1
CeSOS HighlightsTrondheim 27-29 May 2013
CM Larsen:Slendernstructuresand VIV
Riser technologyLong term aim: Improve modelling capabilities in
RIFLEX in order to make the program more useful for analysis of deep
d water systems and marine operations
2
Heave compensators; frequent damages
Heave compensation:Ideal model: Integrated hydraulic system and structural dynamics model:
Simulation modelof hydraulic systemas a part of a non-linearFE code for marine riser analysisanalysis
PhD candidate Ausberto Medina
3
Dynamics of flexible pipes from non-stationary (slug) flow
Riser dynamics Multi-phase flow:Riser dynamics p fTime varying geometryprof. Ole Jørgen Nydal
Direct data communicationHLA / DLL / Total integration
PhD candidate Arturo Ortega
Communication between two independent computer programs:High Level Architecture
4
Snapshots of flexible riser with slug flow
PhD: Anne Martine RustadCollision between parallel tensioned risers in current
Conventionaltension control:Constant tension,gives different setdown andcollision
Current
Alternativetension control 1:Equal payoutgives different tension which helps, but collision
ill
Alternativetension control 2:Equal effective length (payout + actual riser length)
Carl M. Larsen: Slender structures at DNV, May 2008
collision betweenupstream anddownstream risermay occur
may still take place since different tension will give different length
length)gives parallel risers that do not collide
5
Steel catenary risers –effective tension and sagbend moment
Bending moment and effective axial forceclose to TDP is strongly influencedby downward axial velocity at upper endby downward axial velocity at upper end
Post doc Elizabeth Passano
Results from non-linear simulations
Corresponding indiv. maxima of ff i i
1400500 m,16.5 m, 16.5 s
14.5 m, 16.0 s
effective tension and bending moment close to TDP, and axial velocity for 500 m depth (grey) and 1800 m depth (coloured) 200
400
600
800
1000
1200
ensi
on (
kN
), m
ax. b
end
ing
mom
ent
(kN
m)
,12.0 m, 15.5 s
1800 m,16.5 m, 16.5 s14.5 m, 16.0 s12.0 m, 15.5 s
Bending moment (kN m)
depth (coloured)
-400
-200
0
-2.5-2-1.5-1-0.5 0
Min
. eff
. t
Min. axial velocity (m/s)Axial velocity (m/s)
Effective axial force (kN)
6
1200
1400
t (k
Nm
)
16.5 m, 16.5 s14.5 m, 16.0 s12 0 m 15 5 s
Results from non-linear simulations
0
200
400
600
800
1000
ensi
on (
kN
), m
ax. b
end
ing
mom
ent
Max. bending moment
-1.5
8 m
/s
12.0 m, 15.5 sFit
1800 m waterdepth, varyingsignificant wave height and peakperiode
-400
-200
-2.5 -2 -1.5 -1 -0.5 0
Min
. eff
. te
Min. axial velocity (m/s)
Min. effective tension
periode
Est. distEst sample
Sample: 12.0 mSample: 14.5 m
Data from one simulation used to find a functional relation between axial veloccity and response
0.9999
0.9990
0.9900
0.9000
0.5000
0.1000
Pro
bab
ilit
y
Eff. tension Bending moment
pSample: 16.5 m
-200 0 200 400 600 800 1000 1200
Eff. tension (kN), bending. moment (kNm)
Simulated maxima / minima samples for significant wave height 12.0 (blue), 14.5 (light blue) and 16.5 m (red), estimated maxima / minima samples (black) and estimated maxima / minima distributions (grey).
7
Have we done everything? NO!New techniques for scaled models of deep water floaters
Today's laboratory:D=10m, scale 1:40;400 m water depth
10 m
50 m
400 m water depth
2000 m will requirelaboratory with 50 mwater depth
Alternative method for model tests
Passive springs
Real time computation of forses in slender structures from
Passive springsto obtain correcteigenfrequencies for in-plane motions
structures from measured motions; represent restoring and damping from deep water anchor lines and risers
Forces are adjusted to include dynamics form risers and mooring lines
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VIVV VVortex Induced VibrationsLong term aim: Improve empirical analysis tools VIVANA
by developing new experimental techniques and new ways of using data from experiments
Key fetures: Self-limiting, but not a nice, stable responseeven under stationary conditions
Use of supression devices:
9
We had a workshop 20 years ago
currentprofile
currentprofile
- large differences between results fromcomputer programs
Results 10 years ago
10
How can VIV be calculated?
