm {^2\quad }\) Transverse
Drag force/length = 0.5 * RHOW * DIA * CDL * VL\(\mathrm {^2\quad }\) Longitudinal

Element failure, 1 input line

IFMOCO FTIME BTENS

IFMOCO: integer: Failure mode of coupling element
- = 0: no failure
- = 1: failure by exceedance of BTENS after specified time
  - The coupling element breaks when both FTIME and BTENS are exceeded
- = 2: failure activated after specified time if Tens < BTENS
FTIME: real: Earliest possible time of failure, \(\mathrm {[T]}\)
BTENS: real: Breaking strength, \(\mathrm {[F]}\)

Note! The coupling element breaks when both FTIME and BTENS are exceeded.

7. Force-elongation with fixed attack points

1 identifying input line

FIXEd ELONgation COUPling

Connection point 1 - Alternative 1: 1 input line

CHBDY1   XBDY1   YBDY1   ZBDY1

CHBDY1: character(8): Identifier for body 1
XBDY1: real: X-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).
YBDY1: real: Y-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).
ZBDY1: real: Z-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).

Connection point 1 - Alternative 2: 1 input line

CPL_NAME1

CPL_NAME1: character(32): Name (identifier) of coupling point in end 1

CPL_NAME1 must have been defined as a coupling point in data group "COUPling POINt".

CPL_NAME1 must be identical to identifier CHCOPO.

Connection point 2 - Alternative 1: 1 input line

CHBDY2   XBDY2   YBDY2   ZBDY2

CHBDY2: character(8): Identifier for body 2
XBDY2: real: X-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).
YBDY2: real: Y-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).
ZBDY2: real: Z-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).

Connection point 2 - Alternative 2: 1 input line

CPL_NAME2

CPL_NAME2: character(32): Name (identifier) of coupling point in end 2

CPL_NAME2 must have been defined as a coupling point in data group "COUPling POINt".

CPL_NAME2 must be identical to identifier CHCOPO. CPL_NAME2 must be different from CPL_NAME1.

1 input line

NPT  IMETH  EXP  INTPOC  VEMIC  EHLA

NPT: integer: Number of points in characteristics
IMETH: integer: Method for initialisation of coupling element
- = 3: Spring, coordinates of both end points are given
- = 5: Constant tension winch, coordinates of both end points are given. Maximum and minimum tension specified in the characteristic will not be exceeded.
EXP: real, default: 1: Exponent of velocity in damping term
INTPOC: integer, default: 1: Interpolation method = 1, 2, 3 or 4
- =1: Linear force, linear damping.
- =2: Linear force, parabolic damping.
- =3: Parabolic force, linear damping.
- =4: Parabolic force, parabolic damping.
VEMIC: real, default: 0: Velocity limit for friction force (EXP = 0) See below.
EHLA: integer, default: 0: HLA export flag for coupling element
- = 0: No export
- = 1: HLA export

Small velocities and EXP=0. will result in problems in finding equilibrium position because the friction force (which may be relatively large) suddenly can change sign. To avoid this the value EXPD=1 is used when Abs(vel.)<VEMIN and EXPD<1.

The damping force (EXP=1) for Vel`=VEMIC` is equal to Damping force (`EXP=`as given).

If EHLA = 1, 1 input line, HLA name of force-elongation object,

CHCHLA

CHCHLA: character(120): Character string describing HLA coupling object name

NPT input lines.

DIST FORCE DAMP

DIST: real: Distance between end points, \(\mathrm {[L]}\).
FORCE: real: Force in element, positive values signify attraction of the bodies, \(\mathrm {[F]}\).
DAMP: real: Damping coefficient, \([F(T/L)^{\mathrm {EXP}}]\).

Distances are to specified in increasing order and can not be negative.

Element failure, 1 input line (Shall be given for all values of IMETH)

IFMOCO FTIME BTENS

IFMOCO: integer: Failure mode of coupling element
- = 0: No failure
- = 1: Failure by exceeding the tension after specified time.
- = 2: Activated after specified time if Tens < BTENS
FTIME: real: Earliest possible time of failure, \(\mathrm {[T]}\).
BTENS: real: Breaking strength, \(\mathrm {[F]}\).

