1. Standard system SA

One-point seafloor contact to (surface) vessel. The frequently used steep wave, steep S and jumper configurations are special cases of the SA system. The initial configuration of this system is two-dimensional in X-Z plane.

1.1. Topology

The only variable topology feature is the option of including vertical buoyancy or weight elements in the form of branches.

um ii fig17
Figure 1. Topology of system SA

Introduction of branching points implies that more than one line has to be specified, see the figure Topology of system SA above. Branches are assumed to be vertical in a still water condition. Seafloor and surface contacts are not modelled for this system.

1.2. Data group identifier

SINGle RISEr SA

1.3. Topology

NSNOD

  • NSNOD: integer: Number of supernodes

This implies that number of lines to be defined is NLIN=NSNOD-1, see the figure `Topology of system SA' above.

1.4. Line, line type and supernode connectivity

This data group defines the connectivity between lines and supernodes. If the line identifier is missing the line number implicitly defined by the order in which the lines are specified, will be used as the line identifier. References to line type IDs and supernode numbers are mandatory.

The lines must be specified in the order indicated in the figure Topology of system SA above. This means that the lines are given continuously from seafloor to upper riser end.

At each branching point the line defining a branch is specified before the next line in the main riser configuration. No ball joint components are accepted in branch lines.

NLIN input lines.

LINE-ID LINTYP-ID ISNOD1 ISNOD2

  • LINE-ID: character(8): Line identifier

  • LINTYP-ID: character(8): Reference to line type identifier

  • ISNOD1: integer: Reference to supernode number at end 1

  • ISNOD2: integer: Reference to supernode number at end 2

If only 1 alphanumeric string and 2 integers are specified, the first string is taken as LINTYP-ID.

LINTYP-ID ISNOD1 ISNOD2

The LINE-ID is taken as the line number as implicitly defined by the order in which the lines are given.

1.5. Boundary conditions, coordinates

ZL XU ZU ALFL ALFU

  • ZL: real: Z coordinate of lower end \(\mathrm {[L]}\)

    • X and y coordinates of lower end are set equal to zero.

  • XU: real > 0: X coordinate of upper end \(\mathrm {[L]}\).

  • ZU: real: Z coordinate of upper end \(\mathrm {[L]}\).

    • Y coordinate of upper end is equal to zero

    • Z coordinate is positive upwards

    • ZU=0.0 at still water level (see the figure `Topology of system SA' above).

  • ALFL: real, default: 0.0: Angle of lower end from vertical \(\mathrm {[deg]}\).

  • ALFU: real, default: 0.0: Angle of upper end from vertical \(\mathrm {[deg]}\).

If the lower/upper end later in the specification is allowed to rotate freely around the y-direction, ALFL/ALFU will be dummy.

1.6. Supernode types

NSNOD-2 input lines. ISNOD must be given in increasing order from 2 to NSNOD-2. Only to be given if NSNOD>2.

 ISNOD ITYPSN

  • ISNOD: integer: Supernode ISNOD=2,3, …​. , NSNOD-1

  • ITYPSN: character(6): Type of supernode

    • TSNBRA - Branch point

    • TSNFRE - Free end

Specification of supernodes: Supernode at lower and upper end are not to be specified. Supernode number at lower end is automatically set to 1 and the supernode type is fixed (ITYPSN=TSNFIX). Supernode at upper end is automatically set to NSNOD and the supernode type is specified position (ITYPSN=TSNPOS) indicating that the upper end is connected to the support vessel.

1.7. Support vessel reference

IVES IDWFTR XG YG ZG DIRX

  • IVES: integer, default: 1: Vessel number (IVES = 1)

  • IDWTFR: character (6), default: NONE: Identifier for WF motion transfer function

    • IDWFTR = 'NONE' means no transfer function specified.

  • XG: real:X position of vessel coordinate system referred in global system \(\mathrm {[L]}\)

  • YG: real:Y position of vessel coordinate system referred in global system \(\mathrm {[L]}\)

  • ZG: real:Z position of vessel coordinate system referred in global system \(\mathrm {[L]}\)

  • DIRX: real: Direction of vessel X-axis.

Next data group is Line and segment specification.