SuperGen UK Centre for Marine Energy Research Annual Assembly 2014

X-MED: EXTREME LOADING OF MARINE ENERGY DEVICES DUE TO WAVES,

CURRENTS, FLOTSAM AND MAMMAL IMPACT

.

UKCMER

UKCMER Consortium of the Universities of Manchester, Edinburgh and Plymouth and the Scottish Association for Marine Sciences (SAMS) led by Peter Stansby of University of Manchester Manchester : Peter Stansby, Tim Stallard, Ben Rogers, David Apsley, Imran Afgan RAs: Tong Feng, Stefano Rolfo, Stephen Longshaw, Umair Ahmed Additional inputs: James McNaughton , Emmanuel Fernando Rodriguez Edinburgh : Tom Bruce RA: Gregory Payne Plymouth : Deborah Greaves, Alison Raby RA now lecturer: Martyn Hann SAMS : Ben Wilson

Aim : To identify and improve understanding of extreme loading on tidal stream turbines and wave energy devices by modelling and experiments

UKCMER

• WAVE ENERGY DEVICES design sea states in waves and currents for a taut moored floating body representative of a wave energy device or support structure

Objectives: • TIDAL STREAM TURBINES 1. tidal turbulence, wake turbulence in arrays 2. swell wave loading 3. impact of flotsam (containers) and marine animals

UKCMER

Other projects contributing ETI projects: ReDAPT (Reliable Data Acquisition Platform for Tidal) PerAWAT (Performance Assessment of Wave And Tidal array systems) EPSRC Newton fund: ALL-TTidal: Arrays of long-life turbines for tidal X-MED extended to end April 2015

What does turbine flow look like?

vorticity

CFD

Shear layers

Self similar far wake Rotational near wake

Vorticity plots

UKCMER

Stallard, Feng, Stansby 2014 J. Fluids Struct. Experimental study of the mean wake of a tidal stream rotor in a shallow turbulent flow

Manchester turbine experiments

Extreme value probability distributions of thrust

1.1 1.2 1.3 1.4 1.5 1.6 1.7

10%

1%

0.1%

0.01%

F1/100 = 1.38

F1/1000 = 1.53

F1/10000 = 1.64

P ( F

> F

1/n )

F1/n / F0

1.1 1.2 1.3 1.4 1.5 1.6 1.710%

1%

0.1%

0.01%

F1/100 = 1.38

F1/1000 = 1.5

F1/10000 = 1.59

F1/n / F0

1.1 1.2 1.3 1.4 1.5 1.6 1.710%

1%

0.1%

0.01%

F1/100 = 1.38

F1/1000 = 1.5

F1/10000 = 1.59

F1/n / F0

Normal Weibull Type 1 Pareto Onset turbulence intensity 12%

Turbulent flow and waves

superimpose wave drag with CD=2.0, CT =0.9 unchanged

Fernando Rodriguez, Stallard, Stansby 2014 Experimental study of extreme thrust on a tidal stream rotor due to turbulent flow and with opposing waves, J Fluids Struct, 51, 354-361

Turbine CFD Code_SATURNE

LES and RANS

Lab scale Tidal Stream Turbine (TST)

A.S. Bahaj, et al2007 Renewable Energy, 32(3), 407-426

EMEC velocity profiles (ReDAPT) Velocity profiles selected to represent wide range of profiles occurring at similar flow speed. All velocity profiles to have same depth averaged velocity (1.8 m/s). Benchmark case performed with uniform flow. Velocity profiles chosen to assess effect of shear: Flood (FA1) and Ebb (ED1)

LES results

Streamwise mean velocity showing approach flow turbulence and near wake of the turbine rotor and support tower

Streamwise vorticity Q, effects of shear and support tower evident

Spectrum of blade bending moment at r/R=0.272

Field data

No inflow turbulence

Turbulent inflow

Aspley et al. (in consideration for presentation at EWTEC2015)

Marine animal impact

Minke whale

Idealised physical model

SPH and LSM

Extreme wave impacts on a floating wave energy converter

Completed experimental tests include: 1. Individual focused wave groups of

increasing steepness. 2. Individual plunging breaking waves,

breaking at different locations. 3. NewWaves embedded into random

time series. 4. Embedded NewWaves with

transverse currents at three different speeds.

