MAST/SRDG-oct2010-susana baston
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The document summarizes research using the SUNTANS model to understand hydrodynamics in the Pentland Firth region between Orkney and mainland Scotland. It describes how the model works, how it has been implemented in the Pentland Firth region using site-specific bathymetry and tidal data, and outlines future work including model calibration, comparison to other models, and coupling with wave and ecological models to better understand the environment and tidal energy resource.
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MAST/SRDG-oct2010-susana baston
- 1. Hydrodynamics in the Pentland Firth: Understanding the energy resource Orkney, 20th August 2010 Dr. Susana Bastón Meira Research associate in the ICIT- International Centre for Island Technology
- 2. Contents 1. Motivation 2. SUNTANS model 3. Implementation to the Pentland Firth 4. Future work 5. Conclusions Orkney, 20th October 2010
- 3. Orkney, 20th October 2010 Motivation Mainland Scotland Hoy Mainland Orkney PENTLAND FIRTH ORKNEY
- 4. Orkney, 20th October 2010 Motivation The Physical environment and the ecology of the Pentland Firth are still not well understood Better picture of baseline environmental conditions must be done
- 5. Motivation How good is the energy source? How is the energy dissipated? Long term and far-field effects Orkney, 20th October 2010 Uncertainty in Forcing ‣ Changes in Tidal forcing ‣ Hydrographic Changes Uncertainty in Underlying Processes ‣ Scales of resolution ‣ Water column structure ‣ Turbulence closure ‣ Sediment TransportUncertainty in Far-Field effects ‣ Shoreline changes ‣ Nutrients transport
- 6. Motivation Initial site selection, mitigate impacts, maximise efficiency Predict effects of installation of MECs and harness energy from a flow field Monitoring tool both time and cost efficient Near and far field spatial information Long term temporal modelling Accurate predictions of nutrients and sediment transport in coastal waters Orkney, 20th October 2010
- 7. SUNTANS model SUNTANSSUNTANS is a numerical model designed for the simulation of complex, non-hydrostatic coastal, river and estuarine flows with high resolution on unstructured grids using parallel computers. Orkney, 20th October 2010
- 8. SUNTANS model Navier-Stokes simulator means that solve the Navier-Stokes equations: u, v, w are Cartesian components of velocity u is the vector form of velocity q is the non-hydrostatic component of pressure η is the free surface elevation f and b are the Coriolis terms υH and υV are the horizontal and vertical turbulent eddy viscosities ∇H the horizontal gradient operator: Orkney, 20th October 2010
- 9. SUNTANS model Open source: Accessible to research Three-dimensional approach to resolve vertical Unstructured grid: Provides exceptional resolution around fine-scale features Parallel Implementation facilitates high resolution Orkney, 20th October 2010 Resource: Dr Rob Harris1 , Dr Karl Stephen2 , Prof Margot Gerritsen3 1.- ICIT/HWU, 2.- IPE/HWU, 3.- Stanford University
- 10. SUNTANS model SUNTANS is Non-hydrostatic: When a fluid is in motion, the vertical pressure gradient is also influenced by the vertical acceleration and friction non-hydrostatic pressure effects P = p + q Static pressure + Dynamic pressure • Bottom density currents at high latitudes • Super critical flows related to topography in fjords and inlets Hydrostatic approximation: Equilibrium between pressure gradient and gravitational force Orkney, 20th October 2010
- 11. Implementation to the Pentland Firth Orkney, 20th October 2010 1 43 2
- 12. Implementation to the Pentland Firth Orkney, 20th October 2010 OSU TOPEX/POSEIDON Global inverse solution Boundary conditions Bathymetry interpolated onto the grid
- 13. Implementation to the Pentland Firth Orkney, 20th October 2010 West Side East Side
- 14. Implementation to the Pentland Firth Orkney, 20th October 2010
- 15. Implementation to the Pentland Firth Orkney, 20th October 2010
- 16. Future Work Orkney, 20th October 2010 Calibration using ADCP data Comparison with other numerical models Coupling SUNTANS with wave models Coupling with ecological models
- 17. There is a requirement for cost effective accurate long term spatial modelling of the environment and a clearer understanding of physical conditions SUNTANS model is a valuable tool, capable of providing information leading to a better understanding of the source and intervention effects at MEC sites. Once we have the model validated we can implement it to another areas of interest in Orkney SUNTANS is a powerful research instrument Conclusions Orkney, 20th October 2010
- 18. Thanks for your attention! Email: S.Baston@hw.ac.uk http://www.icit.org.uk/
Notes de l'éditeur
- I’ll talk about the need of a baseline understanding of physical processes which let us evaluate the potential environmental impacts induced by MRE installations. The structure of this presentation is as follows First, the motivation of this work. Then I’ll introduce the SUNTANS model I’ll talk about their implementation to the Pentland Firth to finish with future work and conclusions
- I am sure that everybody here knows where is the Pentland Firth, but if anyone doesn’t Pentland Firth is the highly dynamic channel that separate Orkney to Mainland Scotland.
