Coupling of Cable FEA Solution With 6 DOF CFD Solution for Subsea Equipment Launching Simulation

Fabio Saltara Roberto Monteiro Basto da Silva Ricardo Barbosa Damian Ismael Lis Alves Daoud Armando Alvarez de Souza Regis Ataides

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Problem Description

Subsea Equipment Launching Simulation

Alternatives:

- AQWA-FLUENT coupling

- Structural ANSYS – FLUENT coupling

- FLUENT User Defined Function (UDF) Solution

Problem Description

Methodology – FEA Solution

cablesdragbuoyancyweightmassaddedinertia FFFFFF

cablesdragdAA

a FFgmmt

tdttdmm

2

ma = added mass

md = displaced fluid mass

Methodology – FEA Solution (2D Formulation)

yneighbour

xneighbour

yA

xA

o

d

d

d

d

mlmmlm

lmllml

L

EAdK

22

22

L

xxl

L

yym

AneighbourAneighbour

L

txtx

L

LLEAFgmmttdK

t

tdttdmm

Aneighbour

cables o

odragd

cables

AAa

)()(

2

Where:

Methodology – 6DOF and FEA Coupling

connectors

bodyichydrodynamext TgmFF

connectors

ichydrodynamext TrMM

,,,6

CGCGDOF

xx

trxd CGconnectors

Case 1

Case 1

26,022 cells

11,622 triangular cells

14,400 quadrilateral cells

t=0.01 s

Spalart-Allmaras Turbulence

Model

Final Time: 118 s

Boundary Conditions

Deforming + Remeshing Methodology

- After five time-steps the triangular cells are remeshed;

- At each time-steps the mesh is deformed according to a displacement diffusion methodology:

.boundarynearestthetodistancetheisawhere,1

;velocitymeshtheiswhere

0

2a

W

x

W

x

i

j

i

j

Results - Case 1

Results - Case 1

Case 2

Final time around 265 s. Mesh and other settings are the same of Case 1.

Results - Case 2

Results - Case 2

Conclusion

It was demonstrated that it is possible to use a FLUENT User Defined Function (UDF) for the FEA solution of the cable forces and displacements during the simulation of the pendulum motion that is a feature of the launching of subsea equipment and it is feasible to run a full CFD simulation of this type of operation.

Next Steps

• Development of the full 3D methodology ( involves only changing the [K] matrix );

• Evaluation of other turbulence models;

• Evaluation of other moving mesh methodology (could all mesh be considered as having rigid body motion?);

• Parallelization of the UDF;

• Mesh generation for a 3D case.