BC Types in OrcaFlex (+2)
BC Types in OrcaFlex
| BC Type |
OrcaFlex Setting |
Engineering Scenario |
| Fixed (clamped) |
End A/B: Fixed |
Flowline tie-in, rigid flange |
| Free |
End A/B: Free |
Anchor chain free end |
| Vessel-attached |
End A/B: Connected to vessel |
Riser top, mooring fairlead |
| Anchored (pinned) |
End B: Fixed position, free rotation |
Drag embedment anchor |
| Seabed contact |
Seabed model active |
Pipeline touchdown, mooring chain |
| Mid-line constraint |
Constraint object |
Clamp, bend stiffener tip |
| Coupled structure |
Linked to another line |
Pipeline-riser junction, in-line tee |
BC Documentation Template
Boundary Conditions:
├── Top End (End A)
│ ├── Connection: Vessel "FPSO" / anchor point / fixed
│ ├── Position (x, y, z): [m, global]
│ ├── Degrees of freedom: Translational [fixed/free], Rotational [fixed/free]
│ └── Effective stiffness (if flexible connection): kx, ky, kz [kN/m]
│
├── Bottom End (End B)
│ ├── Connection: Seabed / anchor / fixed point
│ ├── Position (x, y, z): [m, global]
│ └── Chain/wire burial — effective anchor point
│
├── Seabed Model
│ ├── Type: Linear elastic / non-linear / PONDUS
│ ├── Normal stiffness: kn [kN/m/m]
│ ├── Friction coefficient: μ (axial and lateral)
│ └── Slope: θ_seabed [°]
│
└── Intermediate Constraints (if any)
├── Bend stiffener / bell mouth: position along line, stiffness curve
├── Clamps: position, gap, friction
└── Buoyancy modules: start/end KP, spacing
Common BC Mistakes to Flag
bc_checks = {
"anchor_drag_not_modelled": "End B fixed XYZ — ensure drag embedment verified separately",
"vessel_motion_missing": "End A connected to vessel but no RAOs imported — static only",
"seabed_stiffness_too_high": kn > 500, # [kN/m/m] — causes numerical issues
"friction_coeff_zero": mu_axial == 0.0, # Under-conservative for walking
"free_end_tension_check": end_tension < 0, # Negative = compression — flag
}
1---2name: fe-analyst-bc-types-in-orcaflex3description: Sub-skill of fe-analyst: BC Types in OrcaFlex (+2).4---56# BC Types in OrcaFlex (+2)78## BC Types in OrcaFlex91011| BC Type | OrcaFlex Setting | Engineering Scenario |12|---|---|---|13| Fixed (clamped) | End A/B: Fixed | Flowline tie-in, rigid flange |14| Free | End A/B: Free | Anchor chain free end |15| Vessel-attached | End A/B: Connected to vessel | Riser top, mooring fairlead |16| Anchored (pinned) | End B: Fixed position, free rotation | Drag embedment anchor |17| Seabed contact | Seabed model active | Pipeline touchdown, mooring chain |18| Mid-line constraint | Constraint object | Clamp, bend stiffener tip |19| Coupled structure | Linked to another line | Pipeline-riser junction, in-line tee |202122## BC Documentation Template232425```26Boundary Conditions:27├── Top End (End A)28│ ├── Connection: Vessel "FPSO" / anchor point / fixed29│ ├── Position (x, y, z): [m, global]30│ ├── Degrees of freedom: Translational [fixed/free], Rotational [fixed/free]31│ └── Effective stiffness (if flexible connection): kx, ky, kz [kN/m]32│33├── Bottom End (End B)34│ ├── Connection: Seabed / anchor / fixed point35│ ├── Position (x, y, z): [m, global]36│ └── Chain/wire burial — effective anchor point37│38├── Seabed Model39│ ├── Type: Linear elastic / non-linear / PONDUS40│ ├── Normal stiffness: kn [kN/m/m]41│ ├── Friction coefficient: μ (axial and lateral)42│ └── Slope: θ_seabed [°]43│44└── Intermediate Constraints (if any)45 ├── Bend stiffener / bell mouth: position along line, stiffness curve46 ├── Clamps: position, gap, friction47 └── Buoyancy modules: start/end KP, spacing48```495051## Common BC Mistakes to Flag525354```python55bc_checks = {56 "anchor_drag_not_modelled": "End B fixed XYZ — ensure drag embedment verified separately",57 "vessel_motion_missing": "End A connected to vessel but no RAOs imported — static only",58 "seabed_stiffness_too_high": kn > 500, # [kN/m/m] — causes numerical issues59 "friction_coeff_zero": mu_axial == 0.0, # Under-conservative for walking60 "free_end_tension_check": end_tension < 0, # Negative = compression — flag61}62```6364---
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