- The Pentland Firth and Orkney waters have been recently provided with licences by Crown Estate for ‘Round 1’ development sites. HOWEVER, the physical environment and the ecology of the Pentland Firth are still not well understood. So in order to get a further understanding of the environmental effects of marine energy devices a better picture of baseline environmental conditions must be done, which includes basic hydrodynamic conditions
- There are many questions related to hydrodynamics which need be solved, as for example: How good is the energy source that we need harness. How is the energy dissipated?. What long term and far-field effects could have the MRE devices installation? And these questions require research at several work areas. There are uncertainty in forcing, which could be the changes in tidal forcing and hydrographical regimen? There are uncertainty in Underlying processes: there are different scales of resolution, hydrodynamics is a 3D process, we need have a further understanding of turbulence, friction coefficient, sediment transport, etc, etc. And there are also uncertainty in far-field effects, could the MRE devices installation affect shoreline morphodynamics or nutrients transport?
- So, theoretical models arises as an indispensable tool to get a better understanding of physical process. Numerical models play an important role in both MRE development and MRE environmental impacts research, because Developers need to know how much energy is available in relation to initial site selection Before we would be capable of predict effects of installation of ME converters we have to know how the energy is dissipated. Numerical models are a monitoring tool more time and cost efficient than punctual measures They cover several scales both temporal and spatially From the ecological point of view it’s important have a prediction tool, which could be coupled to ecological numerical models to evaluate temporal and spatial consequences Using hydrodynamic numerical models is possible generating accurate predictions of nutrients and sediment transport in coastal waters.
- In ICIT we are using the SUNTANS model because of a collaboration between Institute of Petroleum Engineering of Heriot Watt University and Stanford University. SUNTANS stands for Stanford Unstructured Nonhydrostatic Terrain-following Adaptive Navier-Stokes Simulator. It is a numerical model designed for the simulation of complex, non-hydrostatic coastal, river and estuarine flows with high resolution on unstructured grids using parallel computers
- SUNTANS solves the ocean equations. That is, the three-dimensional, Navier-Stokes equations under incompressibility and Boussinesq approximations, with a large-eddy simulation of the resolved motions (/mousions/). (These approximations are necessary to the equations could be solved easier.)
- Main advantages of Suntans model are that it is an open source available for academic and research purposes It is tridimensional the unstructured grid provides exceptional resolution around fine-scales features Parallel implementation facilitates high resolution And it includes the non-hydrostatic approximation.
- Most of hydrodynamic models adopt the hydrostatic approximation. It is a simplification of the equation governing the vertical component of velocity. This means that pressure at any point in the ocean is due to the weight of the water above it. When the hydrostatic approximation is applied the acceleration and the (di) eddy viscosity terms for the vertical velocity component (compóunent) are assumed to be much smaller than the gravitational acceleration term, and therefore it can be neglected (niglectid). When a fluid is in motion, the vertical pressure gradient is also influenced by the vertical acceleration and friction, and the pressure is result of adding the static and dynamic pressure. SUNTANS can solve the non-hydrostatic component of pressure, which is important in high latitudes because of probably existence of bottom density currents (/carrents/) and in sill regions as fjords and inlets because are potential super critical flows areas. Therefore, this model is particularly suitable for application to the 3D spatial wave/current problem of highly active tidal energy sites.
- Currently SUNTANS is installed on the Heriot-Watt University Cluster. It is presently modeling tidal currents for the Pentland Firth in the first instance. In these pictures you can see some of the grids that we have done. First of them just cover the PF area and Swona and Stroma are not included. In the second one we have considered the islands but there are not flux towards Scapa Flow. For this reason we did the third. And the number four is the biggest one, but the computational effort is too high as well.
- Boundary conditions are given by the first eight tidal constituents (M2, S2, N2, K2, K1, O1, P1, Q1) computed by OTIS, which is a tidal global model. The resolution of the data is one over twelve degree. And this is the bathymetry interpolated onto the grid.
- It’s just began. Next work will be calibration using ADCP data, comparison the results with other models (e.g Mike 21), coupling SUNTANS with wave models to study tide-wave interaction, apply to sediment transport and ecological aspects.