5. Embedded and individual NewWaves with directionality.

STAR-CCM+ simulations: - Successful reproduction of decay

tests - Successful reproduction of wave

generation

Embedded NewWave experiments

• Embedded NewWave tests conducted to capture the influence of the model’s motion history on mooring loads.

• Ninety cases tested, 120 seconds long, with the NewWave embedded at 60 seconds.

50 55 60 65 70-1

-0.5

0

0.5

1

time (sec)

surfa

ce e

leva

tion

/ New

Wav

e am

plitu

de

Random backgroundIndividual NewWaveEmbedded NewWave

Embedded NewWave experiments • Distribution of peak mooring load generated by the embedded focused

wave.

• 84 % of cases generated a peak load greater than the individual focused wave.

• Recorded motions analysed to identify properties of the previous motions which result in the largest mooring loads.

Numerical simulations • Experimental data (non-

breaking, breaking and embedded cases) are being used for validation and comparison of various numerical models:

- STAR-CCM+ - SPH (University of Manchester) - OpenFOAM (Ed Ransley – EPSRC funded PhD student) - DNV.GL WaveDyn model

Open Foam simulation of X-MED non-breaking experiments. E Ransley (2014)

UKCMER

SPH Numerical Wave Tank

Omidvar,P., Stansby,P.K. and Rogers,B.D. 2012 SPH for 3-D floating bodies using variable particle mass distribution, Int. J. Numer. Methods in Fluids, DOI: 10.1002/fld.3749

IMPROVED SOLID BOUNDARY CONDITIONS DEVELOPED AND TO BE IMPLEMENTED AND CASES RUN

To do : Larger scale turbine experiments 1.2m diameter (1:15) • At IFREMER in January and March • Diameter/depth as Manchester model • Tests in currents and with waves, impacts

Designed by Gregory Payne and Tim Stallard

Impact: dry test on blade support

22kN load cell

High tensile spring And angular speed measurement

‘Blade’ (square section)

Target: PTFE with rubber ‘skin’ (same material as Minke whale model)

X-MED, University of Edinburgh

To do : small scale turbine experiments

• Increased turbulence intensity - 17% • Thrust/power measurements of turbine in

wake of upstream turbine • Very long runs to be analysed

Turbine CFD to do

• Channel flow at very high Re No = 630k, competed at lower Re No

• Effect of upstream wake on turbine

• Papers to date: • Afgan,I., McNaughton,J., Rolfo,S., Apsley,D., Stallard,T., and Stansby,P. 2013 Turbulent flow and

loading on a tidal stream turbine by LES and RANS. Int. J. Heat and Fluid Flow, 43, 96-108, THMT special issue

• McNaughton, J., Afgan, I., Apsley, D.D., Rolfo, S., Stallard, T. And Stansby, P.K. 2014 A simple sliding-mesh interface procedure and its application to the CFD simulation of a tidal-stream turbine, Int. J.Numer. Methods in Fluids, 74, 250-269

• Jarrin,N., Prosser,R., Uribe,J., Benhamadouche,S., Laurence,D. 2009 Reconstruction of turbulent fluctuations using a synthetic eddy model, Int J Heat Fluid Flow, 30, 435-442

Thanks and Questions

Acknowledgements ETI PerAWaT - equipment and data developed as part of WG4WP2 of “Performance Assessment of Wave and Tidal array systems (PerAWaT)” commissioned by the Energy Technologies Institute. (2009-2013). ETI ReDAPT - enabled collection of full-scale flow data ETI ReDAPT and EDF – supported development and evaluation of CFD methods.

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