• Computational fluid dynamics (CFD)
• Empirical models; based on– data from free oscillation tests
d t f f d ill ti t t
colorful fluid dynamics
– data from forced oscillation tests– data from oscillating flexible beams
• Improvements from CeSOS research
Aronsen's PhD: IL coefficientsForced motion tests
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Dynamic IL excitation coefficient and added mass
0 sin( )IL
FC
1st
, 20.5e ILCDLU
21
0, 2 2
0
cos( )
0.25a IL
FC
D L x
3D CFD on VIV
0,25
00.95.6
0.3
1 0
1,5
Present Arosen (2007)
Comparison between CFD and experimentsIn-line forced motions in current (PhD candidate Aronsen)Post doc. Z. Huang
0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9
0,05
0,10
0,15
0,20
1.02
1.02
1.02
1.02
1.02
1.0
1.0
1.0
1.0
0
0.95
0.95
0
0.9
0.9
0.9
0.9
0.8
0.6
0.8
0.8
0.6
0.6
0.
0.3
0.3
0
0
Am
plit
ud
e r
atio
(A
/D)
Nondimensional frequency
0,2 0,3 0,4 0,5 0,6 0,7 0,8-1,0
-0,5
0,0
0,5
1,0
Ad
ded
mas
s C
a
Nondimensional frequency
Figure 5. Comparison between the numerical results and experimental contour plot of the added mass. The thick line indicates the two excitation regions. ▪, present results.
12
Kristoffer Aronsen’s PhD:Systematic variation of phase & amplitude
Flowdirection→ →
←← →
510
45
77 90
0.2
0.4
0.6
0.8
1
0.6
0.8
1
[−]
0 45 90 180 225 270
Phase angle, α
→→ →
←←
←
→
→
Carl M. Larsen: Slender structures at DNV, May 2008
05
180185190
225
250 264 0.1 0.15 0.2 0.25 0.30
0.2
0.4
0.6
A/D
[−
Nondimensional frequency [−]
IL and CF forced motions:All data from 300 tests, AIL=0.5 ACF
Hydrodynamic coefficients for combined CF and IL oscillations, all cases
15
Cd
0
5
10
Co
eff
icie
nt
Cd
Ce,cf
Ca,cf
Ce,il
Ca,il
-10
-5
0 0.2 0.4 0.6 0.8 1 1.2
Response amplitude A/D
13
Data for same phase and relative CF/IL amplitude, varying frequency and A/D
Coefficients for alfa=77, (IL/CF)=0.5
8
-2
0
2
4
6
8
Co
effi
cien
ts (
-)
Ce,cf
Ca,cf
Ce,il
Ca,il
-8
-6
-4
0 0.2 0.4 0.6 0.8 1 1.2
A/D_CF (-)
C
(A/D)CF
Realistic curve, CF oscillation only
All parameters except for amplitude constant
Combined CF and IL oscillation, hydrodyn. coefficientsf_hat = 0.147; A_IL = 0.5 A_CF; phase = 77 deg.
5Ce cf
0
1
2
3
4
n-d
im.
coef
fici
ent
Ce,cfCa,cfCe,il
Ca,ilCd
-3
-2
-1
0 0.2 0.4 0.6 0.8 1 1.2
CF oscillation amplitude (A/D)
No
n
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VIVANA: Linear FD analysisAnalysis procedure for structures with local non-linear effects: Kamran Koushan PhD
• Non-linear static analysis• Conventional VIV analysis in frequency domain• Added mass, damping and excitation forces
found• These data are used in a non linear time • These data are used in a non-linear time
domain analysis• NOTE: Only local effects; global response
must be close to the initial response estimate
OMAE 2004
10.0
15.0
20.0
tres
s rm
s (M
Pa)
Linear analysis
Non-linear analysis
Free spanning pipelineNonlinear contact betweenpipe and sea bottom at theshoulders will reduce stresses
0.06
0.08
0.10
nt (
m)
0.02
0.03
0.04
t (m
)
0.0
5.0
0 50 100 150 200 250 300 350 400
Tota
l st
Pipe coordinate (m)
compared to linear analysis
-0.06
-0.04
-0.02
0.00
0.02
0.04
116 120 124 128 132
Pipe coordinate (m)
Dyn
am
ic d
ispl
ace
men
-0.04
-0.03
-0.02
-0.01
0.00
0.01
116 120 124 128 132
Pipe coordinates (m)
Dyn
amic
dis
plac
emen
15
Database for hydrodynamic coefficients, combined IL and CF response?
