I. Introduction/Background Section II Section III Section IV V. Conclusions

Modelling mooring line non-linearities (materialand geometric effects) for a wave energy converter

using AQWA, SIMA and Orcaflex

Majid A. Bhinder 1 Madjid Karimirad 2 Sam Weller 3

Yannick Debruyne 4 Matthieu Guerinel 4 Wanan Sheng 1

1MaREI, University College Cork, Ireland

2MARINTEK, Norway

3University of Exeter, UK

4WavEC - Offshore Renewables, Lisbon, Portugal

September 9, 2015MA Bhinder, M Karimirad, S Weller, Y Debruyne, M Guerinel, and W Sheng.Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex.11th European Wave and Tidal Energy Conference EWTEC 2015, Nantes, France. 1/23

I. Introduction/Background Section II Section III Section IV V. Conclusions

Problem description

Figure: Device comprising semi-taut mooring scope of three mooring lines

MA Bhinder, M Karimirad, S Weller, Y Debruyne, M Guerinel, and W Sheng.Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex.11th European Wave and Tidal Energy Conference EWTEC 2015, Nantes, France. 2/23

I. Introduction/Background Section II Section III Section IV V. Conclusions

Device schematic Problem description

Figure: Device schematicMA Bhinder, M Karimirad, S Weller, Y Debruyne, M Guerinel, and W Sheng.Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex.11th European Wave and Tidal Energy Conference EWTEC 2015, Nantes, France. 3/23

I. Introduction/Background Section II Section III Section IV V. Conclusions

Modelling tools

Modelling packagesSimulations were performed using three mainstream modeling pack-ages:

ANSYS AQWAa,SIMAb

Orcaflexc

aANSYS AQWA v14.5 - ANSYS Inc (http://www.ansys.com)bSIMA v - (https://www.sintef.no/home/marintek/)cOrcaflex v 9.6 - (http://www.orcina.com/)

MA Bhinder, M Karimirad, S Weller, Y Debruyne, M Guerinel, and W Sheng.Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex.11th European Wave and Tidal Energy Conference EWTEC 2015, Nantes, France. 4/23

I. Introduction/Background Section II Section III Section IV V. Conclusions

Modelling tools & simulation setup

SIMA1st order wave loads(from WAMIT)Mean drift

Newmark-Beta method

123 elements per line(Total line length:417m)Time step: 0.01s

Orcaflex1st order wave loads(from WAMIT)2nd order wave driftQTFs (Quadratic Trans-fer Functions) – New-man’s approximationExplicit scheme

127 elements per line

Time step: 0.01s

AQWA1st order wave loads(from AQWA)2nd order wave driftQTFs – Newman’s ap-proximation and slowdrift option2 stage implicit (semi-implicit for the non-lineardrag term) predictor-corrector scheme basedon the Newmark-Betamethod100 elements ( Maxi-mum of 250 elementscan be defined per moor-ing line)Time step: 0.01s

MA Bhinder, M Karimirad, S Weller, Y Debruyne, M Guerinel, and W Sheng.Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex.11th European Wave and Tidal Energy Conference EWTEC 2015, Nantes, France. 5/23

I. Introduction/Background Section II Section III Section IV V. Conclusions

Primary cases

Material non-linearity

Geometric non-linearity

Fluid non-linearity

MA Bhinder, M Karimirad, S Weller, Y Debruyne, M Guerinel, and W Sheng.Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex.11th European Wave and Tidal Energy Conference EWTEC 2015, Nantes, France. 6/23

I. Introduction/Background Section II Section III Section IV V. Conclusions

MATERIAL NON-LINEARITY OF SYNTHETIC ROPESCases

1 Baseline (Hs = 2.5m, Tp=10s (Tz = 4.98s), dir = 0◦, constant stiffness)2 EA13 EA2

0 5 10 15 20 25 300

1000

2000

3000

4000

Strain [%]

Load

[kN

]

11th loading cycle−−Case EA1

500th loading cycle−−Case EA2

Figure: Nylon rope load-strain curve based on the load-to-failure test of asimilar construction (TTI/Bridon)

MA Bhinder, M Karimirad, S Weller, Y Debruyne, M Guerinel, and W Sheng.Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex.11th European Wave and Tidal Energy Conference EWTEC 2015, Nantes, France. 7/23

