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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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