o 4 independent variables harmonic IL and CFo 4 independent variables, harmonic IL and CF
o Resolution of 20 values for each variableo 160 000 tests neededo Possible by use of an automatic lab?
o 10 minutes between each runo Takes 3 years!
phasefD
A
D
A
ILCF
ˆ
IL
CF
o Takes 3 years!o 15 values for each parameter requires one yearo But will that be useful?o What about higher order components?
New test technique:Cross section orbits for a flexible beam measured, later used as forced motions for rigid cylinder. Forces measured for the same non-dimensional parameters
10.05 m
10.50
Figure 3: Experimental set-upMeasured forces will include higher order components
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Three sets of experiments
Prashant Soni: Uniform flow moderate mode orders tension Uniform flow, moderate mode orders, tension dominated pipe
Ida Aglen:Use of Ormen Lange test data, low mode orders, bending stiffness dominated pipe
Decao Yin: NDP highe mode order tests, mostly tension dominated
Ida Aglen The winner of the first «Researcher Grand Prix»
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Prashant Soni (PhD 2008)i:
Results from 250 individual tests,all orbits from uniform flow cases
8
10
CeCF, 1ωCaCF 1ω
0
2
4
6
8
VIV
co
effi
cien
ts (
-)
CaCF, 1ωCeIL, 2ωCaIL, 2ω
Trends?-4
-2
0.125 0.138 0.150 0.163 0.175 0.188 0.200
Non-dimensional frequency (-)
Alternative approach:
Find coefficients directly from flexible beam experiments Jie Wu, PhD
Measure responseMeasure response(strains, accelerations, displacements)
Calculate forces by inverse analysis!y
Supported by Philippe Mainçon
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System identification:
Normally we solve a dynamic responseproblem by calculating response from given loadsproblem by calculating response from given loads
Unknown response Knownforces
Question: If we have measured the responseQuestion: If we have measured the response,can we find the forces that must have been there?
Answer: Well, yes – it is possible, but not asstraightforward as you might believe
Displ. std
80
90
100
New set of curves found from these (and other) results
Excitation Coefficient Database
0 6
0,7
0,8 0
10
20
30
40
50
60
70
80
0 0,002 0,004 0,006 0,008 0,01 0,012 0,014
Displ. (m)
Le
ng
th (
m)
Ce_v1
Displ. modal
Ce_gopal
-0,1
0
0,1
0,2
0,3
0,4
0,5
0,6
0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4
Non-dimensional freq. f_h
Am
pli
tud
e R
atio
A/D
acl0
aclmax
clmax
cla0
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Verification 1: Bearman & Chaplin
Spring to limit force variation force variation during a test
Force measurementto control tension
37
to control tensionvariation during a test
Extended comparison:All cases, and both IL and CF response: Dominating mode (frequency) and amplitude show same trends in experiments and calculations
0.3
0.4
0.5
sig/d
ExperimentsVIVANA
0.08
0.1
0.12
0.14
0.16
sig/d
ExperimentsVIVANA
0
0.1
0.2
0 10 20 30 40 50
Red. velocity
0
0.02
0.04
0.06
0 10 20 30 40 50
Red. velocity
20
0.6
0.8
1
1.2
1.4
A/D
[-]
Series 10
Pure ILCF
IL w/ CFExperiment, CFExperiment, IL
Verification 2:Ormen Lange free spanning pipeline study;CF and IL mode
2.5
3
Series 10
Pure ILCF
IL w/ CFExperiment, CFExperiment, IL
5
6
Series 10
Pure ILCF
IL w/ CFExperiment, CFExperiment IL
0
0.2
0.4
0 0.05 0.1 0.15 0.2 0.25
Current [m/s]
CF and IL mode, frequency and amplitude
0
0.5
1
1.5
2
0 0.05 0.1 0.15 0.2 0.25
Fre
q. [H
z]
Current [m/s]
Experiment, IL
0
1
2
3
4
0 0.05 0.1 0.15 0.2 0.25
Mod
e
Current [m/s]
Experiment, IL
Frequency concert:Concurrent and consecutive response frequencies will have different excitation zones
Combination of frequencies:Concurrent response frequencies, (space sharing)Frequencies act simultaneously, no overlap between excitation zones
min max
Excitationzone for theprimary response frequency; secondeigenfrequency
UC
ˆ 0
c
f Df =
U
5
Mode 3
Combination of frequencies:Consecutive response frequencies, (time sharing )Shift of frequency, full excitation zone when active
5
UC 0ˆc
