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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
-1 -0.75 -0.5 -0.25 0 0.25 0.5 0.75 1-1
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-1 -0.75 -0.5 -0.25 0 0.25 0.5 0.75 1-1
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x/D
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-1.25 -1 -0.75 -0.5 -0.25 0 0.25 0.5 0.75 1 1.25-1.25
-1
-0.75
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x/D
y/D
U* = 2.20
U* = 4.00
U* = 5.00
Flow
Response frequency
Sim
ulat
ion
Expe
rimen
ts
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