Note! The coupling element breaks when both FTIME and BTENS are exceeded

8. Docking cone coupling

1 identifying input line

DOCKing CONE COUPling

Connection point 1 - Alternative 1: 1 input line

CHBDY1   XBDY1   YBDY1   ZBDY1

CHBDY1: character(8): Identifier for body 1
XBDY1: real: X-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).
YBDY1: real: Y-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).
ZBDY1: real: Z-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).

Connection point 1 - Alternative 2: 1 input line

CPL_NAME1

CPL_NAME1: character(32): Name (identifier) of coupling point in end 1

CPL_NAME1 must have been defined as a coupling point in data group "COUPling POINt".

CPL_NAME1 must be identical to identifier CHCOPO.

Connection point 2 - Alternative 1: 1 input line

CHBDY2   XBDY2   YBDY2   ZBDY2

CHBDY2: character(8): Identifier for body 2 (Body with cone)
XBDY2: real: X-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).
YBDY2: real: Y-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).
ZBDY2: real: Z-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).

Connection point 2 - Alternative 2: 1 input line

CPL_NAME2

CPL_NAME2: character(32): Name (identifier) of coupling point in end 2

CPL_NAME2 must have been defined as a coupling point in data group "COUPling POINt".

CPL_NAME2 must be identical to identifier CHCOPO. CPL_NAME2 must be different from CPL_NAME1

1 input line

NPT  EXP  INTPOC  VEMIC  EHLA

NPT: integer: Number of points in characteristics
EXP: real, default: 1: Exponent of velocity in damping term,
INTPOC: integer, default: 1: Interpolation method = 1, 2, 3 or 4
- =1: Linear force, linear damping.
- =2: Linear force, parabolic damping.
- =3: Parabolic force, linear damping.
- =4: Parabolic force, parabolic damping.
VEMIC: real, default: 0: Velocity limit for friction force (EXP = 0). See below.
EHLA: integer, default: 0: HLA export flag for coupling element
- = 0: No export
- = 1: HLA export

Small velocities and EXP=0 will result in problems in finding equilibrium position because the friction force (which may be relatively large) suddenly can change sign. To avoid this the value EXPD=1 is used when Abs(vel.)<VEMIN and EXPD<1.

The damping force (EXP=1) for Vel`=VEMIC` is equal to Damping force (`EXP=`as given).

For EHLA = 1, 1 input line

CHCHLA

CHCHLA: character(120): Character string describing HLA coupling object name

1 input line

NAXPTS

NAXPTS: integer: Number of axial points with given force characteristics

1 input line

RADMAX   FRIC

RADMAX: real: Maximum radial distance at entry
FRIC: real: Friction coefficient for sliding along the cone or cylinder surface

1 input line

DV1 DV2 DV3

DV1: real, default: 0: Direction vector, x-component
DV2: real, default: 0: Direction vector, y-component
DV3: real, default: -1: Direction vector, z-component

Direction vectors of guide axis are defined in local coordinate system of body 2 (direction from end of cylinder and inwards). They will be normalised in the input module.

NAXPTS input lines.

IAXPT AXPT

IAXPT: integer: Axial point number
AXPT: real: Axial point, axial distance from end, \(\mathrm {[L]}\)

NAXPT * NPT input lines.

DIST FORCE DAMP

DIST: real: Radial distance (transverse offset), \(\mathrm {[L]}\)
FORCE: real: Force in element, positive values signify attraction of the bodies, \(\mathrm {[F]}\)
DAMP: real: Damping coefficient, \([F[T/L]^{\mathrm {EXP}}]\)

Distances should be increasing and can not be negative, and each characteristic must have the same number of distances.

Force characteristics for each axial point, starting with point 1. At least one force-value must be zero.

