An incompressible smoothed particle hydrodynamics (ISPH) wave basin with structure interaction for fully nonlinear and extreme coastal waves

In coastal and offshore engineering, complex, generally highly nonlinear and distorted, wavemotion, which may involve breaking, bore propagation, aeration, structure interaction and violent impact, has remained largely intractable to numerical modelling. Smoothed particle hydrodynamics (SPH) holds great promise since it solves the governing equations in Lagrangian form where each particle represents an interpolation of local fluid quantities that carry flow quantities such as mass, pressure, velocity and move according to their underlying mechanics. SPH is thus a meshless method and possesses some unique advantages over conventional mesh-based approaches; no explicit treatment of the free surface and no computational grid mean that sophisticated meshing is not needed for complex fluid or solid geometries. The method is advancing rapidly, both in fundamental development and in its range of applications. An SPH approach has been developed which is truly incompressible, accurate and virtually noise free but, until recently, numerical instability has been a difficulty. This has been solved by a recent development at Manchester which maintains accuracy, efficiency and relative simplicity. The noise-free aspect is important for fluid/structure interaction since noisy pressures would contaminate forces. The effects of trapped air on impact pressures is also known to be important and surface tension determines the nature of wave breaking. These two effects may be incorporated in SPH. The aim of this project is to make the ISPH method into an attractive engineering tool, with the code able to handle very large numbers of particles, particularly in 3-D, using parallel computing to enable a wide range of applications. This would be undertaken at three levels as: a single-phase incompressible, almost inviscid flow solver; a two-phase water/air solver, with air compressible; a two-phase water/air solver with surface tensionTo this end a 3-D numerical coastal wave basin will be developed with the option of including structures of arbitrary geometry such as sea walls, caissons, wind turbine columns, harbours, ships.

The immediate beneficiaries of the new ISPH methodologies and software generated in the project will be the international academic community. Methods and results will be presented to a particular community including academics and industry known as the SPH European Research Interest Community (SPHERIC) for whom Rogers is a co-founder and webmaster. SPHERIC has been holding annual workshops of increasing popularity since 2006, see SPHERIC url: http://wiki.manchester.ac.uk/spheric. Manchester will host SPHERIC in 2010. There are training days associated with each SPHERIC workshop, based on the open source SPHysics software, resulting from the collaboration of four European Universities and Johns Hopkins in the US. Rogers plays the lead role in this software development, see SPHysics url: http://wiki.manchester.ac.uk/sphysics. The new ISPH software will be added to the SPHysics web site. As well as academic members, the SPHERIC steering committee has representatives from the following companies: VA TECH hydro ANDRITZ, ESI BV and EdF, and the research institutes: INSEAN (the Italian Ship Model Basin) and CSCS (the Swiss National Supercomputing Centre). Manchester is part of the European SPH Initiative (ESPHI) Marie Curie grant with five European partners (details on the SPHERIC web site), including EdF and VA TECH Hydro. Rogers is PI and Stansby is co-I at Manchester. The results of this project will be disseminated through this partnership. A renewal of this grant is planned. Through the ESPHI project there are regular exchange visits and secondments between Manchester, EdF and VA TECH Hydro. In addition Stansby leads the Coastal Inundation Super Work Package of the EPSRC Flood Risk Management Research Consortium with substantial EA support, due to be completed by 2011. SPH is being used for modelling wave overtopping in general applications and for the field measurements at Blackpool funded by the EA. A specific product will be a numerical wave basin for coastal domains including structures. This is potentially of high value for the design sea walls, caissons, harbours, ship moorings, wind turbine columns and marine renewable energy structures: barrages, embayments, turbines or wave devices. These are of strategic importance for coastal protection, LNG supply, green electricity generation, under a backdrop of increasing vulnerability due to climate change and sea level rise. The numerical wave basin will be made available through SPHysics as open-source software. Any specific application developed commercially under licence would be managed by the University IP company UMIP Ltd. For example LNG loading/offloading requires specific input on allowable ship motions which would be additional to general-purpose SPH capability. The strategic importance of such coastal facilities cannot be overstated. It should be noted that the use of SPH is already spreading commercially. To our knowledge the following companies are developing and applying SPH: EdF (spillways), Andritz VATech Hydro (hydro turbines), JBA (flooding), Capita Symonds (Olympic slalom canoe course), ESI BV (crash tests), SEA (ship motion in violent offshore seas).