f Df
Umin max
Excitation zones for each possibleresponse frequency
12
3
4
0.125 0.3
5
Mode 1
5
12
3
4
0.125 0.3
Space sharing vs. Time sharing
21
Concurrent or consecutive response frequencies:Concurrent will in most cases with shear currentgive more fatigue damage than consecutive
0.08
0.1
0.12
0.14
0.16
0.18
(m)
Response standard deviations
ConcurrentConsecutive
3
4
5
6
7
8
(MPa
)
Srtess standard deviations
ConcurrentConsecutive
g f g g
Response amplitudes Stress std. dev.
0
0.02
0.04
0.06
0 100 200 300 400 500 600 700
Arc length (m)
0
1
2
3
0 100 200 300 400 500 600 700
Arc length (m)
Red: Time sharing Blue: Space sharing
Illustration of the ”frequency concert”in time and space: Both concurrent and consecutive assumptionsrepresent simplifications!
Positi
Freque
Time
ion
ency
22
One step further:
Philippe Mainçon: Find forces from recent trajectory
L i hiLatest time historyof relative velocitydefines the force!
uIL
FIL(t*), FCF(t*)uCF
TIME DOMAIN VIV MODELING
At each cross sectionapproximate each component of the relative velocityyas a linear combination of n = "15" Laguerre polynomials
Method ensures fine descriptio of recent past, coarse description of further past
0.5
1
1.5x 10
4
y [R
e]
Very fast computation…
0 0.5 1 1.5 2 2.5
x 104
-1.5
-1
-0.5
0
x-velocity [Re]
y-ve
loci
ty
23
Promising results so far!
What is the potential?• Integrated CF and IL response in time domain!• Higher order force and response components
directly pesent!
• But: We are at present far from a general model
• Need a large data base of trajectories• Data based on our forced motion tests with
measured trajectories is available
Thank you for your y yattention!
Reference list, Slender marine structures; Carl M. Larsen PhD thesis – Kjetil Skaugset (2003): On suppression of VIV of circular cylinders by radial water jets – Kristoffer Aronsen (2007): An experimental investigation of IL and combined IL-CF VIV – Anne Marthine Rustad (2007): Modeling and control of top tensioned risers – Prashant Soni (2008): Hydrodynamic coefficients for VIV of flexible beams – Jie EWu (2011): Hydrodynamic force identification from stochastic VIV experiments with slender beams – Decao Yin (2013): Experimental and numerical analysis of combined IL and CF VIV
Journal papers /1/ Skaugset, K.B. and Larsen, C.M.:”DNS and experimental investigation on vortex shedding and VIV
modification using radial water jets along circular cylinders”, Journal of Fluid and Structures (Paper accepted for publication 2004)
/2/ Leira, B.J., Sørensen, A.J. and Larsen, C.M.: “A reliability-based control algorithm for dynamic positioning of floating vessels”. Journal of Structural Safety, Vol 26, 2004, pp 1-28
/3/ J R Chaplin, P W Bearman, Y. Cheng, E Fontaine, J.M.R. Graham, K Herfjord, F.J. Huarte, M Isherwood, K. Lambrakos, C M Larsen, J R Meneghini, G Moe, R.J. Pattenden, M S Triantafyllou, R.H.J. Willden: "Blind predictions of laboratory measurements of vortex-induced vibrations of a Tension Riser". Journal of fluid and structures 21 (2005), 25-40
/4/ Baarholm, Gro S., Larsen, C.M. and Lie, Halvor: "On fatigue damage accumulation from in-line and cross-flow vortex induced vibrations on risers" Journal of Fluids and Structures, 22 (2006) 109-127
/5/ Baarholm, Gro S., Larsen, Carl M. and Lie, Halvor: "Reduction of VIV using suppression devices – A Theoretical Approach" Journal of Marine Structures 2006 /6/ Rustad, A. M., Larsen, C. M. and Sørensen, A. J. FEM modelling and automatic control for collision
prevention of top tensioned risers. Marine Structures, 2008, Vol. 21, No. 1, pp. 80-112. /7/ Huang, Z. Y. and Larsen, C. M. Large eddy simulation on interaction between in‐line and crow‐flow
oscillation of a circular cylinder China Ocean Engineering 24(4)
Invited key note lectures /1/ Larsen, C. M. and Lie, H.: On Hydrodynamic Coefficients for Combined Cross-Flow and In-Line Vortex
Induced Vibrations. 27th International Conference of Offshore Mechanics and Arctic Engineering, OMAE 200857569, 15 p., 2008, 15-20 June, Estoril, Portugal.