Element failure, 1 input line

IFMOCO FTIME BTENS

IFMOCO: integer: Failure mode of coupling element
- = 0: No failure
- = 1: Failure by exceeding the tension after specified time.
- = 2: Activated after specified time if Tens < BTENS
FTIME: real: Earliest possible time of failure, \(\mathrm {[T]}\)
BTENS: real: Breaking strength, \(\mathrm {[F]}\)

Note! The coupling element breaks when both FTIME and BTENS are exceeded

9. Fender coupling

1 identifying line

FENDer COUPling

1 input line

NPT   IFRIC   DYNFRIC   STAFRIC   STIFFRIC    EXP   INTPO   VEMIN  EHLA

NPT: integer: Number of points in characteristics
IFRIC: integer: Fender model
- = 1: Fender point
- = 2: Fender roller (zero friction in one direction)
DYNFRIC: real: Dynamic friction coefficient, sliding
STAFRIC: real: Friction coefficient, when not sliding (stiction)
STIFFRIC: real: Shear stiffness associated with friction \(\mathrm {[F/L]}\)
EXP: real: Exponent of velocity in damping term
INTPO: integer: Interpolation method = 1,2,3 or 4
- =1: Linear force, linear damping.
- =2: Linear force, parabolic damping.
- =3: Parabolic force, linear damping.
- =4: Parabolic force, parabolic damping.
VEMIN: real, default: 0: Velocity limit for normal friction force (EXP=0)
EHLA: integer, default: 0: HLA export flag for fender
- = 0: No export
- = 1: HLA export

A fender roller is modeled as a point with zero friction in one specified direction. A spherical fender is a sphere with given diameter and omni-directional friction.

Small velocities and EXP=0 can result in a large normal friction force that suddenly changes sign. To avoid this the value EXP=1 will be used when Abs(vel.)<VEMIN and EXP<1.

If EHLA = 1, 1 input line,HLA name of fender object,

CHCHLA

CHCHLA: character(120): Character string describing HLA coupling object name

Figure 1. Example of friction force (here with constant normal force, AFORCE)

Attachment point on body 1 in local body 1 coordinates (fender point), 1 input line.

CHBDY1    XF   YF   ZF

CHBDY1: character(8): Identificator of body 1
XF: real: X-coordinate of fender point, \(\mathrm {[L]}\)
YF: real: Y-coordinate of fender point, \(\mathrm {[L]}\)
ZF: real: Z-coordinate of fender point, \(\mathrm {[L]}\)

Definition of fender plane and roller axis in Local body 2 coordinates, 1 input line.

CHBDY2   XP  YP   ZP   XN   YN   ZN   XA   YA   ZA

CHBDY2: character(8): Identificator of body 2
XP: real: X-coordinate of point in the fender plane \(\mathrm {[L]}\)
YP: real: Y- coordinate of point in the fender plane \(\mathrm {[L]}\)
ZP: real: Z- coordinate of point in the fender plane \(\mathrm {[L]}\)
XN: real: X-comp. of vector normal to surface \(\mathrm {[L]}\)
YN: real: Y-comp. of vector normal to surface \(\mathrm {[L]}\)
ZN: real: Z-comp. of vector normal to surface \(\mathrm {[L]}\)
XA: real: X-comp. of vector parallel to fender rotation axis \(\mathrm {[L]}\)
- Dummy for IFRIC = 1
YA: real: Y-comp. of vector parallel to fender rotation axis \(\mathrm {[L]}\)
- Dummy for IFRIC = 1
ZA: real: Z-comp. of vector parallel to fender rotation axis \(\mathrm {[L]}\)
- Dummy for IFRIC = 1

For definition of fender plane dimensions, see the figure `Illustration of fender plane dimensions' below.

