Copyright of Shell Oil Company. All rights reserved. This presentation is classified as ECCN EAR99.

1September 2010

Simulation of fluid-structure interaction to estimate fatigue life of subsea pipeline spans

Juan P. Pontaza

Shell Projects & TechnologyHouston, TX

10th Symposium on Overset Composite Grids and Solution Technology

September 20 – 23, 2010

Copyright of Shell Oil Company. All rights reserved.This presentation is classified as ECCN EAR99.

2September 2010

OUTLINE

Background

Vortex-Induced Vibrations (VIV) of subsea pipeline spans

Motivation / Numerical Methods / Scope

Modeling Fluid-Structure Interaction (FSI)

Field application: A crossing pipeline span

Concluding Remarks

Copyright of Shell Oil Company. All rights reserved.This presentation is classified as ECCN EAR99.

3September 2010

BACKGROUND: VIV of Pipeline Spans

Vortex-Induced Vibrations

External flow about offshore structures Frequency synchronization (lock-in)

Fatigue damage

Integrity of subsea pipelines

TLP

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Copyright of Shell Oil Company. All rights reserved.This presentation is classified as ECCN EAR99.

4September 2010

BACKGROUND: VIV of Pipeline Spans

Widespread solutions to suppress VIV

Helical strakes Prevents near-wake interaction of shear-layers

Spanwise de-correlation of vortices

Some fixed separation points

Increased drag coefficient

Fairings Flow streamlining

Free to weathervane

Low drag coefficient

Unstable for certain Chord/D

Copyright of Shell Oil Company. All rights reserved.This presentation is classified as ECCN EAR99.

5September 2010

BACKGROUND

Motivation

Numerical simulation → Prediction → Better assessment of risk

Numerical methods

Block-structured grids / Overset grids

Incompressible flow

Finite difference / Finite volume hybrid scheme

Discretization in (ξ,η,ζ)

LES & URANS turbulence models

Level-set methods for two-phase flows

Scope

Asset / Pipeline structural integrity in the presence of fluid flow

Copyright of Shell Oil Company. All rights reserved.This presentation is classified as ECCN EAR99.

6September 2010

MODELLING FSI

Fluid & Structure coupling

Flow solver/Structural solver/Hole cutter

Structural solver receives instantaneous flow-induced loading

Flow solver receives instantaneous displacement

CSS vs. SLIK

Structural Solver

Flow Solver

12 34

Copyright of Shell Oil Company. All rights reserved.This presentation is classified as ECCN EAR99.

7September 2010

MODELLING FSI: Validation (1/3)

pulley top frame

weight to compensate top assembly

Bending load celland sleeve

Upper ball jointCurrent

Test tubular

Lower ball jointBending load cell

Bottom plate

Caisson

Experimental setup Numerical model

Hinged end condition

Pinned end condition

JP Pontaza, RG Menon. OMAE Conference Proceedings. OMAE2009-79150.

Copyright of Shell Oil Company. All rights reserved.This presentation is classified as ECCN EAR99.

8September 2010

MODELLING FSI: Validation (2/3)

Comparison with experimental measurements

RMS of cross-flow motion RMS of in-line motion

Copyright of Shell Oil Company. All rights reserved.This presentation is classified as ECCN EAR99.

9September 2010

MODELLING FSI: Validation (3/3)

Comparison with experimental measurements

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Flow

Response frequency

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Copyright of Shell Oil Company. All rights reserved.This presentation is classified as ECCN EAR99.

10September 2010

CROSSING SPAN: Structural Model

Pipe is modeled as a beam subject to unsteady three-dimensional flow-induced loads

Nonlinear strain measures: Coupling of in-line, cross-flow, and axial degrees-of-freedom

Soil is modeled as an elastic foundation, with stiffness values from field measurements

JP Pontaza, RG Menon. OMAE Conference Proceedings. OMAE2010-20804.

Copyright of Shell Oil Company. All rights reserved.This presentation is classified as ECCN EAR99.

11September 2010

CROSSING SPAN: Fluid Flow Model (1/2)

Near-wall spacing of Δs/D = 10-5 at all no slip surfaces (seabed & pipe)

180 cells around the circumference of the pipe Large Eddy Simulation (LES), 17 MM grid points

Copyright of Shell Oil Company. All rights reserved.This presentation is classified as ECCN EAR99.

12September 2010

CROSSING SPAN: Fluid Flow Model (2/2)

Uref based on metocean data for extreme sea bottom current event Reynolds number, Re = 4.94×104

Reduced velocity, U* = Uref f/D = 3.1

Copyright of Shell Oil Company. All rights reserved.This presentation is classified as ECCN EAR99.

13September 2010

CROSSING SPAN: Ignoring flow blockage

Idealized scenario where flow blockage is ignored

As expected, in-line VIV is significant and dominates the fatigue life

Copyright of Shell Oil Company. All rights reserved.This presentation is classified as ECCN EAR99.

14September 2010

CROSSING SPAN

Flow blockage effects

A localized gap effect at the crossing is present

CONCLUDING REMARKS