/2/ Larsen, C. M.: Slender marine structures - key features and methods for design analysis. The 1st International Conference on Sustainable Infrastructure and Built Environment (SIBE), 2009, 2-3 Nov. - Bandung, Indonesia.
/3/ Larsen, C.M., Passano, E. and Lie, H.: Recent development of the empirical basis for prediction of vortex induced vibrations, The 2nd International Conference on Sustainable Infrastructure and Built Environment (SIBE), 2012, 12-13 Nov. - Bandung, Indonesia.
Conference papers /1/ Skaugset, K. and Larsen, C.M.: “Drag force reduction and VIV suppression of circular cylinders using
radial water jets”, OMAE2003-37102, , 22nd International Conference on Offshore Mechanics and Arctic Engineering, June 2003, Cancun, Mexico
/2/ Yttervik, R., Reinholdtsen, S-S, Larsen, C.M. and Furnes, G.K.: ”Marine operations in deep water and a variable current flow environment”. 3rd International Conference on Hydroelasticity in Marine Technology, September 2003, Oxford, UK
/3/ Larsen, Carl M., Baarholm, Gro S., Passano, Elizabeth and Koushan, Kamran: "Non-Linear Time Domain Analysis of Vortex Induced Vibrations for Free Spanning Pipelines" [OMAE2004-51404] Proceedings of 23rd International Conference on Offshore Mechanics and Arctic Engineering, Vancouver, Canada, June 2004
/4/ Soni, P. and Larsen, C. M. "Dynamic Interaction Between Spans in a Multi Span Pipeline Subjected to Vortex Induced Vibrations", OMAE2005-67192, 24th International Conference on Offshore Mechanics and Arctic Engineering, 12-17 June 2005, Halkidiki, Greece
/5/ Larsen, C.M., Baarholm, G.S. and Lie, H: "Influence From Helical Strakes on Vortex Induced Vibrations and Static Deflection of Drilling Risers" OMAE2005-67192. 24th International Conference on Offshore Mechanics and Arctic Engineering, 12-17 June 2005, Halkidiki, Greece
/6/ Aronsen, K:, Larsen, C.M. and Mørk, K.: " Hydrodynamic Coefficients From In-Line VIV Experiments" OMAE2005-67393, OMAE2005-67192. 24th International Conference on Offshore Mechanics and Arctic Engineering, 12-17 June 2005, Halkidiki, Greece
/7/ Larsen, C.M. and Koushan, K.: " Empirical model for the analysis of vortex induced vibrations of free spanning pipelines" Eurodyn, Paris 2005
/8/ Larsen, C.M. and Passano, E.: "Time and frequency domain analysis of catenary risers subjected to vortex induced vibrations" OMAE 2006-92149, Hamburg
/9/ Passano, E. and Larsen, C.M.: "Efficient analysis of a catenary riser" OMAE 2006-92308, Hamburg /10/ Baarholm, G.S., Larsen, C.M. and Lie, H.: "Effect of strakes on fatigue damage due to cross-flow VIV"
3rd International conference on hydroelastisity in marine technology, Wuxi 2006 /11/ Lie, H. and Larsen, C.M.: "Vortex induced vibrations of deepwater risers and pipelines - review of model
test results" 3rd International conference on hydroelastisity in marine technology, Wuxi 2006 /12/ Soni, P.K. and Larsen, C.M.: "An experimental investigation of interaction between adjacent spans in
pipelines" 3rd International conference on hydroelastisity in marine technology, Wuxi 2006 /13/ Rustad, A. M., C. M. Larsen and A. J. Sørensen (2007). Deep Water Riser Collision Avoidance by
Top Tension Control. In Proc. OMAE, 26th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2007-29172, June 10-15, San Diego, California, USA.
