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SUMMARY:Unstructured meshes and adaptivity for 3D multi-scale ocean modell
 ing - Matthew Piggott\, Imperial College London
DTSTART:20080122T110000Z
DTEND:20080122T120000Z
UID:TALK9406@talks.cam.ac.uk
CONTACT:Deb Shoosmith
DESCRIPTION:Over the past decade there has been growing interest in the us
 e of unstructured mesh based methods in ocean modelling. Moving from struc
 tured to unstructured meshes offers many potential benefits. In particular
  it allows for an excellent representation of complex coastlines and bathy
 metry\, and the ability to use wildly different resolutions in different p
 arts of the domain. For example enhanced resolution may be employed to bet
 ter resolve important localised phenomena such as boundary layer separatio
 ns and overflows\, and also regions of particular socio-economic or scient
 ific importance. Importantly\, unstructured meshes allow for the efficient
  representation of any interaction between a range of coupled spatial scal
 es. Due to their geometric flexibility this can be achieved with unstructu
 red meshes without resorting to the unsatisfactory approach of nesting due
  to the fact that smooth variations in mesh resolution are easily achieved
 .\n\nUnstructured meshes are also the natural framework within which to fo
 rmulate robust adaptive mesh capabilities. Extending the above multi-scale
  ability of the mesh\, adaptive methods can be used to optimally resolve a
 nd track the formation and evolution of localised features in a priori unk
 nown and/or evolving locations. This would be impossible with any fixed me
 sh\, whether unstructured or not.\n\nWhen utilising adaptive algorithms a 
 model is able to automatically allocate computational resources in an opti
 mal and dynamic manner\, as dictated by evolving solution fields and estim
 ates of model and discretisation errors. The aim is that this will lead to
  more efficient calculations\, i.e. overall less mesh nodes would be requi
 red to yield a particular solution to a given accuracy\; also for a given 
 computational resource problems can be solved which are more complex than 
 is currently feasible.\n\nIn this presentation we will describe some of ou
 r experiences with constructing a three-dimensional non-hydrostatic finite
  element ocean model using fully unstructured adaptive mesh techniques. Th
 e model is being developed as an open source community project with the ai
 m of maximising flexibility in terms of what it can simulate without compr
 omising on computational power and novelty.\n\nOf particular importance an
 d focus will be mesh generation\; mesh optimisation operations and mesh an
 isotropy\; error measures\; techniques for accurately describing model sta
 tes close to hydrostatic and geostrophic balance on arbitrary irregular me
 shes\; sharp interface representation\; arbitrary mesh movement\; and load
 -balanced parallelisation. \n\nWith any new modelling approach validation 
 is crucial. Here a range of standard benchmarks will be presented where co
 mparisons with laboratory and other well-validated numerical codes are pos
 sible. Applications and validation against overflow problems\, internal wa
 ves\, flow past bathymetry\, western boundary currents\, basin and global 
 scale tides\, tsunami\, wetting and drying in estuaries\, and baroclinic c
 irculation in the North Atlantic will also be presented. \n\nWe will concl
 ude by highlighting future plans for the model.
LOCATION:British Antarctic Survey\, Room 307
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