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%% $Header: /u/gcmpack/MITgcm/pkg/generic_advdiff/gad_advection.tex,v 1.2 2004/04/01 04:23:33 edhill Exp $ |
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%% $Name: $ |
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\chapter{Generic Advection Diffusion Package} |
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Package ``generic\_advdiff'' provides a common set of routines for |
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calculating advective/diffusive fluxes for tracers (cell centered |
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quantities on a C-grid). |
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Many different advection schemes are available: the standard centered |
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second order, centered fourth order and upwind biased third order |
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schemes are known as linear methods and require some stable |
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time-stepping method such as Adams-Bashforth. Alternatives such as |
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flux-limited schemes are stable in the forward sense and are best |
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combined with the multi-dimensional method provided in gad\_advection. |
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There are two high-level routines: |
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\begin{itemize} |
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\item{GAD\_CALC\_RHS} calculates all fluxes at time level ``n'' and is |
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used for the standard linear schemes. This must be used in |
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conjuction with Adams--Bashforth time stepping. Diffusive and |
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parameterized fluxes are always calculated here. |
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\item{GAD\_ADVECTION} calculates just the advective fluxes using the |
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non-linear schemes and can not be used in conjuction with |
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Adams--Bashforth time stepping. |
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\end{itemize} |
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