/14/ Rustad, A. M., A. J. Sørensen and C. M. Larsen (2007). Supervisory Switched Control of Marine Risers. In Proceedings of the 7th IFAC Conference on Control Applications in Marine Systems (CAMS2007), September 19-21, Bol, Croatia.
/15/ Anne M. Rustad, Carl M. Larsen, Asgeir J. Sorensen Deep Water Riser Collision Avoidance by Top Tension Control. PAPER: OMAE2007-29172 /16/ Ioannis K. Chatjigeorgiou, Elizabeth Passano, Carl M. Larsen Extreme Bending Moments on Long Catenary Risers Due to Heave Excitation, PAPER: OMAE2007-29384 /17/ Elizabeth Passano; Carl M. Larsen Estimating Distributions for Extreme Response of a Catenary Riser. PAPER: OMAE2007-29547 /18/ Jie Wu, Carl M. Larsen Hydrodynamic Force Identification From Vortex Induced Vibration Experiments With Slender Beams. PAPER: OMAE2007-29174 /19/ Prashant K. Soni, Carl M. Larsen, Chittiappa Muthanna Vortex Induced Vibration of a Rigid Cylinder Oscillating With a Given Trajectory Profile, PAPER: OMAE2007-29193 /20/ Djoni E. Sidarta, Kostas F. Lambrakos; Carl M. Larsen Hydrodynamic Coefficients for Riser In-Line VIV in Sheared Currents. PAPER: OMAE2007-29519 /21/ Kristoffer H. Aronsen; Carl Martin Larsen Hydrodynamic Coefficients for In-Line Vortex Induced Vibrations, PAPER: OMAE2007-29531 /22/ Carl M. Larsen; Rune Yttervik; Kristoffer Aronsen Calculation of In-Line Vortex Induced Vibrations of Free Spanning Pipelines, PAPER: OMAE2007-29533 /23/ Lie, H., Larsen, C. M. and Kaasen, K. E. Frequency domain model for prediction of stochastic vortex
induced vibrations for deep water risers. Proceedings of the 27th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2008-57566, 2008, 15-20 June - Estoril, Portugal.
/24/ Rustad, A. M. and Larsen, C. M. Collision prevention of two different top tensioned risers by automatic control. Proceedings of the 27th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2008-57496, 2008, 15-20 June - Estoril, Portugal.
/25/ Soni, P. K. and Larsen, C. M. Investigating the relevance of strip-theory for pipelines subjected to vortex-induced vibrations. Proceedings of the 27th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2008-57551, 2008, 15-20 June - Estoril, Portugal.
/56/ Swithenbank, S. and Larsen, C. M. The importance of mode number on in-line amplitude of vortex-induced vibrations of flexible cylinders. Proceedings of the 27th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2008-57531, 2008, 15-20 June - Estoril, Portugal.
/27/ Swithenbank, S., Larsen, C. M., Vandiver, J. K. and Lie, H. Reynolds number dependence of flexible VIV response data. Proceedings of the 27th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2008-57045, 2008, 15-20 June - Estoril, Portugal.
/28/ Wu, J., Larsen, C. M. and Kaasen, K. E. A new approach for identification of forces on slender beams subjected to vortex-induced vibrations. Proceedings of the 27th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2008-57550, 2008, 15-20 June - Estoril, Portugal.