May be omitted in case of an unlimited fender plane is modeled, 1 input line

DV1X   DV1Y   DV1Z    RL1     RL2

Vector defining direction no. 1 of fender plane,

DV1X: real: X-component of vector defining direction no. 1
DV1Y: real: Y-component of vector defining direction no. 1
DV1Z: real: Z-component of vector defining direction no. 1
RL1: real: Dimension of fender plane in direction 1
RL2: real: Dimension of fender plane in direction 2

Local body 2 coordinates are used. It is assumed that {XP,YP,ZP} is the centre point of the plane.

NPT input lines

DIST   AFORCE   DAMP

DIST: real: Distance from fender point to fender plane \(\mathrm {[L]}\)
AFORCE: real: Axial fender force, normal to surface \(\mathrm {[F]}\)
DAMP: real: Damping coefficient \([F[T/L]^{\mathrm {EXP}}]\)

The characteristics can be given for monotonic increasing or decreasing distances, DIST

Point fender: All DIST ≤ 0
Spherical fender: All DIST > 0
AFORCE = 0 at the largest distance

Compression force and damping are given as positive numbers

Figure 2. Illustration of fender models

Figure 3. Illustration of fender plane dimensions

10. Bumper element coupling

1 identifying line

BUMPer ELEMent COUPling

1 input line

NPT  INTPOM  VEMIN  EXPD  EHLA

NPT: integer: Number of points in bumper force characteristics
INTPOM: integer, default: 1: Interpolation method = 1,2,3 or 4
- =1: Linear force, linear damping.
- =2: Linear force, parabolic damping.
- =3: Parabolic force, linear damping.
- =4: Parabolic force, parabolic damping.
VEMIN: real, default: 0: Velocity limit for damping force (EXPD=0)
EXPD: real: Exponent in damping
EHLA: integer, default: 0: HLA export flag for bumper
- = 0: No export
- = 1: HLA export

Small velocities and EXPD=0 can result in a large damping force that suddenly changes sign. To avoid this, the value EXPD=1 when Abs(vel.)<VEMIN and EXPD<1.

Figure 4. Example of a pair of bumpers

If EHLA = 1, 1 input line, HLA name of bumper object

CHCHLA

CHCHLA: character(120): Character string describing HLA coupling object name

Coordinates of bumper line attached to body no. 1, 1 input line.

CHBDY1   XA1   YA1   ZA1   XA2   YA2   ZA2

CHBDY1: character(8): Identificator of body 1
XA1: real: X-coordinate of bumper end 1, \(\mathrm {[L]}\)
YA1: real: Y-coordinate of bumper end 1, \(\mathrm {[L]}\)
ZA1: real: Z-coordinate of bumper end 1, \(\mathrm {[L]}\)
XA2: real: X-coordinate of bumper end 2, \(\mathrm {[L]}\)
YA2: real: Y-coordinate of bumper end 2, \(\mathrm {[L]}\)
ZA2: real: Z-coordinate of bumper end 2, \(\mathrm {[L]}\)

Local body 1 coordinates

Coordinates of bumper line attached to body no. 2, 1 input line.

CHBDY2   XB1   YB1   ZB1  XB2   YB2   ZB2

CHBDY2: character(8): Identificator of body 2
XB1: real: X-coordinate of bumper end 1, \(\mathrm {[L]}\)
YB1: real: Y-coordinate of bumper end 1, \(\mathrm {[L]}\)
ZB1: real: Z-coordinate of bumper end 1, \(\mathrm {[L]}\)
XB2: real: X-coordinate of bumper end 2, \(\mathrm {[L]}\)
YB2: real: Y-coordinate of bumper end 2, \(\mathrm {[L]}\)
ZB2: real: Z-coordinate of bumper end 2, \(\mathrm {[L]}\)

Local body 2 coordinates

Contact force characteristics, NPT input lines

DIST   AFORCE   DAMP

DIST: real: Distance between bumper centrelines \(\mathrm {[L]}\)
AFORCE: real: Bumper force, normal to elements \(\mathrm {[F]}\)
DAMP: real: Damping coefficient\([F(T/L)^{\mathrm {EXP}}]\)

The characteristics can be given for increasing or decreasing distances, DIST.

Compression force and damping are given as positive numbers.

