Node Number and Coordinates (Data Category 1)

The function of this data category is to define a table of coordinate positions on the structure or fixed in space, referred to in later data categories, e.g. Element Topology (Data Category 2) used for modeling the structure. These positions are referred to in the documentation as nodes. A node is defined by an integer number (called a node number) and three Cartesian coordinates which are associated with this number.

The node number is used only as an index to the values of the coordinate positions and therefore may be any numbers which are convenient to the user. Node numbers do not have to be in any order, se-quenced, or referenced by another data category.

Node numbers must be unique.

Although the user will find that a series of random integers is quite valid, the hydrodynamic and hydro-static modeling of the structure in Data Category 2 can be made considerably easier by a logical ordering of the node numbers.

For 32-bit Aqwa, there can be up to 22000 nodes explicitly defined, or 44000 if one symmetry data record is used, or 88000 if two symmetry data records are used. For 64-bit Aqwa, there can be up to 46000 nodes explicitly defined, or 92000 if one symmetry data record is used, or 184000 if two symmetry data records are used.

When The STRC Data Record - Coordinate Structure Association (p. 36) (STRC) is not used, the coordinate positions in this data category are not specifically associated with any one structure nor with any one element within that structure. This means that many elements may reference the same node number and several structures may also reference the same node number. This does not mean that the structures are joined together at a node, but that the structures are completely independent unless specified otherwise (for example, Data Category 12 (Constraints) and Data Category 14 (Mooring Lines)). When a structure moves, the node moves with the structure.

When used,The STRC Data Record - Coordinate Structure Association (p. 36) (STRC) provides a means to associate particular nodes with individual structures.

5.2. Data Category Header

-- | | | |

| |_Compulsory Data Category Keyword(A4) |

|_Optional User Identifier(A2)

5.3. The Coordinate Data Record

(1) This is the node number (N1) whose coordinate position is given by the values X, Y, Z (4).

(2) Leave blank (as in first data record shown above) if only 1 node is to be generated. A total of N2 nodes are generated automatically if this number (N2) is greater than 1. The Nth node is generated:

with a node number N1+ (N-1)N3

with coordinates X+(N-1)DX, Y+(N-1)DY, Z+(N-1)DZ

(3) Leave blank (as in first data record shown above) if only one node is to be generated. If this field is left blank when generating nodes, then a value of 1 is assumed for this Nodal Increment (N3).

(4) Coordinate Position (X,Y,Z) associated with node number N1 (1).

(5) Leave blank (as in first data record shown above) if only 1 node is to be generated. These 3 values are referred to as DX,DY,DZ in (2).

5.4. The Coordinate Data Record with Rotational Node Generation

This facility may be used to generate nodes by rotating nodes already input by a specified angle about a specified position. This is particularly useful for describing the nodes on axisymmetric bodies.

2 5 7 11 16 21 31 51 61 71

| | | | |_(3)Number of Nodal Sets to be Generated(I5)(Default 1) | | | |

| | | |_(2)The User node number of the 1st node in a set.

| | |

| |_Compulsory END on last data record in data category |

|_(1)Indicates Rotational Node Generation

(1) This single letter code indicates that a set of nodes is to be generated by rotating a set of nodes already input.

(2) This is the starting node of the set to be copied (input sequence = NS1). The finish node of the set is the last node input so far (input sequence = NF1).

(3) This is the number of node sets to be generated (NSETS). The total number of nodes automatically generated in addition to those already input is given by:

Total additional nodes = NSETS (NF1-NS1+1)

If this field is left blank, or zero is input, NSETS=1 is assumed.

(4) This node increment number (N3) is the number by which the node numbers already input are to be incremented. In other words, if the nodes previously input are numbered NP1, NP2, NP3 etc., and the new node numbers are NN1, NN2, NN3 etc., these new node numbers are given by:

NN1 = NP1 + N3; NN2 = NP2 + N3; NN3 = NP3 + N3; etc.

If no increment value is present, or zero is input, the program will issue a warning and default to a value of 100.

(5) These three values are the coordinates of the point about which the rotation of the nodes already input takes place. This field may be left blank, in which case the point is assumed to be 0.0, 0.0, 0.0, i.e.

the FRA origin.

