-2315 Determining What Vortex-Induced Vibration Variables have the Maximum Effect on a Pipeline Free Span s Amplitude of Displacement with Computational Fluid-Structure Interaction Authors: Marcus Gamino Samuel Abankwa Ricardo Silva Edwin Johnson Michael Fisher Raresh Pascali Egidio Marotta, Carlos Silva Alberto Rivas
Outline Outline Objective Background (Free spans and VIV) Fluid-Structure Interaction (FSI) Assumptions Procedure Mesh Sensitivity Studies (Grid Independence) Space-Filling Design Full Factorial Design Box-Behnken Design Conclusions Questions
Objective Objective To determine the effects of different Reynolds number, Re, variables (i.e. flow velocities, change in pipe diameter, and fluid densities) on the maximum amplitude of displacement of a pipeline free span due to vortex-induced vibration (VIV).
Background Free Span A free span is a section of subsea pipeline that is not supported by the seabed. Caused by: Seabed unevenness Change in seabed topology caused by the environment Susceptible to fatigue damage from vortex induced vibration www.formshore.com http://www.neo.no/research/pipeline/xplisit.html
Background Vortex-Induced Vibration Alternate vortices develop behind the structure as the underwater current moves past the pipe This alternate vortex shedding results in structural vibrations of subsea piping components including free spans and jumpers Maximum amplitude of displacement occurs when the structure s natural frequency is the same as the vortex shedding frequency behind the structure
This vibration is a major source of concern in fatigue assessment of free spans, risers, and jumpers M-Shape Jumper Background Maximum amplitude of displacement occurs when the structure s natural frequency is the same as the vortex shedding frequency behind the structure
FSI Fluid-Structure Interaction (FSI) Analyze VIV using Computational FSI with Abaqus and STAR-CCM+ Pressures Displacements
Assumptions Assumptions single mode response (1 st mode) uniform current flow an empty pipeline zero axial tension
Procedure In Abaqus three pipeline free spans with different diameter and thickness were modeled Material: Steel Young s Modulus: 30x10^6 psi Poison s Ratio: 0.3 Outside Diameter (in.) Thickness (in.) Inside Diameter (in.) Min 8 0.8 6.4 Max 12 1.2 9.6
Procedure Mesh pipeline with C3D8R elements (8- node linear brick elements) Edges of pipeline were divided by 12 seeds Number of nodes and elements in the model equal 16,560 and 8,256 respectively
Procedure Dynamic implicit analysis Used a fixed (encastre) boundary conditions for the free span. Create an input file to import to STAR-CCM+ Mesh the free span and environment Setup physics with RANS (Reynolds average navier stokes equations) Run Co-simulation
Determine best mesh based on computational time and accuracy Used midpoint (m) values for sensitivity analysis Diameter = 10 in Grid Independence Velocity = 1.25 m / s Density = 846.848 kg / m 3 ρ m velocity Diameter
Grid Independence Run Number of Base Size Cells (inches) Max Displacement (inches) Run Time 1 37051 10 2.888x10-2 approx. 1 hour 2 46029 9 2.702x10-2 approx. 1 hour 3 88378 7 2.615x10-2 approx. 1 hour and 20 min 4 242265 6 2.613x10-2 approx. 2 hours and 10 min
Space Filling Design Inputs: Velocity Range: 0.5 2 m/s Pipe Diameter Range: 8 12 inches (0.2 0.3 meters) Fluid Density Range: 696.135 997.561 kg/m^3
Space Filling Design Run Pipe Diameter (in.) Fluid Velocity (m/s) Density (kg/m^3) Displacement (in.) 1 12 1.1 937.2758 1.978x10-2 2 8 0.8 876.9906 2.215x10-2 3 11.2 2 816.7054 3.851x10-2 4 10.4 0.5 756.4202 0.7909x10-2 5 8.8 1.4 696.135 3.326x10-2 6 9.6 1.7 997.561 4.816x10-2
Space Filling Design Fluid Velocity has the greatest effect on the amplitude of the free span s displacement Change in density has the least effect
Full Factorial Design D o (in) v (m/s) ρ (kg/m 3 ) 1 8 0.5 696.135 2 8 0.5 997.561 3 8 2 696.135 4 8 2 997.561 5 12 0.5 696.135 6 12 0.5 997.561 7 12 2 696.135 8 12 2 997.561 997.561 kg/m 3 696.135 kg/m 3 0.5 m/s 12 in 2 m/s 8 in
Full Factorial Design D o (in) Displacement Values v (m/s) ρ (kg/m 3 ) X (x10-2 in) 1 8 0.5 696.135 2.215 2 8 0.5 997.561 1.334 3 8 2 696.135 7.238 4 8 2 997.561 10.36 5 12 0.5 696.135 0.6279 6 12 0.5 997.561 0.8991 7 12 2 696.135 2.943 8 12 2 997.561 4.208 Interactions
Box-Behnken Design Run Pattern Pipe Diameter (in.) Fluid Velocity (m/s) Density (kg/m^3) Displacement (in.) 1 --0 8 0.5 846.848 1.133x10-2 2 -+0 8 2 846.848 8.801x10-2 3 +-0 12 0.5 846.848 0.7626x10-2 4 ++0 12 2 846.848 3.573x10-2 5 0-- 10 0.5 696.135 0.7458x10-2 6 0-+ 10 0.5 997.561 1.066x10-2 7 0+- 10 2 696.135 4.855x10-2 8 0++ 10 2 997.561 6.951x10-2 9-0- 8 1.25 696.135 3.412x10-2 10 +0-12 1.25 696.135 1.699x10-2 11-0+ 8 1.25 997.561 4.888x10-2 12 +0+ 12 1.25 997.561 2.429x10-2 13 000 (midpoint) 10 1.25 846.848 2.615x10-2 itl.nist.gov
Box-Behnken Design
Conclusions Conclusions Fluid Velocity has the greatest effect on free span displacement when subjected to VIV Compared to velocity and pipe diameter, the change in density has very little affect on the displacement of the free span The Box-Behnkin Surface Response Design is the optimal design for this experiment, for it seems the response variations along the input ranges are nonlinear.
Future Work Use FSI methodology and other advanced computational analysis to verify assumptions made in design codes. Fatigue life analysis based on ASTM standards (e.g. ASTM E1049) may be performed in combination with the Palmgren-Miner rule to estimate the fatigue life. ASME V&V 2013
References Abaqus Version 6.7 Extended Functionality Documentations, 2007. Blevins, R.D. Formulas for Natural Frequency and Mode Shape. New York: Van Nostrand Reinhold, 1979. Chica, L., Pascali, R., Jukes, P., Ozturk, B., Gamino, M., and Smith, K. Detailed FSI Analysis Methodology for Subsea Piping Components. Proceedings of the ASME 31st International Conference on Offshore Mechanics and Artic Engineering. (2012): 1-11. DNV (2006), Free Spanning Pipeline, DNV-RP-F105. Lienhard, John H. Synopsis of Lift, Drag, and Vortex Frequency Data for Rigid Circular Cylinders. Pullman, WA: Technical Extension Service, Washington State University, 1966. Palmer, Andrew Clennel, and Roger A. King. Subsea Pipeline Engineering. Tulsa, Okla: PennWell, 2008. Recommended practice DNV-RP-F105. (2002). Free Spanning Pipelines. Hovik, Norway: Det Norske Veritas. Standard Practices for Cycle Counting in Fatigue Analysis. ASTM E1049-85(2011)e1. Star CCM+ Training. Lectures CCM+. CD-Adapco offices. Houston, TX 15 Jul. 2011.
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