Changeset 5566 for anuga_core

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Timestamp:
Jul 24, 2008, 11:07:34 AM (15 years ago)
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anuga_core
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 r5555 \noindent \anuga\index{\anuga} is a hydrodynamic modelling tool that allows users to model realistic flow problems in complex geometries. allows users to model realistic flow problems in complex 2D geometries. Examples include dam breaks or the effects of natural hazards such as riverine flooding, storm surges and tsunami. cells, the topography and bathymetry, frictional resistance, initial values for water level (called \emph{stage}\index{stage} within \anuga), boundary conditions and forces such as windstress or pressure gradients if applicable. boundary conditions and forces such as rainfall, stream flows, windstress or pressure gradients if applicable. \anuga tracks the evolution of water depth and horizontal momentum As such it cannot resolve vertical convection and consequently not breaking waves or 3D turbulence (e.g.\ vorticity). \item The surface is assumed to be open, e.g. \anuga cannot model flow under ceilings or in pipes %\item The surface is assumed to be open, e.g. \anuga cannot model %flow under ceilings or in pipes \item All spatial coordinates are assumed to be UTM (meters). As such, ANUGA is unsuitable for modelling flows in areas larger than one UTM zone (6 degrees wide). \item Fluid is assumed to be inviscid \item Fluid is assumed to be inviscid - i.e.\ no kinematic viscosity included. \item The finite volume is a very robust and flexible numerical technique, but it is not the fastest method around. If the geometry is sufficiently \item Frictional resistance is implemented using Manning's formula, but \anuga has not yet been fully validated in regard to bottom roughness \item ANUGA contains no tsunami-genic functionality relating to earthquakes. %\item ANUGA contains no tsunami-genic functionality relating to %earthquakes. \end{itemize} This section is designed to assist the reader to get started with \anuga by working through some examples. Two examples are discussed; the first is a simple example to illustrate many of the ideas, and the first is a simple example to illustrate many of the concepts, and the second is a more realistic example. \end{itemize} Note specifying both center, radius and polygon will cause an exception to be thrown. Moreover, if the specified polygon or circle does not lie fully within the mesh boundary an Exception will be thrown. \bigskip Module: \module{shallow\_water.shallow\_water\_domain} This is a general class for infiltration and abstraction of water according to a given rate of change. This is a general class for inflow and abstraction of water according to a given rate of change. This class will always modify the \code{stage} quantity. \end{itemize} The user can specify different culvert routines. Hower ANUGA currently specifies one, namely the \code{boyd\_generalised\_culvert\_model} as used in the example below. The user can specify different culvert routines. Hower ANUGA currently provides only one, namely the \code{boyd\_generalised\_culvert\_model} as used in the example below. \bigskip Module: \module{shallow\_water.data\_manager} Obtain flow $[m^2]$ perpendicular to specified cross section. Obtain flow $[m^3/s]$ perpendicular to specified cross section. Inputs: \subsection{DEM Format} A DEM file is a NetCDF representation of regular DEM data. A DEM file in \ANUGA is a NetCDF representation of regular DEM data. \] in which $\eta$ is the Manning resistance coefficient. The model does not currently include consideration of kinematic viscosity. As demonstrated in our papers, \cite{ZR1999,nielsen2005} these equations provide an excellent model of flows associated with inundation such as dam breaks and tsunamis. equations and their implementation in \ANUGA provide a reliable model of general flows associated with inundation such as dam breaks and tsunamis. \section{Finite Volume Method} If no value is specified, the default attribute is taken to be the first one. Note that the Geospatial\_data object currently reads entire datasets into memory i.e.\ no memomry blocking takes place. For this we refer to the set\_quantity method which will read .pts and .csv files into \ANUGA using memory blocking allowing large files to be used. \end{classdesc} \label{mod:neighbourmesh} \section{\module{abstract\_2d\_finite\_volumes.domain} --- Generic module for 2D triangular domains for finite-volume computations of conservation laws} \section{\module{abstract\_2d\_finite\_volumes.domain}} Generic module for 2D triangular domains for finite-volume computations of conservation laws \declaremodule{}{domain} \label{mod:domain} \section{\module{shallow\_water} --- 2D triangular domains for finite-volume computations of the shallow water wave equation. This module contains a specialisation of class Domain from module domain.py consisting of methods specific to the Shallow Water \section{\module{shallow\_water}} 2D triangular domains for finite-volume computations of the shallow water wave equation. This module contains a specialisation of class Domain from module domain.py consisting of methods specific to the Shallow Water Wave Equation } \declaremodule[shallowwater]{}{shallow\_water} \label{mod:shallowwater} quantities \code{stage}, \code{xmomentum} and \code{ymomentum} at a given point in time and space as a triplet. To access e.g.\ \code{stage} one must specify element 0 of the triplet returned by file\_function. triplet returned by file\_function, to access \code{xmomentum} one must specify element 1 of the triplet etc. \subsubsection{Which diagnostics are available to troubleshoot a simulation?} data is often sparse, or non-existent. Note that onshore DEMS can be much finer as the underlying datasets from which they are created often contain several datapoints per m$^2$. It may be necessary to thin out the data so that it can be imported without exceeding available memory. One tool available on the net is called 'decimate'. %FIXME: (Need reference?). \subsubsection{What sort of mesh resolution should I use?} The mesh resolution should be commensurate with your DEM - it does not make sense to put in place a mesh which is finer than your DEM. As an example, if your DEM is on a 25m grid, then the cell resolution should be of the order of 315$m^2$ (this represents half the area of the square grid). Ideally, you need a fine mesh over regions where the DEM changes rapidly, and other areas of significant interest, such as the coast. If meshes are too coarse, discretisation errors in both stage and momentum may lead to unphysical results. All studies should include sensitivity and convergence studies based on different resolutions. If meshes are too coarse, discretisation errors in both stage and momentum may lead to unrealistic results. All studies should include sensitivity and convergence studies based on different resolutions.