1. Winch specification

This data group is optional and is available as additional information for Arbitrary Systems only.

It enables the user to model winch / winching. Boundary conditions previously defined for nodes attached to the winch will be substituted by the winch specification. For normal riser systems this data group should not be considered.

In the following the input parameters are described. Several winches may be specified. The lines in this group must be given in one block for each winch.

1.1. Data group identifier, one input line

WINCh SPECification

1.2. Specification of winch(es), one input line

NWINCH

  • NWINCH: integer: Number of winches

Winch identifier, one input line
IDWINCH

  • IDWINCH: character(8): Winch identifier

Initial location of winch point, one input line
ILIN_W ISEG_WP RLSEG_WP IEND_W

  • ILIN_W: integer: Line number attached to winch

  • ISEG_WP: integer: Local segment number at winch point

  • RSEG_WP: real: Relative segment length where segment is attached to winch point

  • IEND_W: integer: End of segment (and line) attached to winch (1 or 2)

figurwinch

Final position of winch point, one input line
XW YW ZW ROTW DIRW

  • XW: real: Coordinates for static equilibrium position \(\mathrm {[L]}\)

  • YW: real: Coordinates for static equilibrium position \(\mathrm {[L]}\)

  • ZW: real: Coordinates for static equilibrium position \(\mathrm {[L]}\)

  • ROTW: real: Specified rotation of supernode from stress free position to static equilibrium position \(\mathrm {[deg]}\)

  • DIRW: real: Direction of axis for specified rotation \(\mathrm {[deg]}\)

Boundary condition of winch, one input line
CBOUND CIBODY

  • CBOUND: character(6): Boundary condition for winch (All nodes attached to winch)

    • = FIXED: Fixed boundaries

    • = VESSEL: Winch attached to support vessel

    • = FLOATE: Winch attached to floater force model (`SIMO' body)

  • CIBODY

    • = IVES: integer: Support vessel number (CBOUND = VESSEL)

    • = CHBODY: character(8): Floater force model identifier (CBOUND = FLOATE)

    • (Dummy for CBOUND=FIXED)

Winch properties, one input line
VELMAX TIMMAX LDROP RADIUS IZSIGN LELVAR

  • VELMAX: real: Maximum winch velocity \(\mathrm {[L/T]}\)

  • TIMMAX: real: Time to reach maximum velocity (from zero) \(\mathrm {[T]}\)

  • LDROP: integer: Line release when no more line on winch (Dynamic analysis)

    • = 0 Not possible

    • = 1 Possible

  • RADIUS: real > 0: Radius of winch \(\mathrm {[L]}\)

  • IZSIGN: integer: = \(\mathrm {\pm1}\) Center of winch in positive or negative local Z-axis

  • LELVAR: integer: Control parameter for adjusting the length of elements attached to winch.

    • = 0 No justification

    • = 1 Justification

The parameters RADIUS, IZSIGN and LELVAR specify how the elements attached to the winch are visualized.

For LELVAR=0: \(\mathrm {RADIUS>=(EL)/\sqrt{2}}\), where \(\mathrm {EL}\) is length of shortest element attached to the winch.

Final position for winch is dummy for coupled analysis.

The RIFLEX winch formulation is intended for vertical winching and may be unstable when deviating from vertical in dynamic analysis.

It is recommended to apply some numerical damping when using the winch functionality, for example BETIN=3.9 and GAMMA=0.505, see Time Domain Procedure.

The Winch rotations follow the same conventions as prescribed rotations of nodes, see Boundary conditions. The coordinate system is rotated first using DIRW, followed by ROTW.

If Rotation direction DIRW is set to 0.0, the winch will rotate ROTW degrees around the local y-axis. It is important to note that the coordinate system is rotated first relative to the global system using DIRW, the winch is then rotated ROTW degrees around the y-axis in the updated coordinate system.
um ii fig47 winch
Figure 1. Sketch of a winch model