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Bend stiffener model with separate helices

The input to this model can be found in the example folder, under case E004.

A section of flexible pipe with bend stiffener is defined. The model is rigidly fixed in all degrees of freedom at the top/root of bend stiffener. The pipe is exposeed to

  • tension applied at the lower end

  • external and internal pressure

  • bending; applied by transverse loading at the lower end

E004 model
Figure 1. Bflex model

Model description

The model is similar to the one with pipe52 elements, except that the tensile armour is modelled using hshear352 elements. These elements have degrees of freedom in the axial direction of the helix system. End effects related to anchoring of tensile wires at terminations can then be captured. The model is shown in Figure 1, and consists of thermal layers, carcass and zeta spiral that are specified based on the cross sectional area and with no detailed geometry. The bend stiffener is included selecting type nlbendstiff-bend. This means that no axial and torsional stiffness is introduced from the bend stiffener, only bending stiffness is accounted for.

To include the hshear352 elements, separate helical nodal systems must be generated:

#      no      x0    y0   z0   b1   b2   b3    R       node    xcor      theta
NOCOOR  POLAR  0.0   0.0  0.0  0.0  0.0  0.0   103.604 10001   0.0       0.0   
                                                       10301   30.0E+03  169.05
#       n  ninc   dx        dtheta
Repeat 16  301    0.0       0.392      
#
#      no      x0    y0   z0   b1   b2   b3    R       node    xcor      theta
NOCOOR  POLAR  0.0   0.0  0.0  0.0  0.0  0.0   109.798 20001   0.0       0.0
                                                       20301   30.0E+03 -161.94
#       n  ninc   dx        dtheta
Repeat 16  301    0.0       0.392      
#

The elements are defined similar to the pipe52 elements, but must reference both the helix nodes and corresponding center nodes:

ELCON  NYETENSILE1  hshear352   NYEMAT   10001  1     2    10001  10002              
                                         10016  1     2    14516  14517
#       n   elinc  nodinc
Repeat  300   16        1


ELCON  NYETENSILE2  hshear352   NYEMAT   20001  1     2    20001  20002              
                                         20016  1     2    24516  24517
#       n   elinc  nodinc
Repeat  300   16        1
#

The end points of the helices must be constrained in some way, for example by boundary conditions:

#
BONCON GLOBAL 10001      1
repeat 16 301
BONCON GLOBAL 10301      1
repeat 16 301
#
BONCON GLOBAL 20001      1
repeat 16 301
BONCON GLOBAL 20301      1
repeat 16 301
#

Results

The curvature profile is obtained by glplot from bflex2010post, and shown at maximum displacement in Figure 2. The solid line represents the current model, while the dashed line is from a pure pipe52 model.

E004 curvature
Figure 2. Curvature profile

Relevant files

Go to bflex2010 file

Go to bflex2010post file

User manual for reference

Processing of files from command line

  • bflex2010 -n bflex2010_01

  • bflex2010post -n bflex2010post_01

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