I. Introduction/Background Section II Section III Section IV V. Conclusions

MATERIAL NON-LINEARITY OF SYNTHETIC ROPESModelling Representation

Representation of Axial Stiffness in Three Numerical CodesAQWA SIMA OrcaFlexConstant axial stiffness Constant axial stiffness Constant axial stiffnessNon-linear EA-strainvalues

Non-linear load strainvalues

Non-linear load strainvalues

MA Bhinder, M Karimirad, S Weller, Y Debruyne, M Guerinel, and W Sheng.Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex.11th European Wave and Tidal Energy Conference EWTEC 2015, Nantes, France. 8/23

I. Introduction/Background Section II Section III Section IV V. Conclusions

Results Material nonlinearity

A1 A2 A3 B1 B2 B30

500

1000

1500

2000

2500

3000

3500

4000

4500

Max

tens

ion

[kN

]

A: anchor, B: fairlead connection

A1 A2 A3 B1 B2 B30

500

1000

1500

2000

2500

3000

3500

4000

Mea

n te

nsio

n [k

N]

A: anchor, B: fairlead connection

A1 A2 A3 B1 B2 B30

50

100

150

200

ST

D te

nsio

n [k

N]

A: anchor, B: fairlead connection

Baseline−AQWABaseline−OrcaBaseline−SIMA

Case EA1−AQWACase EA1−OrcaCase EA1−SIMA

Case EA2−AQWACase EA2−OrcaCase EA2−SIMA

← Maximum tension

← Mean tension

← Stdv tension

MA Bhinder, M Karimirad, S Weller, Y Debruyne, M Guerinel, and W Sheng.Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex.11th European Wave and Tidal Energy Conference EWTEC 2015, Nantes, France. 9/23

I. Introduction/Background Section II Section III Section IV V. Conclusions

Results Material nonlinearityA1 A2 A3 B1 B2 B30

50

100

150

200

ST

D te

nsio

n [k

N]

A: anchor, B: fairlead connection

Baseline−AQWABaseline−OrcaBaseline−SIMA

Case EA1−AQWACase EA1−OrcaCase EA1−SIMA

Case EA2−AQWACase EA2−OrcaCase EA2−SIMA

A1 A2 A3 B1 B2 B30

500

1000

1500

2000

2500

3000

3500

4000

4500

Max

tens

ion

[kN

]

A: anchor, B: fairlead connection

(a) Maximum line tensions at anchor and at fairlead connection pointsfor three cases: the Baseline, Case EA1, and Case EA2

MA Bhinder, M Karimirad, S Weller, Y Debruyne, M Guerinel, and W Sheng.Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex.11th European Wave and Tidal Energy Conference EWTEC 2015, Nantes, France. 10/23

I. Introduction/Background Section II Section III Section IV V. Conclusions

Results Material nonlinearityA1 A2 A3 B1 B2 B30

50

100

150

200

ST

D te

nsio

n [k

N]

A: anchor, B: fairlead connection

Baseline−AQWABaseline−OrcaBaseline−SIMA

Case EA1−AQWACase EA1−OrcaCase EA1−SIMA

Case EA2−AQWACase EA2−OrcaCase EA2−SIMA

A1 A2 A3 B1 B2 B30

500

1000

1500

2000

2500

3000

3500

4000

Mea

n te

nsio

n [k

N]

A: anchor, B: fairlead connection

(b) Mean line tensions at anchor and at fairlead connection points forthree cases: the Baseline, Case EA1, and Case EA2

MA Bhinder, M Karimirad, S Weller, Y Debruyne, M Guerinel, and W Sheng.Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex.11th European Wave and Tidal Energy Conference EWTEC 2015, Nantes, France. 11/23

I. Introduction/Background Section II Section III Section IV V. Conclusions

Results Material nonlinearity

A1 A2 A3 B1 B2 B30

50

100

150

200

ST

D te

nsio

n [k

N]

A: anchor, B: fairlead connection

Baseline−AQWABaseline−OrcaBaseline−SIMA

Case EA1−AQWACase EA1−OrcaCase EA1−SIMA

Case EA2−AQWACase EA2−OrcaCase EA2−SIMA

(c) Standard deviation (STD) line tensions at anchor and at fairleadconnection points for three cases: the Baseline, Case EA1, and CaseEA2

MA Bhinder, M Karimirad, S Weller, Y Debruyne, M Guerinel, and W Sheng.Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex.11th European Wave and Tidal Energy Conference EWTEC 2015, Nantes, France. 12/23

