Peter Davies & Morten Boegild - Tidal turbine array modelling, influence of waves on turbine wakes
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Lloyd's Register Energy presented on modelling techniques for tidal arrays. They discussed their previous work modelling single turbines and arrays using computational fluid dynamics. Their goals for array simulations were to investigate turbine loading, power performance, and wakes with and without waves. They demonstrated steady state simulations of a 3x3 tidal turbine array using multiple rotating reference frames with and without kinematic waves included. The results showed the turbine wake was influenced by waves and their choice of wave modelling depended on parameters like wave height and period. They concluded by discussing continuing their investigation of turbines' influence on free surfaces and comparing simulation software.
Peter Davies & Morten Boegild - Tidal turbine array modelling, influence of waves on turbine wakes
- 1. Lloyd’s Register Energy Modelling techniques for tidal arrays All Energy – Aberdeen Lloyd’s Register Marine Renewable Energy Research Peter Davies Global Technology Leader Renewable Energy Energy Technology Directorate Co presenter: Morten Ryge Bøgild Consultant Energy, Fluid Dynamics Lloyd's Register ODS 22nd & 23rd May 2013
- 2. Lloyd’s Register Energy Agenda • Introduction to Lloyd’s Register • Previous work in tidal modelling • Simulation goals • Model setup • Wave modelling techniques • Steady state array simulations with and without waves
- 3. Lloyd’s Register Energy Our services to the energy industry • regulation compliance assessment and consultancy • risk consultancy • optimising risk-based inspection • asset management system certification • asset integrity management with bespoke software solutions. Lloyd’s Register offers expert advise for safe and efficient power generation, transmission and distribution. Our services cover: Convering renewable energy, oil and gas, nuclear, thermal energy and manufacturing sectors 245 Offices in 186 Countries
- 4. Lloyd’s Register Energy Previous work in tidal modelling • Modelling of tidal turbines using open source software - presented at All Energy last year • Modelling of tidal turbines using CFD both single turbines and arrays: • The multipe rotating reference frames (MRF): Steady-state analysis, produces a snap-shot in time (fast) • The rigid body motion (RBM): Full transient solution for a rotating turbine • See paper presented at Marine & Offshore Renewable Energy, 26-27 September 2012, London, UK
- 5. Lloyd’s Register Energy Tidal velocity measurements depth vs time Update on EMEC activities, resource description, and characterisation of wave-induced velcities in a tidal flow ~Norris & Droniou 2007
- 6. Lloyd’s Register Energy Tidal velocity measurements depth vs time Update on EMEC activities, resource description, and characterisation of wave-induced velcities in a tidal flow ~Norris & Droniou 2007
- 7. Lloyd’s Register Energy Simulation goals • Turbine loading and power performance • Investigate and compare wake with and without waves To do this: • fully discretized numerical simulation of 3x3 tidal turbine array using STAR CCM+ and ANSYS CFX.
- 8. Lloyd’s Register Energy Modelling • Domain size: Width x length x depth: 540 x 560 x 45 m. 22.8 m 150 m120 m
- 9. Lloyd’s Register Energy Modelling • Inlet velocity profile: • Mesh size in the order of 9 million for 3x3 array. • Rotor may be stationary with rotating flow in the subdomain around it; MRF. • Or rotor may be rotating in a subdomain with mesh; Sliding interface / RBM. • Rotor speed adjusted to match generator:
- 10. Lloyd’s Register Energy Steady state MRF no waves • Inlet velocity 2.5 m/s at hub height. • Wake zone behind turbines reduces velocity by 30 %.
- 11. Lloyd’s Register Energy Settings • Velocity profiles - modified by influence of turbines
- 12. Lloyd’s Register Energy Results Array Layout
- 13. Lloyd’s Register Energy Results Array Layout
- 14. Lloyd’s Register Energy Wave modelling • Free surface waves • Waves defined at the inlet – travels through the domain • Computational intensive – diffusive if mesh is not refined in interface region • Can model situations where waves are disturbed by the turbine • Kinematic waves • Waves are specified by velocity components at the inlet and the top boundary • Able to model wave impact on tidal turbine but cannot model the tidal turbine effect on the waves Fig. from: Westphalen et al. “Simulation of Extreme Free Surface Waves using STAR CCM+ and CFX11” (2008)
- 15. Lloyd’s Register Energy Steady state MRF kinematic waves • Inlet velocity 2.5 m/s at hub height. 3 m waves, T = 6 s. • Wake zone behind turbines increases velocity due to influence of streamwise waves.
- 16. Lloyd’s Register Energy Steady state MRF kinematic waves With waves No waves
- 17. Lloyd’s Register Energy Conclusion • Fully discretized 3x3 tidal array modelling was simulated with and without wave modelling using the MRF rotor simulation. • Flow distribution and turbine performance in tidal array are possible outcomes. • It has been demonstrated that the turbine wake is influenced by waves; this is dependent on turbine design, wave height, period and water depth. • The choice of either modelling the free surface or using the kinematic description depends on the above parameters. • We are continuing to investigate the turbines influence on the free surface. • We are continuing to compare STAR CCM+ and ANSYS CFX.
- 18. Lloyd’s Register Energy ANY QUESTIONS ? Thank you for listening
- 19. Lloyd’s Register is a trading name of the Lloyd’s Register Group of entities. Services are provided by members of the Lloyd's Register Group. For further information visit www.lr.org/entities For more information, please contact: Peter Davies Renewable Energy Global Technology Leader Lloyd’s Register Group Services Ltd Denburn House, 25 Union Terrace Aberdeen, AB10 1NN T +44 (0)1224 267771 E peter.davies@lr.org w www.lr.org/renewables