NORCOWE Science Meet Industry Bergen

PREDICTIONS OF WAVE FORCES ON

JACKET FOR WIND TURBINES

8th of November 2016 Tron Solberg

Agenda

• Objective

• Acona Flow Technology (AFT)

• Norcowe projects

• Wave channel experiments

• Jacket geometry

• Wave elevation

• Wave loads

• Concluding remarks

• Develop a reasonably validated CFD

model for wave forces on marine

structures including wave slamming

Objective

Acona Flow Technology

• One of Norway’s most senior environment

within flow modelling and simulation services

• 3 out of 8 have PhD

• 18 years average industrial experience

• Independent consultancy services within:

– Blowout & wellkill studies

– Flow assurance

– Computational fluid dynamics

• State-of-the art simulation softwares

• Powerful simulation cluster

Blowout Contingency Planning

30" Conductor

197 m MD / TVD RKB

Seabed 137 m RKB

8 1/2" OH TD 2082 MD / 2082 m TVD RKB

RKB-MSL 22m

Drilling

BOP

Sealevel

Intersection

1699 m TVD RKB

9 5/8" liner

1699 m MD / TVD RKB

13 ⅜"csg

1200 m MD / TVD RKB

20" csg

600 m MD / TVD RKB

Top Shetland:

1699 m TVD RKB

TOL

1150 m MD / TVD RKB

Top Draupne:

1882 m TVD RKB

Top Basement:

1933 m TVD RKB

Environment Risk Assessement

• Stochastic oil drift simulations (~10 000)

• Resolution down to 50 m

• Environmental resource data (e.g. Birds)

• Overlap analysis

• Between each oil simulation and the resource (birds)

• Statistics for:

• Relative population loss

• Restitution time for population

• Probability maps for spill at

location

Bird

data Oil data

Oil - bird

overlap

OIL

Wind turbine -

Wind/wave

interaction

Subsea cage

hatch

Tidal turbine

Computational Fluid DynamicsMarine engineering applications

Fish farm-

Wave/structure

interaction

Norcowe projects

Wave-wind interactions and

implications for offshore wind turbinesBreaking wave forces on offshore wind turbine

jackets in shallow water

Siri Kalvig (2014) PhD thesis, UiS

Ongoing PhD work of Jithin Jose at Uis

Wind respons to opposing (left) and aligned (right) swell

Influence of waves on wind turbines

Close collaboration with University of Stavanger

Wave Channel Experiments

• Large Wave Flume

– FZK-GWK Hannover

• Wave channel data

– (LxWxD)=(300,5,7) m

– Height plateau 2.3 m

– Slope 1:10

– SWL 4.3 m

– Jacket 198.37 m downstream

• Measurement equipments

– Force transducers

– Wave gauges

– Velocity gauges

Wave height Wave period

[m] [s]

1.6 5.2

1.7 5.2

1.8 5.2

1.6 5.55

1.7 5.55

1.8 5.55

1.6 4.9

1.7 4.9

1.8 4.9

1.6 4.6

1.7 4.6

1.8 4.6

Jacket Geometry – 1:8 scale

Front Left Right

2250 2250 2250

2000

2710

SWL (4300)

MAX (5675)

140

140

Dimensions in [mm]

EL (2300)

Wave Elevation

Breaking position: Behind the last leg

H=1.6 m

T= 5.2 s

Wave Elevation

Non-linear waves

H~1.6 m

T~5.2 s

Plunging breakers

Fx

Fz

Fy

Wave Loads - Total

D MF F F

Non-breaking waves:

Morrison equation

Breaking waves:

D M SF F F F

Slamming force

20S w S b bF t C RC

Drag:D w DdF C u u dz

Inertia: 2

M w M

dudF C R dz

d z

Measurements: First peak larger than second

Wave Loads – Front vertical member Max slamming force on V1

V1

B1

B2

H=1.7m

T=5.55s

Total force on jacket

Local forces on transducer V1aa

b

b

Concluding remarks

• CFD model for predicting wave loads on offshore wind-turbine jacket established

• Numerical local force transducer developed

• Able to predict local slamming coefficients

• Preliminary results are promising compared to measurements

• Detailed comparison with measurements remains