/29/ Mainçon, P., Barnardo, C. and Larsen, C.M. (2008): “VIV force estimation using inverse FEM”, OMAE 2008-57375, Estoril, Portugal
/30/ Larsen, C.M. and Lie, H. (2008) “On hydrodynamic coefficients for combined cross-flow and in-line vortex indiced vibrations”, OMAE 2008-57569, Estoril, Portugal
/31/ Aglen, I., Larsen, C. M. and Nielsen, F. G. Characterization of Measured VIV for Free Spanning Pipelines. OMAE2009, Proceedings of the 28th International Conference on Ocean, Offshore and Arctic Engineering. OMAE2009-79561, 2009, May 31-June 5 - Honolulu (HA), USA.
/32/ Huang, Z. Y., Larsen, C. M. and Cui, W.C. 3-D LES study on a forced oscillating circular cylinder following the figure of eight movement. Proceedings of the Conference on Hydroelasticity in Marine Technology, 2009, 8-10 Sept. - Southampton, UK.
/33/ Soni, P. K. and Larsen, C. M. Vortex Pattern Comparison for Periodic and Harmonic Combined Cross-Flow & In-Line Forced Oscillations. OMAE2009, Proceedings of the 28th International Conference on Ocean, Offshore and Arctic Engineering. OMAE2009-80089, 2009, May 31-June 5 - Honolulu (HA), USA
/34/ Soni, P. K., Larsen, C. M. and Wu, J. Hydrodynamic Coefficients for Vortex Induced Vibrations on Slender Beams. OMAE2009, Proceedings of the 28th International Conference on Ocean, Offshore and Arctic Engineering. OMAE2009-79797, 2009, May 31-June 5 - Honolulu (HA), USA.
/35/ Szwalek, J. and Larsen, C. M. Reynolds Number Effects on Hydrodynamic Coefficients for Pure In-Line and Pure Cross-Flow Vortex Induced Vibrations. OMAE2009, Proceedings of the 28th International Conference on Ocean, Offshore and Arctic Engineering. OMAE2009-79399, 2009, May 31-June 5 - Honolulu (HA), USA.
/36/ Wu, J., Larsen, C. M., Lie, H., Passano, E. and Kendon, T. E. Prediction of Fatigue Damage from Stochastic Vortex Induced Vibrations. Proceedings of the Conference on Hydroelasticity in Marine Technology, 2009, 8-10 Sept. - Southampton, UK..
/37/ Wu, J., Mainçon, P., Larsen, C. M. and Lie, H. VIV Force Identification Using Classical Optimal Control Algorithm. OMAE2009, Proceedings of the 28th International Conference on Ocean, Offshore and Arctic Engineering. OMAE2009-79568, 2009, May 31-June 5 - Honolulu (HA), USA.
/38/ Huang, Z. Y., and Larsen, C. M. A Numerical Study on Vortex Induced Forces and Wake Structures of an Oscillating Cylinder. BBVIV-6. The 6th IUTAM Symposium on Bluff Body Wakes and Vortex-Induced Vibrations. June 22-25, 2010, Capri Island, Italy.
/39/ Larsen, C.M., Aronsen, K. and Soni, P.: "On empirical models for higher order frequency components of vortex induced vibrations", BBVIV-6. The 6th IUTAM Symposium on Bluff Body Wakes and Vortex-Induced Vibrations. June 22-25, 2010, Capri Island, Italy.
