source: anuga_work/production/dampier_2006/report/computational_setup.tex @ 3955

To set up a model for the tsunami scenario, a study area is first 
determined. Here, we define the study area to cover around km of coastline
and extending offshore to around the 70m depth contour. Onshore data covers the
area of interest to CIPMA. The study area is around 6250 km$^2$.

The finite volume technique relies on the construction of a triangular mesh which covers the study region. 
This mesh can be altered to suit the needs of the scenario in question. The mesh can be refined in areas of 
interest, particularly in the coastal region where complex behaviour is likely to occur. For the purpose
of this study for CIPMA, we will refine the mesh around the major onshore gas facility and the gas pipelines.
In setting up the model, the user defines the area of the triangular cells in each region of interest\footnote{Note that the cell 
area will be the maximum cell area within the defined region and that each 
cell in the region does not necessarily have the same area.}.
The cell areas should not be too small as this will cause unrealisticly long computational time, 
and not too great as this may inadequately capture important behaviour. 
%There are no gains in choosing the area to be less than the supporting data.
Figure \ref{fig:dampier_area} shows the study area with regions of difference cell areas. The total number
of cells is . 
Lateral accuracy refers to the distance at which we are confident in stating a region is inundated. 
Figure \ref{fig:dampier_area} shows the maximum triangular cell area and lateral accuracy for each region. 
Therefore we can only be confident in the calculated inundation extent surrounding the onshore
gas infrastructure to within 30 m.


\begin{figure}[hbt]

  %\centerline{ \includegraphics[scale=0.15]{../report_figures/dampier_resolution_zones.jpg}}

  \caption{Study area for Dampier scenario highlighting four regions of increased refinement.
Region 1: Surrounds onshore gas infrastructure at Dampier with a cell area of 500 m$^2$ (lateral accuracy 30 m).
Region 2: Surrounds the gas pipelines with a cell area of 5000 m$^2$ (lateral accuracy 100 m).
Region 3: The remaining area is given a cell area of 100000 m$^2$ (lateral accuracy 450 m).
}
  \label{fig:dampier_area}
\end{figure}


The final item to be addressed to complete the model setup is the 
definition of the boundary condition. As 
discussed in Section \ref{sec:methodology}, a Mw 9 event provides
the tsunami source. The resultant tsunami wave is made up of a series
of waves with different amplitudes which is affected by the energy
and style of the event as well as the bathymetry whilst it travels
from its source to Dampier. The amplitude and velocity of each of these
waves are then provided to ANUGA as boundary conditions and propagated
inshore.