Download - ABS - Sloshing Analysis
-
1Hamburg, Germany 27 September 2006
State of Art Review on LNG Containment System & Pump Tower Technology:
R&D Activities
Yung S. ShinABS Technology
Houston, TX
SMM CONFERENCE LNG SESSION
-
2Presentation topics
l Introduction - Industry Trends & Technical Issues related to LNG containment system subject to sloshing load
l Sloshing Impact Load: Analysis, model tests, scale law
l Containment system strength, vibration, fatigue: drop tests, material tests, strength tests, failure modes, structure analysis procedure including fluid structure interaction, strength assessment methodology, factor of safety
l Pump tower and base support analysis: strength, vibration, fatigue of pump tower due to sloshing, inertial and thermal loads
l Recommendations for further study
l Conclusions
-
3Introduction- Industry trends
l Increase of LNG market and surge of new shipbuilding of LNGC
l Large size of LNGC greater than 200K, 250K
l Partial filling condition vs Standard filling Operation
l New tank designs & configuration
l New analysis method, model tests, advanced strength assessment method are needed.
l Many technical issues identified
-
4ABS Sloshing Analysis
Tank Top
Insulation
C2
C1
Inner Deck
Inner BottomTank Bottom
Base Line
Pump Tower
Pump Tower
No. 2 Tank for Sloshing Analysis
LNG Ship, Tank Configuration, Pump Tower
-
5ENVIRONMENTAL CONDITIONS
Design Environments:
Unrestricted Services: North Atlantic Waves
Offshore Offloading Services: Site-Specific Waves
Wave Scatter Diagrams:
Unrestricted Services: IACS Recommendation No. 34
Site-Specific Services: ABS GSOWM data
Wave Spectrum:
Bretschneider or Jonswap Spectrum
Hs (m) 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 14.5 15.5 16.5
0.5 1.3 133.7 865.6 1186.0 634.2 186.3 36.9 5.6 0.7 0.1 0.0 0.0 0.0 0.01.5 0.0 29.3 986.0 4976.0 7738.0 5569.7 2375.7 703.5 160.7 30.5 5.1 0.8 0.1 0.02.5 0.0 2.2 197.5 2158.8 6230.0 7449.5 4860.4 2066.0 644.5 160.2 33.7 6.3 1.1 0.23.5 0.0 0.2 34.9 695.5 3226.5 5675.0 5099.1 2838.0 1114.1 337.7 84.3 18.2 3.5 0.64.5 0.0 0.0 6.0 196.1 1354.3 3288.5 3857.5 2685.5 1275.2 455.1 130.9 31.9 6.9 1.35.5 0.0 0.0 1.0 51.0 498.4 1602.9 2372.7 2008.3 1126.0 463.6 150.9 41.0 9.7 2.16.5 0.0 0.0 0.2 12.6 167.0 690.3 1257.9 1268.6 825.9 386.8 140.8 42.2 10.9 2.57.5 0.0 0.0 0.0 3.0 52.1 270.1 594.4 703.2 524.9 276.7 111.7 36.7 10.2 2.58.5 0.0 0.0 0.0 0.7 15.4 97.9 255.9 350.6 296.9 174.6 77.6 27.7 8.4 2.29.5 0.0 0.0 0.0 0.2 4.3 33.2 101.9 159.9 152.2 99.2 48.3 18.7 6.1 1.7
10.5 0.0 0.0 0.0 0.0 1.2 10.7 37.9 67.5 71.7 51.5 27.3 11.4 4.0 1.211.5 0.0 0.0 0.0 0.0 0.3 3.3 13.3 26.6 31.4 24.7 14.2 6.4 2.4 0.712.5 0.0 0.0 0.0 0.0 0.1 1.0 4.4 9.9 12.8 11.0 6.8 3.3 1.3 0.413.5 0.0 0.0 0.0 0.0 0.0 0.3 1.4 3.5 5.0 4.6 3.1 1.6 0.7 0.214.5 0.0 0.0 0.0 0.0 0.0 0.1 0.4 1.2 1.8 1.8 1.3 0.7 0.3 0.115.5 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.4 0.6 0.7 0.5 0.3 0.1 0.116.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.2 0.2 0.2 0.1 0.1 0.0
Tz (sec)
-
6SHIP MOTIONS in WAVES
Frequency Domain or Nonlinear Analysis:
Hull Form
3D Panel Code: PRECAL
Motion and ACCL RAOs at 33 freqs and 17 headings
Ship Speed: 75% of design speed-20 -10 0 10 20
0
5
10
15
20
25
-
7LNG Sloshing Analysis by Critical Sloshing Domain Approach
Roll RAO T. ACCL RAO
Encountering period
Contour Map of Sloshing Pressure
Critical Sloshing Load at 70% FLVL,
EW at 70% FLVL|Encountering period Tank resonance period|
< 30% of Tank resonance Period
RAO of DLPs (Roll, Pitch, TACC, LACC)
> 50% of Max RAO
About 20+ sea conditions for each filling level
-
8SLOFE Features
Stream function-based model
Finite-element method
LNG tank w/o internal members
Impact-capturing scheme in low-filling
Validated w/ model test results t/T= 7.8855, Pmax=6.6
Sloshing Simulation
-
9SLOFE: Comparison w/ Experiment (15%H)
-
10
High Filling Level vs. Low Filling Level
Incident angle is less than 4 degree.