I. Introduction/Background Section II Section III Section IV V. Conclusions

Case studies Geometric nonlinearity

Cases1 Baseline (Hs = 2.5m, Tp=10s (Tz = 4.98s), dir = 0◦, constant stiffness)2 Simplified spring

Table: Constant Stiffness Values for the Simplified Model

Mode Stiffness [N/m]Surge 7.64e04Sway 7.67e04Yaw 1.21e07

MA Bhinder, M Karimirad, S Weller, Y Debruyne, M Guerinel, and W Sheng.Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex.11th European Wave and Tidal Energy Conference EWTEC 2015, Nantes, France. 13/23

I. Introduction/Background Section II Section III Section IV V. Conclusions

Results Geometric nonlinearity

Surge Sway Heave Roll Pitch Yaw−2

0

2

4

6

8

Res

pons

e [m

] or

[deg

]

Motion mode

Surge Sway Heave Roll Pitch Yaw−0.4

−0.2

0

0.2

0.4

0.6

0.8

1

1.2

Res

pons

e [m

] or

[deg

]

Motion mode

Surge Sway Heave Roll Pitch Yaw0

0.2

0.4

0.6

0.8

1

1.2

1.4

Res

pons

e [m

] or

[deg

]

Motion mode

Baseline−AQWABaseline−OrcaBaseline−SIMA

Simplified−AQWASimplified−OrcaSimplified−SIMA

← Maximum response

← Mean response

← Stdv response

MA Bhinder, M Karimirad, S Weller, Y Debruyne, M Guerinel, and W Sheng.Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex.11th European Wave and Tidal Energy Conference EWTEC 2015, Nantes, France. 14/23

I. Introduction/Background Section II Section III Section IV V. Conclusions

Results Geometric nonlinearitySurge Sway Heave Roll Pitch Yaw0

0.2

0.4

0.6

0.8

1

1.2

1.4

Res

pons

e [m

] or

[deg

]

Motion mode

Baseline−AQWABaseline−OrcaBaseline−SIMA

Simplified−AQWASimplified−OrcaSimplified−SIMA

Surge Sway Heave Roll Pitch Yaw−2

0

2

4

6

8

Res

pons

e [m

] or

[deg

]

Motion mode

(d) Maximum displacement from two case studies: Baseline, Simplified

MA Bhinder, M Karimirad, S Weller, Y Debruyne, M Guerinel, and W Sheng.Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex.11th European Wave and Tidal Energy Conference EWTEC 2015, Nantes, France. 15/23

I. Introduction/Background Section II Section III Section IV V. Conclusions

Results Geometric nonlinearitySurge Sway Heave Roll Pitch Yaw0

0.2

0.4

0.6

0.8

1

1.2

1.4

Res

pons

e [m

] or

[deg

]

Motion mode

Baseline−AQWABaseline−OrcaBaseline−SIMA

Simplified−AQWASimplified−OrcaSimplified−SIMA

Surge Sway Heave Roll Pitch Yaw−0.4

−0.2

0

0.2

0.4

0.6

0.8

1

1.2

Res

pons

e [m

] or

[deg

]

Motion mode

(e) Mean value of displacements from two case studies: Baseline, Sim-plified

MA Bhinder, M Karimirad, S Weller, Y Debruyne, M Guerinel, and W Sheng.Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex.11th European Wave and Tidal Energy Conference EWTEC 2015, Nantes, France. 16/23

I. Introduction/Background Section II Section III Section IV V. Conclusions

Results Geometric nonlinearitySurge Sway Heave Roll Pitch Yaw0

0.2

0.4

0.6

0.8

1

1.2

1.4

Res

pons

e [m

] or

[deg

]

Motion mode

Baseline−AQWABaseline−OrcaBaseline−SIMA

Simplified−AQWASimplified−OrcaSimplified−SIMA

Surge Sway Heave Roll Pitch Yaw0

0.2

0.4

0.6

0.8

1

1.2

1.4

Res

pons

e [m

] or

[deg

]

Motion mode

Baseline−AQWABaseline−OrcaBaseline−SIMA

Simplified−AQWASimplified−OrcaSimplified−SIMA

(f) Standard deviation (STD) of displacement from two case studies:Baseline, Simplified