(6) These three values (RX,RY,RZ) are the components of the angular vector of rotation, i.e. the angle and axis about which the rotation takes place is given by

Angle = modulus (RX,RY,RZ)

Axis = vector (RX,RY,RZ) / Modulus (RX,RY,RZ)

Although this means that the user has the facility to generate nodes rotated about any axis, the most common usage is as follows (using 30 degrees as an example)

Rotation about X-axis RX = 30.0 RY = 0.0 RZ = 0.0 Rotation about Y-axis RX = 0.0 RY = 30.0 RZ = 0.0 Rotation about Z-axis RX = 0.0 RY = 0.0 RZ = 30.0

EXAMPLE

Generation of nodes for six, 50m tall, 8m diameter cylindrical legs of an axisymmetric semi-submersible at a radius of 75 metres

The Coordinate Data Record with Rotational Node Generation

2 5 7 11 16 21 31 41 51 61 71 - --- -- ---- --- --- | | | | 1| 6| 1| 79.0 | 0.0 | 0.0 | 0.0 | 0.0 | 10.0 | - --- -- ---- --- --- |R| | | | 12| 10| 75.0 | 0.0 | 0.0 | 0.0 | 0.0 | 30.0 | - --- -- ---- --- --- --- --- --- --- --- --- |R| | | | 5| 200| 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 60.0 | - --- -- ---- --- ---

---Data Record 1 - Generates six nodal coordinate on a vertical line.

Data Record 2 - Generates 12 additional vertical lines at 30 degree intervals; that is, generates the nodes to define a single cylinder. Note that the last set of nodes (121-126) have the same coordinates as the first set (1-6). This makes the numbering sequential for all 12 faces of the regular dodecagon representing the circular surface and hence facilitates the specification of element topology (Data Category 2).

Data Record 3 - Generates five additional cylinders at 60 degree intervals.

Total number of nodes generated (see columns 11 to 15) is 6 (12+1) (5+1) = 468

5.5. The STRC Data Record - Coordinate Structure Association

The STRC (structure) data record enables the use of totally independent sets of coordinates for each structure. In other words, the USER node numbers may be the same for 2 different structures but they will be treated as separate items. The STRC data item can also be utilized in the Material and Geometric property data categories; see note below.

Fixed nodes (referred to as Structure 0) must be defined in the nodes of the structure which is connected to them, for example:

• Fixed nodes for mooring lines from Structure 1 to Structure 0 must be defined in the Structure 1 set of co-ordinates

• A fixed node for an articulation connecting Structure 2 to Structure 0 must be defined in the Structure 2 set of coordinates.

• Similarly for connections between other structures and Structure 0.

Note

• If the STRC data record is not used all user node numbers must be unique.

• If the STRC data record is used in the COOR data category, then it may also be used in the MATE and GEOM data categories if the use of the same property number is required from different structures.

• If the STRC data record is not used in the COOR Data Category, it cannot be used in the MATE(materials) and GEOM(geometry) Data Categories.

The structure number has to be in columns 16-20 as shown below:

5 7 16 21 - --- -- -- - X XXX 01 STRC XXXXX nn XXXXXX - --- -- -- - | | |

Node Number and Coordinates (Data Category 1)

| | | | | |

| | |_(3)Structure Number.

| |

| |_(2)Mandatory data record keyword.

|_(1)Optional user data category identifier

(3) The structure number must start from 1 on the 1st data record and increment by 1 for each structure data record input. The number of ELM* data categories must correspond to the number of structure data records.

5.6. The Coordinate Data Record with Offset

The OFFSET data record is in the following format:

6 16 21 31 41 - --- -- --- O XXX 01 XXXXXXX 100 10.0 0.0 0.0 - --- -- --- | | | | | |

| |_(2)Optional user data category identifier |

|_(1)Compulsory data record keyword (A1) NB:O = Absolute offset o=relative

(1) Note that upper case 'O' will define an absolute offset and lower case 'o' will define a relative offset.

All node coordinates input after this data record will be generated offset by these 3 values.

For example, if the nodes for 3 identical legs along the X axis, 30m apart, with the 1st leg at X = 5.0 are defined, then the 2 absolute X offset data records input just before the node coordinate for legs 2 and 3 would be 35.0,65.0. The 2 relative X offsets would be 30.0,30.0, as the default offset is zero.

Note

If a STRC data record (The STRC Data Record - Coordinate Structure Association (p. 36)) is input, the OFFSET will automatically be re-set to zero.

5.7. The Coordinate Data Record with Translation

This facility may be used to generate nodes by translating nodes already input by a specified transla-tional increment:

2 5 7 11 16 21 31 41 51 61 71 - --- -- ---- --- --- ---- ---- --- - -- |T| | |1 | 3| 100|XXXX|XXXX|XXXXX| 30.0 | 0.0 | 0.0...