11. Ratchet coupling

A ratchet coupling can either give compression or tension force, calculated from stiffness, damping and deviation from a reference length. A compression element will slide (and increase the reference length) when the compressive force becomes smaller than a specified minimum value. Similarly a tension element will slide and decrease the reference length if the tension passes the specified minimum tension.

1 identifying line

RATChet   COUPling

1 input line

CHBDY1   XBDY1   YBDY1   ZBDY1

CHBDY1: character(8): Identifier for body 1
XBDY1: real: X-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).
YBDY1: real: Y-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).
ZBDY1: real: Z-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).

1 input line

CHBDY2   XBDY2   YBDY2   ZBDY2

CHBDY2: character(8): Identifier for body 2
XBDY2: real: X-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).
YBDY2: real: Y-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).
ZBDY2: real: Z-coordinate of coupling connection point in body fixed coordinate system, \(\mathrm {[L]}\).

1 input line

CHTYPE    RFMIN   RSTIFF   TSTART   RDAMP    REXP    VEMIN

CHTYPE: character(4):
- TENSion: Tension element
- COMPression: Pressure element
RFMIN: real: Static force in element \(\mathrm {[F]}\)
RSTIFF: real: Element stiffness \(\mathrm {[F/L]}\)
TSTART: real: Time when dynamics in element will be activated \(\mathrm {[T]}\)
RDAMP: real: Damping coefficient
REXP: real: Exponent in damping
VEMIN: real, default: 0: Velocity limit for damping force (EXPD=0)

RFMIN is minimum compression force if CHTYPE = COMP

RFMIN is minimum tension if CHTYPE = TENS, RFMIN can be zero.

Small velocities and REXP=0 can result in a large damping force that suddenly changes sign. To avoid this, SIMO will use REXP=1 when Abs(vel.)<VEMIN and REXP<1

Element failure, 1 input line

IFAIL  FTIME  F_FAIL

IFAIL: integer: Failure mode of coupling element
- = 0: no failure
- = 1: failure by exceedance of force after specified time
FTIME: real: Earliest possible time of failure, \(\mathrm {[T]}\)
F_FAIL: real: Maximum force, \(\mathrm {[F]}\)

The coupling element fails when both FTIME and F_FAIL are exceeded

12. Moment coupling

1 identification input line.

MOMEnt COUPling

Direction of moment coupling, 1 input line

CHBDY1  DV1  DV2  DV3

CHBDY1: character(8): Identifier for body 1
DV1: real: X-component of rotation axis, \(\mathrm {[L]}\)
DV2: real: Y-component of rotation axis, \(\mathrm {[L]}\)
DV3: real: Z-component of rotation axis, \(\mathrm {[L]}\)

The vector defines the direction of a moment in the body fixed coordinate system of BODY1

This direction will be constant in the local system during a simulation. At each time step the corresponding vector in the global system and in BODY2 system will be calculated. At the initial position, the relative rotation (about the moment axis) is defined to be zero. From one time instant to the next during a simulation, the change in relative rotation about the axis will be computed and added to total relative rotation. This means that the calculated moment related to stiffness will be able to handle rotations of more than 360 degrees (or less than -360deg.)

1 input line

CHBDY2

CHBDY2: real: Identifier for body 2

1 input line

MOM0  MOMK  CPOS  EXPOS  CNEG  EXNEG

MOM0: real: Initial moment \(\mathrm {[FL]}\)
MOMK: real: Moment stiffness \([FL/\mathrm {rad}]\)
CPOS: real: Damping coefficient for positive rotation \([FL(s/\mathrm{rad})^{\mathrm{EXPOS}}\)]
EXPOS: real: Exponent in damping - positive rotation
CNEG: real: Damping coefficient for negative rotation \([FL(s/\mathrm{rad})^{\mathrm{EXNEG}}\)]
EXNEG: real: Exponent in damping - negative rotation

Figure 5. Example of moment coupling

13. External coupling function data

The characteristics of a coupling element can be programmed as an external library, which is executed during a simulation. The required amount of input parameters depends on the external software. All parameters must be written, even if some are dummy (not used).