/40/ Huang, Z., and Larsen, C. M. Large Eddy Simulation of an Oscillating Cylinder Close to a Wall Proceedings of the 29th International Conference on Ocean, Offshore and Arctic Engineering June 6-11, 2010. Shanghai, China. OMAE2010-20006
/41/ Larsen, C. M., Wu, J., and Lie, H.: On the Understanding of Non-Stationary VIV of Slender Beams. Proceedings of the 29th International Conference on Ocean, Offshore and Arctic Engineering June 6-11, 2010. Shanghai, China. OMAE2010-20348
/42/ Passano, E., Larsen, C. M. and Wu, J. VIV of free spanning pipelines: Comparison of response from a semi-empirical code to model tests Proceedings of the 29th International Conference on Ocean, Offshore and Arctic Engineering June 6-11, 2010. Shanghai, China OMAE 2010-20330
/43/ Soni, P.K. and Larsen, C. M. Response of pipelines under VIV, an experimental investigation Proceedings of the 29th International Conference on Ocean, Offshore and Arctic Engineering June 6-11, 2010. Shanghai, China. OMAE2010-20675
/44/ Sten, R., Hansen, M.R., Saevik, S. and Larsen, C. M. Force Variations in Heave Compensating System for Ultra Deep Water Drilling Risers Proceedings of the 29th International Conference on Ocean, Offshore and Arctic Engineering June 6-11, 2010. Shanghai, China OMAE 2010-20011
/45/ Wu, J. Larsen, C. M. and Lie, H. Estimation of Hydrodynamic Coefficients for VIV of Slender Beam at High Mode Orders Proceedings of the 29th International Conference on Ocean, Offshore and Arctic Engineering June 6-11, 2010. Shanghai, China OMAE 2010-20327
/46/ Yin, D. and Larsen, C. M.: On Determination of VIV coefficients under shear flow condition, Proceedings of the 29th International Conference on Offshore Mechanics and Arctic Engineering. (OMAE 2010-20306). 6-11 June 2010, Shanghai, China.
/47/ Aglen, I.M. and Larsen, C.M.: Importance of Added Mass for the Interaction between IL and CF Vibrations of Free Spanning Pipelines (OMAE2011-49966). Proceedings of the 30th International Conference on Ocean, Offshore and Arctic Engineering. June 19-24, 2011 - Rotterdam, The Netherlands.
/48/ Huang, Z. and Larsen, C. M.: Numerical Simulation on Vortex-Induced Vibration of an Elastically Mounted Circular Cylinder with Two Degrees of Freedom (OMAE2011-49573). Proceedings of the 30th International Conference on Ocean, Offshore and Arctic Engineering, June 19-24, 2011 - Rotterdam, The Netherlands
/49/ Mainçon, P. and Larsen, C. M.: Towards a Time-Domain Finite Element Analysis of Vortex Induced Vibrations (OMAE2011-49539). Proceedings of the 30th International Conference on Ocean, Offshore and Arctic Engineering, June 19-24, 2011 - Rotterdam, The Netherlands.
/50/ Yin, D. and Larsen, C. M.: Experimental and Numerical Analysis of Forced Motion of a Circular Cylinder (OMAE2011-49438). Proceedings of the 30th International Conference on Ocean, Offshore and Arctic Engineering, June 19-24, 2011 - Rotterdam, Netherlands
/51/ Larsen, C.M., Zhao, Z. and Lie, H. (2012): “Frequency components of vortex induced vibrations in sheared current”, OMAE2012-83092, Rio de Janeiro, Brazil
/52/ Yin, D. and Larsen, C.M. (2012): “Forced motion experiments with measured motions from flexible beam tests under uniform and sheared flows”, OMAE2012-83160, Rio de Janeiro, Brazil
/53/ Passano, E., Larsen, C.M. and Lie, H. (2012): “Comparison of calculated in-line vortex induced vibrations to model tests”, OMAE2012-83387, Rio de Janeiro, Brazil
/54/ Ortega, A., Rivera, A., Nydal, O.J. and Larsen, C.M.: On the Dynamic Response of Flexible Risers Caused by Internal Slug Flow (OMAE2012-83316). Proceedings of the 31st International Conference on Ocean, Offshore and Arctic Engineering (OMAE2012). 1-6 July 2012 - Rio de Janeiro, Brazil
/55/ Swithenbank, S.B. and Larsen, C.M. (2012): “Occurrence of high amplitude VIV with time sharing”, OMAE2012-83431, Rio de Janeiro, Brazil
/56/ Rustad, A.M., Ervik, A.K., Sørensen, A.J. and Larsen, C.M. Increasing the Operation Window for Drilling Risers on DP Vessels by Monitoring Riser Angles (OMAE2012-83922). Proceedings of the 31st International Conference on Ocean, Offshore and Arctic Engineering (OMAE2012). 1-6 July 2012 - Rio de Janeiro, Brazil.
/57/ Larsen, C.M., Passano, E. and Lie, H.: Recent development of the empirical basis for prediction of vortex induced vibrations, Proceedings of the of the International Conference on Hydroelastisity in Marine Technology 2012 Tokyo, JAPAN