Gas pocket can be found before impact.
High-Filling Level:
Standing Wave
Low-Filling Level:
Progressive Wave
Incident angle is greater than 10 degree.
No gas pocket.
-
11
3D Sloshing Impact Simulation
Roll 10 deg., Pitch 5 deg Period 6.64 s
55 60 65 70 75 80 85 90 95 100t (sec)
0
5
10
15
Pre
ssur
e (b
ar)
3D Surge2D Surge
3D Surge
2D Surge
Sway Motion in beam sea Surge Motion in head sea Roll Motion in oblique sea
-
12
Two Phase Flows Simulations for Tank Sloshing
-
13
MARINTEK 138K Partial Filling Model Test
Seakeeping Analysis
Irregular Sloshing Analysis
Critical Wave Condition
Maximum Sloshing Load in the
North Atlantic Waves
Sloshing Model Test
701703
772
716
776 785
756744
747
735 741
784782
710732 702
20
20
TYP.2.5
TY
P. 2.5
TY
P. 5.0
TYP. 5.0
STBD
FWD
Clustered pressure sensors
-
14
Six DOF Sloshing Test Rig & Comparison
-
15
138K Model Test for Partial Filling Study
Check duration to validate Froude scaling
Measured Local Pressure Time History
1:50 scale ModelFroude Scaling for Impact PressureAir & Water at room temperature and atmospheric pressureRigid tank wallNo corrugation3 hr MPEV of impact pressure
Ensemble pressure for clustered pressure sensors (Panel pressure)
ABS Procedure for Data InterpretationValidation
Design load for Impact Strength Assessment
-
16
GTT Model Test for Larbi Ben M'hidi Damage Study
Model Scale Pressure (kPa) Scale Factor
Full Scale Pressure
(kPa)
Froude Scaling 89 33.1 2947GTT Damage Study 89 6.7 600Mach Scaling 89 4.0 352
Scale Law to Full Scale Pressure
Scale law is not unique & full scale value can be significantly different
Different scale law should be applied for different impact type and filling level
Empirical scale law is an averaged scale law for different impact type for high filling conditions and may not be applicable to low filling conditions.
Scale Law for Sloshing Impact Pressure
-
17
Hidden factor of safety & Conservatism
l Ship motion-sloshing interaction
l Cushioning due to corrugation
l Dynamic material properties
l Conservative environmental and loading scenario
-
18
Ship motion Sloshing interaction
l Similar to Anti-roll tank
l Significant effect on roll and accelerations
l Reduction of sloshing pressures
-
19
Large LNGC Analysis:Ship and Tank Size Comparison
138K: 276 (m)
LLNGC: 322 (m)46m longer
LLNGC over 200K : 51 (m)8.4m wider
138K: 42.6 (m)
-
20
Sloshing Analysis for Large LNGC
Maximum Panel Pressure at Corner
0
1
2
3
4
5
6
7
8
70% 80% 90% 95%
Filling Level
P (
bar
) 138K_L43
200K_L51
200K_L55
Sloshing pressure at corners
l 28% increase of sloshing load on insulation box over 138K standard size
l Model test confirmed approximately 30% increase of sloshing pressure
-
21
Dry Drop Tests for Impact Strength
Full-Scale Insulation Model
Impact Duration Controlled by Drop Weight
Impact Magnitude by Drop Height
Failure Mode of Insulation System
Fracture and Crack Propagation
Impact Strength
-
22
Drop Test for Corrugation Effect
-
23
Simplified Strength Assessment Procedure
Sloshing Load
Ship Motion
Model Scale Sloshing Pressure
Full Scale Sloshing Pressure
Cushioning due to corrugation
Strength of Containment System
Static Strength
Impact Strength
Factor of Safety = Impact Strength
Max. Full Scale Sloshing Impact Load
-
24
Advanced Strength Assessment Procedure
Sloshing Analysis/Model TestIdentification of Critical Sloshing
Impact LoadRigid Impact Pressure
Impact Strength TestScheme Validation
Failure ModeImpact Strength
Hydroelastic AnalysisStructural Response
Resultant Impact Pressure
Dynamic Material PropertyVisco-elasticity
Damping
Acceptance Criteria
LoadImpact Resultant StrengthImpactSafetyofFactor =
-
25
Material Property Testing at Low Temperature
-
26
Structure Responses of Containment System
Mark III
NO 96
LNG
Structure
Strikerbar
Incident bar Transmitted barSpecimen
Strain gaugeV0 Embedded quartz loadcell
Strength Assessment at Level 1
Static Stress FE Analysis
Buckling FE Analysis
Strength Assessment at Level 2
Linear Dynamic FE Analysis
Dashpot System Representing LNG Damping
Buckling FE Analysis
Strength Assessment at Level 3
Nonlinear Dynamic FE Analysis
Fluid-Structure Interaction
Visco-elasticity
Dynamic Material Property Test
-
27
Structure Analysis of Containment System for Fluid-Structure Interaction
LNG
Foam
Pressure reduction due to Structural Motion
Stress propagation & dissipation
Stress concentration on mastic
Acoustic wave emission
P U
-
28
Buckling Analysis on NO 96 Containment System
Critical buckling load
-
29
( )( )tptp
FactorLoadelasticHydrorigidt
flext
max
max-
Hydro-elastic Effect on NO 96 Containment System
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.000 0.002 0.004 0.006 0.008 0.010 0.012 0.014 0.016
Duration [s]
Hyd
ro-e
last
ic L
oad
Fac
tor
Sigma=0.2Sigma=1.0Sigma=1.8
-
30
Guidance Notes for Strength Assessment of Membrane-Type LNG Containment System
l Objective is to provide evaluation procedure and criteria based on sloshing analysis, model test and structure analysis of containment system
l Both new novel design and conventional design are considered
l Standard filling condition and any partial filling conditions are addressed
l Interaction between LNG liquid and structure and dynamic behavior of containment system are considered using advanced analysis techniques
l Three different levels of structure analysis, static, simplified dynamic and non-linear dynamic structure analysis are offered.