- --- -- ---- --- --- -- -- -- -- | | | | | | | | | | | | | | | | | | | | | |

| | | | | |_(4)Increment for Each set of Node Numbers(I5)

The Coordinate Data Record with Translation

| | | | |

| | | | |_(3)Number of Nodal Sets to be Generated(I5)(Default 1) | | | |

| | | |_(2)The User node number of the 1st node in a set.

| | |

| |_Compulsory END on last data record in data category |

|_(1)Indicates Translational Node Generation

(1) This single letter code indicates that new sets of nodes are to be generated by translating a set of nodes already input.

(2) This is the starting node of the set (input sequence = NS1). The finish node of the set is the last node input so far (input sequence = NF1).

(3) This is the number of node sets to be generated (NSETS). The total number of nodes automatically generated in addition to those already input is given by:

Total additional nodes = NSETS (NF1-NS1+1)

If this field is left blank, or zero is input, NSETS = 1 is assumed.

(4) This node increment number (N3) is the number by which the node numbers already input are to be incremented. In other words, if the node set previously input are numbered NP1, NP2, NP3, etc., and the new node numbers are NN1, NN2, NN3, etc., these new node numbers are given by:

NN1 = NP1 + N3; NN2 = NP2 + N3; NN3 = NP3 + N3

If no increment value is present, or zero is input, the program will issue a warning and default to a value of 100.

(5) This node coordinate increment number (DX,DY,DZ) is the VALUE by which the node set coordinates are to be incremented; that is, if the node set previously input are values XP1, XP2, XP3 etc and the new X coordinates XN1, XN2, XN3, etc, these new values are given by:

XN1 = XP1 + DX; XN2 = XP2 + DX; XN3 = XP3 + DX Similarly for Y and Z.

5.8. The Coordinate Data Record with Mirror Node Generation

This facility may be used to generate nodes by reflecting nodes already input in a specified plane.

2 5 7 11 16 21 31 41 51

- --- -- ---- --- --- M|END| | 101| XXXX| 100| 1.0 | 1.0 | 2.0 | 15.0 | - --- -- ---- --- --- | | | | | | | | | | | | | | | | | | | |

| | | | |

| | | | |_(3)Increment for each set of Node Numbers(I5) | | | |

| | | |_(2)The User node number of the 1st node in a set.

| | |

| | |_Optional User Identifier(A2)

Node Number and Coordinates (Data Category 1)

| |

| |_Compulsory END on last data record in data category |

|_(1)Indicates Mirror Node Generation

(1) This single letter code indicates that a set of nodes is to be generated by reflecting a set of nodes already input.

(2) This is the starting node of the set to be copied (input sequence = NS1). The finish node of the set is the last node input so far (input sequence = NF1). The number of nodes generated will always be (NF1-NS1+1).

(3) This node increment number (N3) is the number by which the node numbers already input are to be incremented. In other words, if the nodes previously input are numbered NP1, NP2, NP3, etc., and the new node numbers are NN1, NN2, NN3, etc., these new node numbers are given by:

NN1 = NP1 + N3; NN2 = NP2 + N3; NN3 = NP3 + N3; etc.

If no increment value is present, or zero is input, the program will issue a warning and default to a value of 100.

(4) These are the co-efficients A, B, C, D which define the plane of reflection. The plane is defined by the equation:

Ax + By + Cz = D

5.9. The NOD5 Data Record - 5-digit node numbers

This data record allows node numbers with 5 digits to be defined directly.

The input format is as follows:

5 7

- --- -- ---- X|XXX| |NOD5|XXXXX - --- -- ---- | |

| | | |_(2) |

|_(1)Optional user data category identifier

When the NOD5 data record is used the format for all following coordinate data records are changed slightly as shown below. The field for node numbers becomes 5 columns, while the field for the number of generated nodes is reduced to 4 columns. All the other fields are unchanged.

2 5 7 12 16 21 31 51 61 71 - --- -- --- ---- --- -- -- -- -- -- |X| | | 4| | | 54.6 | ... | | | ...

- --- -- --- ---- --- -- -- -- -- -- |X|END| | 23| 3| 10| 54.6 | ... | 4.5 | | ...

- --- -- --- ---- --- -- -- -- -- -- | | | | | |

| | | | | |_(4)3 Coordinates for Start Node (3F10.0) | | | | |

The NOD5 Data Record - 5-digit node numbers

| |_Optional User Identifier(A2) |

|_Compulsory END on Last Data Record in data category (A3)

Node Number and Coordinates (Data Category 1)

In document Aqwa Reference Manual (Page 43-51)