Flexible pipe with carcass and pressure spiral
The input to this model can be found in the example folder, under case E010.
A section of flexible pipe and bend stiffener is modelled.
Model description
The flexible pipe model, see Figure 1, Figure 2 and Figure 3, consist of thermal layers, carcass and zeta spiral and tensile armours.
| In this model the itcode is set to 21, which will apply one moment-curvature curve. If itcode is set to 31, then one moment-curvature for each layer is applied. |
Detailed geometry of the carcass and pressure spiral are specified, using crossgeom input:
# name x0 y0 ccurv p1 p2 p3 p4 ninter icode
CROSSGEOM ZETA-FLEXARM BFLEX 0 0 S 3.0909 0.0000 0.0 0.0 8 0
CI 95.000 189.00 0.4032 0.0 4 0
S 2.8308 92.000 0.0 0.0 6 0
CI 189.00 270.00 0.2688 0.0 4 0
S 0.5624 180.00 0.0 0.0 4 2
CI 270.00 351.00 0.2688 0.0 4 0
S 0.5624 261.00 0.0 0.0 4 0
CO 171.00 90.000 0.2688 0.0 4 0
S 1.1640 180.00 0.0 0.0 4 3
CO 90.000 9.0000 0.2688 0.0 4 0
S 3.2930 92.000 0.0 0.0 6 0
CI 189.00 270.00 0.5376 0.0 4 0
S 8.8776 180.00 0.0 0.0 15 1
CI 270.00 369.00 0.6720 0.0 4 0
S 2.8119 273.00 0.0 0.0 4 0
CI 9.0000 90.000 0.2688 0.0 4 0
S 0.5624 0.0000 0.0 0.0 4 2
CI 90.000 171.00 0.2688 0.0 4 0
S 0.5624 81.00 0.0 0.0 4 0
CO 351.00 270.00 0.2688 0.0 4 0
S 1.1558 0.0000 0.0 0.0 4 3
CO 270.00 189.00 0.2688 0.0 4 0
S 2.9909 276.00 0.0 0.0 6 0
CI 9.0000 90.000 0.5376 0.0 4 0
S 5.9311 0.0000 0.0 0.0 22 1
| If you use FlexEdit, then there is a possibility to plot the boundary of the crossgeom that you have specified. |
| The geometry of the components will be stored in .bdf .msh and .geo files. Information from the .bdf file can easily be plotted to inspect the resulting profile, an indicative example for python can be found here: |
At both the end sections, stiffer sections are added by applying stiff pipe31 elemens connected to the same nodal system as the flexible pipe. These sections can represent a termination.
In the upper section, a bend stiffener is modelled, using the same nodal system as the pipe. By selecting the nlbendsitff-bend option, the axial and torsional stiffness of the bend stiffener is neglected.
| A separate nodal system could have been applied for the bend stiffener, and contact defined between pipe and bend stiffener. |
External and internal pressure is applied, as well as a tension load in the lower end of the pipe.
The bending behaviour is imposed by rotating the upper node of the pipe, i.e. the root of the bend stiffener.
# node dof value load history CONSTR PDISP GLOBAL 1 5 0.1745 400
The model is first processed by bflex2010 that generates the bflex2010_01.raf database file. bflex2010post is then used for translating into the old bflex format, which is found in the bflex2010_01_bflex2010.raf file. It is only the flexible pipe that is represented here. This result file can further be populated by additional data in a subsequent step by boundary and pflex. Finally bpost can extract result data from the bflex2010_01_bflex2010.raf file.
| If a carcass and pressure spiral layer is present, these must be described by a geometry. Otherwise, the postprocessing into old bflex format will fail. |
boundary requires the user to define the step from when bending and friction is accounted for. In a normal case, the step for friction onset should be slightly after the time for onset of bending. Further, the time for start of bending in boundary should be at a step where there already is a small bending in the analysis model. In this case the first two steps after bending is initiated are stored in the anlysis, to prepare two relevant steps for this:
TIMECO 60.0 1.0 10.0 201.0 STATIC auto none all 50 7 1e-5 TIMECO 62.0 1.0 1.0 201.0 STATIC auto none all 50 7 1e-5 TIMECO 70.0 1.0 8.0 201.0 STATIC auto none all 50 7 1e-5 TIMECO 160.0 1.0 10.0 201.0 STATIC auto none all 50 7 1e-5
| The analysis time must be extended to capture a full bending cycle. |
Relevant files
Processing of files from command line
-
bflex2010 -n bflex2010_01
-
bflex2010post -n bflex2010post_01
-
boundary -n boundary_01
-
pflex -n pflex_01
-
bpost -n bpost_01
| boundary must be executed before pflex. |