-
31
Adt
dUCDUUC
dzdF
md r+r= 21
Morrison equation for sectional force
Time-domain simulation of sloshing
Structural analysis
NASTRAN, SACS, API Code
SLOFE for Sloshing & Load by
Long-term prediction of Ship motion
Design life in the North Atlantic Waves
Pump Tower Analysis
Liquid Dome Cover
Base Plate
Pump TowerMain Section
-
32
Pump Tower Structure
Top-Details
Discharge Pipe
Emergency Pipe
Bottom-Details
Standard Strut
Filling Pipe
Base Plate
-
33
Drag phase
Inertial phase
Pump Tower Load at low filling level (25%H)
40 44 48time (sec)
-4E+005
-2E+005
0E+000
2E+005
4E+005F
orce
(N
)
Force on membe r 1Total forceInertia forceDrag force
-20 -15 -10 -5 0 5 10 15 20Velocity (m/s)
0
0.2
0.4
0.6
0.8
1
Rel
ativ
e he
ight
-150 -100 -50 0 50 100 150Accele ration (m/s2)
-1E+005 -5E+004 0E+000 5E+004 1E+005Sectional Force (N/m)
VelocityAccelerationSectional force
-20 -15 -10 - 5 0 5 10 15 20Velocity (m/s)
0
0.2
0.4
0.6
0.8
1
Rel
ativ
e he
ight
-150 -100 -50 0 50 100 150Acceleration (m/s2)
-1E+005 -5E+004 0E+000 5E+004 1E+005Sectional Force (N/m)
Velocity
AccelerationSectional force
-
34
Loads & Responses of Pump Tower
l Sloshing Loads on Pump Tower
l Gravitational Load due to Pitch and Roll Motion and Self-Weight
l Inertial Load
l Thermal load
-
35
API Code Checking- Brace Members & Connections in Partial Filling: Example Analysis
Combined Axial Compression and Bending - Unity CheckCombined Axial Compression and Bending - Unity Check
Element 61Element 61Element 61
Element 62Element 62Element 62
Element 89Element 89Element 89
Element AxialStress/Allowable
(kgf/cm2)
In Plane BendingStress /Allowable
(kgf/cm2)
Out-of-Plane BendingStress/Allowable
(kgf/cm2)
Max CombUnityCheck
61 -1013/855 -534/1301 125/1301 1.8462 1072/1040 -306/1301 47/1301 1.26989 -624/1040 174/1301 3.0/1301 1.016
Design change for reinforcement may be required for partial filling condition
-
36
Vibration of pump tower structure
l Natural Frequencies and Mode shapes
l Resonance check by comparison between natural frequency and exciting frequencies of hull girder vibration and engine vibration
l Forced vibration and acceptance criteria
-
37
Spectral Fatigue Analysis or Simplified Fatigue Analysis
Fatigue Damage during Lifetime Service Period
Weibull Parameter
SN CurveStress Range at Reference Prob. Level
Fatigue Loads due to Sloshing
-
38
Pump Tower Base Support FE Analysis
-
39
Stress Distribution of Mastic
-
40
Stresses on Densified Plywood
-
41
FE Analysis on Hull Structure with Mark III Containment System under Ice Loads
-
42
Mark III Containment System
Hull Structure with Mark III Containment System
-
43
Recommendations for further study
l Corrugation effect on sloshing
l Fluid & gas interaction in CFD simulation
l Ship motion and sloshing coupling effect
l Full scale measurement for scale law
l Vibration effect on containment system
l Membrane fatigue
l Harsh wave environment analysis
l Containment system for Arctic operation
l Ship to ship and ship to terminal cargo transfer
-
44
The End of Presentation
&
Questions & Answers