MA Bhinder, M Karimirad, S Weller, Y Debruyne, M Guerinel, and W Sheng.Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex.11th European Wave and Tidal Energy Conference EWTEC 2015, Nantes, France. 17/23

I. Introduction/Background Section II Section III Section IV V. Conclusions

NON-LINEAR VISCOUS FLUID DAMPINGFluid nonlinearity

Cases

1 Case C1: Flood peak velocity = 1.132m/s, direction = 0degrees (WAMIT heading).

2 Case C2: Flood peak velocity = 4.554m/s, direction = 0degrees (WAMIT heading).

MA Bhinder, M Karimirad, S Weller, Y Debruyne, M Guerinel, and W Sheng.Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex.11th European Wave and Tidal Energy Conference EWTEC 2015, Nantes, France. 18/23

I. Introduction/Background Section II Section III Section IV V. Conclusions

Cases Fluid nonlinearity

Table: Maximum Current Speed at Center of Water Column for TwoTest Sites

Site Max ebb velocity[m/s]

Max flood velocity[m/s]

Pentland Firth 4.77 4.54Wave Hub 0.85 0.9

Flood and ebb current profiles based on (left) Wave Hub

ADCP and (right) Pentland Firth measurements.

MA Bhinder, M Karimirad, S Weller, Y Debruyne, M Guerinel, and W Sheng.Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex.11th European Wave and Tidal Energy Conference EWTEC 2015, Nantes, France. 19/23

I. Introduction/Background Section II Section III Section IV V. Conclusions

Drag coefficients Fluid nonlinearity

Drag Coefficients for Different Types of Mooring ComponentsWithout Marine Growth, Longitudinal Values are only Consideredfor Chains1.

Type Transverse LongitudinalStud chain 2.6 1.4Studless chain 2.4 1.15Stranded rope 1.8 –Spiral rope without plastic sheathing 1.6 –Spiral rope with plastic sheathing 1.2 –Fibre rope 1.6 –

1D. N. Veritas, Position mooring, DNV-OS-E301, 2013

MA Bhinder, M Karimirad, S Weller, Y Debruyne, M Guerinel, and W Sheng.Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex.11th European Wave and Tidal Energy Conference EWTEC 2015, Nantes, France. 20/23

I. Introduction/Background Section II Section III Section IV V. Conclusions

Results Fluid nonlinearity

A1 A2 A3 B1 B2 B3600

800

1000

1200

1400

1600

1800

Max

tens

ion

[kN

]

A: anchor, B: fairlead connection

A1 A2 A3 B1 B2 B3400

600

800

1000

1200

1400

1600

Mea

n te

nsio

n [k

N]

A: anchor, B: fairlead connection

A1 A2 A3 B1 B2 B30

20

40

60

80

100

120

ST

D te

nsio

n [k

N]

A: anchor, B: fairlead connection

Case C1−AQWACase C1−OrcaCase C1−SIMA

Case C2−AQWACase C2−OrcaCase C2−SIMA

← Maximum tension

← Mean tension

← Stdv tension

MA Bhinder, M Karimirad, S Weller, Y Debruyne, M Guerinel, and W Sheng.Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex.11th European Wave and Tidal Energy Conference EWTEC 2015, Nantes, France. 21/23

I. Introduction/Background Section II Section III Section IV V. Conclusions

Conclusions

Material nonlinearity: The results from different simulation codes agree ingeneral. It has been found that material non-linearities have asignificant effect on both the simulated line tensions and deviceresponses.

Geometric effects: It is shown that the motion responses from the Simplifiedmodel are in reasonable agreement with the Baseline modeland numerical packages demonstrated this trend, however inOrca results the Simplified model showed relatively amplifiedresponse in particular for pitch and heave motion.

Fluid non-linearity: The capability of the packages is assessed through twocase studies comprising individual, depth-dependent currentprofiles. Agreement between the simulation results of the threesoftware packages was achieved.

MA Bhinder, M Karimirad, S Weller, Y Debruyne, M Guerinel, and W Sheng.Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex.11th European Wave and Tidal Energy Conference EWTEC 2015, Nantes, France. 22/23

I. Introduction/Background Section II Section III Section IV V. Conclusions

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Thank you for your attention.

MA Bhinder, M Karimirad, S Weller, Y Debruyne, M Guerinel, and W Sheng.Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex.11th European Wave and Tidal Energy Conference EWTEC 2015, Nantes, France. 23/23