1 identifying line

EXTErnal COUPling FUNCtion

1 input line, path and filename of library containing the coupling

TXXCO

TXXCO: character(120): Character string giving path and filename

1 input line

NPCUR

NPCUR: integer > 0: Number of points where current velocities shall be given to the external coupling library

1 input lines

CHBDY1 XBDY1 YBDY1 ZBDY1 EHLA

CHBDY1: character(8): Identificator for body 1
XBDY1: real: X-coordinate of body attack point in its body fixed coordinate system, \(\mathrm {[L]}\)
YBDY1: real: Y-coordinate of body attack point in its body fixed coordinate system, \(\mathrm {[L]}\)
ZBDY1: real: Z-coordinate of body attack point in its body fixed coordinate system, \(\mathrm {[L]}\)

1 input line

CHBDY2 XBDY2 YBDY2 ZBDY2

CHBDY2: character(8): Identificator for body 2
XBDY2: real: X-coordinate of body 2 attack point in its body fixed coordinate system, \(\mathrm {[L]}\)
YBDY2: real: Y-coordinate of body 2 attack point in its body fixed coordinate system, \(\mathrm {[L]}\)
ZBDY2: real: Z-coordinate of body 2 attack point in its body fixed coordinate system, \(\mathrm {[L]}\)

1 input line, may be dummy input if not used

NEL   IACC   EHLA

NEL: integer, default: 10: Number of elements in the line
IACC: integer, default: 0: Flag for including acceleration of the line
- = 0: No acceleration of the line
- = 1: Acceleration of the line included in the force calculations
EHLA: integer, default: 0: HLA export flag for coupling
- = 0: No export
- = 1: HLA export

The model for including line acceleration in the line force calculations is simplified.

If EHLA = 1, 1 input line, HLA name of external coupling object,

CHCHLA

CHCHLA: character(120): Character string describing HLA coupling object name

1 input line, may be dummy input if not used

DIA   EMOD   EMFACT   RLEN   FLEXC   DAMPSW

DIA: real: Segment diameter, \(\mathrm {[L]}\)
EMOD: real: Modulus of elasticity \(\mathrm {[F/L^2]}\)
EMFAC: real: Factor of elasticity
- = 2: For chains
- = 1: For other segment types
RLEN: real: Initial, unstretched line length, \(\mathrm {[L]}\)
FLEXC: real, default: 0: Connection flexibility, \(\mathrm {[L/F]}\)
DAMPSW: real, default: 0: Material damping \(\mathrm {[FT]}\). \(\mathrm {Force=dampsw*(\Delta L/\Delta t)/L}\)

Total stiffness, EA = EMOD * EMFAC * DIA\(\mathrm {^2}\) * \(\mathrm {\pi }\)/4.

1 input line, may be dummy input if not used

UWIA   WATFAC   CDN   CDL

UWIA: real: Unit weight in air, \(\mathrm {[F/L]}\)
WATFAC: real: The ratio of weight in water to weight in air, normally 0.81 for wire and 0.87 for chain
CDN: real: Transverse drag coefficient of the line
CDL: real: Longitudinal drag coefficient of the line .
Drag force/length = 0.5 * RHOW * DIA * CDN * VN\(\mathrm {^2\quad }\) Transverse
Drag force/length = 0.5 * RHOW * DIA * CDL * VL\(\mathrm {^2\quad }\) Longitudinal

Element failure, 1 input line

IFMOCO FTIME BTENS

IFMOCO: integer: Failure mode of coupling element
- = 0: no failure
- = 1: failure by exceedance of tension after specified time
- = 2: Activated after specified time if Tens < BTENS
FTIME: real: Earliest possible time of failure, \(\mathrm {[T]}\)
BTENS: real: Breaking strength, \(\mathrm {[F]}\)

The coupling element breaks when both FTIME and BTENS are exceeded