All lines have a vertical offset of 0.75 m below their connection
point (-0.75 m in z direction). The lines are numbered
from 1 to 8 in Figure A4.4. Lines 1 to 4 are connected
to the left connection and lines 5 to 8 are connected to
the right connection.
Lines 1 to 4 are connected with a horizontal offset (in ydirection)
of respectively -0.25 m, 0.75 m, 1.75 m and 2.75
m with respect to the left connection point. Lines 5 to 8
are connected with a horizontal offset (in y-direction) of
respectively -3.75 m, -2.75 m, -1.75 m and -0.75 m with
respect to the right connection point.
By applying the lines in this way beneath each section of
the boom, it is possible to get a continuous Array of lines
for the skirt. The possibility of connecting the lines to 6D
Buoys with an offset reduces the calculation time significantly
in comparison to placing a 6D Buoy for every line
that needs to be connected to the boom.
It is possible to do this because the steel sections themselves
are so rigid that no important relative displacements
will take place between the top of the vertical lines
and the point on the steel section where they should actually
be connected to.
The lines have the following properties (as determined
from tests done to optimize ballast and skirt thickness
for further simulations). See also subchapter 3.5
• Length: 1.0 m
• Diameter: 5.0 *10-3 m
• Mass per unit length: 2.9*10-3 t/m
• Bending stiffness: 0.292 kNm²
• Axial stiffness: 3.5 kN
• Poisson ratio: 0.50
• Torsional stiffness: 10 kNm²
• X drag coefficient: 0.1 (the x direction of the lines is 00
defined in the skirt plane, perpendicular to the line)
• Y drag coefficient: 1.2 (the y direction of the lines is
defined normal to the skirt plane, perpendicular to the
line)
• Z drag coefficient: 0.1 (the z direction is the axial
direction of a line)
• Drag diameter: 0.6 m
• Added mass coefficients: 0.01 in x and z direction;
1.0 in y direction
• Number of segments: 2