Pipeline Dynamics with Flowing Contents in Abaqus/Standard · Pipeline Dynamics with Flowing...
Transcript of Pipeline Dynamics with Flowing Contents in Abaqus/Standard · Pipeline Dynamics with Flowing...
Pipeline Dynamics with Flowing Contentsin Abaqus/Standard
Dr. Barry TrippitSimuserv, Perth, Australia
Coauthors
Kin Yin Chee, INTECSEA, Perth, Australia
Sinan Aizad, Simuserv, Perth Australia
Barry Trippit Slide 2
Overview
Simuserv the company
Why model pipeline contents
Existing approaches
New concept
Sleeper example
Spool example
Benefits & Limitations
Novel applications
Summary
Barry Trippit Slide 3
Simuserv
Dassault Systemes PLM Solution Partner and Education Partner for SIMULIA solutions in Australia
Provision of advanced Simulation Services
Offices in Melbourne and Perth
Experience across a range of industries Automotive Packaging Railway Aerospace Mining Oil & Gas
Perth
Melbourne
Barry Trippit Slide 4
Oil and Gas
Significant Oil and Gas developments in Australia
Abaqus primarily used for: Subsea pipeline buckling Pipeline walking Pipeline installation
Simuserv Abaqus customisations Various Pipeline to Seabed friction models Wave loading
Interest in modelling changing pipeline mass Some complexity in achieving this
Barry Trippit Slide 5
Slugging
Reservoirs produce mixture of: Fluid (Oil, Condensate, Water)
Gas
Mix varies with conditions and reservoir life
Products transported in single pipeline
Flow condition within a pipe: Low velocity – separate but even High velocity – mixed Intermediate velocity slugging can
occur Fluid forms slugs gas forms bubbles
Courtesy Cooper, P. “Fatigue Design of Flowline Systems with Slug Flow”, 28th International Conference of Ocean, Offshore and Arctic
Engineering, 2009
Barry Trippit Slide 6
Slugging
Occurs naturally Develops from uniform inflow conditions Sizing of pipes is conducent to slug flow
8m/s, 75% fluid
Actual condition highly variable Perhaps 60m slug followed by 20m bubble Perhaps 1 slug per 10 seconds
Slug significantly more dense Perhaps 900 vs. 100 kg/m3
Fatigue concerns Pipeline free spans Sharp bends
Three effects: Changing weight/loading Momentum changes Inertia changes
Barry Trippit Slide 7
Modelling Changing Mass
Ideally want to model this in Abaqus/Standard Model effect of density change without fluid detail However no convenient method to change/transport mass
Potential Approaches: Moving distributed load, perhaps DLOAD routine
Captures weight Ignores inertia and perhaps momentum
Activate/deactivate additional masses Captures weight and inertia Ignores momentum Multiple steps cumbersome
Transport masses, perhaps with slideline contact Captures weight, inertia, momentum Contact iterations (no tied option) Mass movement cumbersome
Barry Trippit Slide 8
MPC User Routine
MPC routine supports implementation of arbitrary nonlinear constraint equations
Concept: Create moving tie constraint to transport additional mass along the path of the pipeline at a predefined speed
Extra mass node is slave All pipeline nodes define path and are potentially masters Couple slave only to close masters Slave location updated and moves along path
Use many constraints to tie many masses to form slug
Slave Mass
Coupled MastersCoupled Masters Coupled Masters
1 432
Potential MastersPipe Elements
Barry Trippit Slide 9
Simple Test
Cantilever beam Single coupled heavy mass element Gravity loading Dynamic analysis
………*MPC,USER,MODE=NODE1100,100,1,2,3,4,5**………***STEP,NLGEOM*DYNAMIC0.01,1.0,,0.01***FIELD,VARIABLE=1100,-10.0***END STEP
Barry Trippit Slide 10
Constraints
Lateral constraint: Linear between master nodes in current segment Investigating option of cubic
Significantly more complex
Axial constraint options: 1. Defined speed relative to pipeline, forces reacted to pipeline 2. Defined speed relative to pipeline, forces reacted to ground 3. Slider
1 432
Slave Mass
Coupled Masters
Barry Trippit Slide 11
Pipeline Sleeper
Sleepers form buckle initiators Relieves thermal strains 0.5m high sleeper, 300m of pipeline modelled Potential slug induced fatigue
Four consecutive slugs modelled 60m long slug, 600 masses per slug, 600 user MPC’s 8m/s slug velocity Dynamic implicit analysis
View almost along axisPipe shown smaller than realInstallation steps not shown
Barry Trippit Slide 12
Pipeline Sleeper
Response mostly quasi-static Sag due to weight change most important
Significant free span changes Varies between 27 and 72m, original 60m
Significant stress cycles Double peaked response
Maximum peak with central slug Smaller peak central bubble Trough with slug to side Initial and final gas only
Barry Trippit Slide 13
Jumper Spool
Connects various subsea equipment Maybe supported only at ends Potential for slug induced fatigue
Four consecutive slugs modelled 60m long slug, 600 masses per slug 8m/s slug velocity
Jumper Spool
Barry Trippit Slide 14
Jumper Spool
Static & Dynamic Highly damped Less damped
Higher dynamic stresses Change in momentum at
corners
Some vibrations present Real damping unknown
SlugPosition
Static
DynamicHighly
Damped
DynamicLess
Damping
Displacements x50
Barry Trippit Slide 15
Benefits
Relatively easy user setup *MPC bit cumbersome for many MPC’s
Easily automated
Velocity and path easily defined
Reasonably efficient even with many slaves Small time steps can be required for dynamic
Captures all desired effects
Barry Trippit Slide 16
Limitations
Masses traversing a bend, ideal stepping
Masses continually moving
Barry Trippit Slide 17
Limitations
MPC routine called for three purposes:1. Define slave degrees of freedom
Position slave nodes
2. Transfer loads from slave to masters
Constraint equilibrium
3. Eliminate slave from stiffness matrix
Convergence of Newton iteration
Abaqus assumes derivatives for 2 and 3 are same Appropriate for many constraints
In this case causes non-quadratic convergence
Although no issues observed to date (small steps)
Masters controlling axial position(convergence)
Load transfer masters
(constraint equilibrium)
1 2 43
For convergence of axial position derivatives will have terms from nodes 1 and 2For correct force transfer derivatives will have terms from nodes 2 and 3 only
Barry Trippit Slide 18
Novel Applications
Movement of nodes along path and connected to body Moving loads/mass, similar to slideline (without contact)
Transport of mass with stationary stiffness Semi-eulerian
Mass elements transported while stiffness elements held stationaryContact with rollers/pulleys essentially unchanging
Same as pipeline
Barry Trippit Slide 19
Summary
Slugging occurs naturally in many subsea pipelines
Potential for fatigue damage at various locations, this is a design driver
Abaqus capable of solving slugging User MPC routine developed to conveniently model the phenomenon
Thanks to Co-authors INTECSEA