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% $Name$ |
% $Name$ |
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\section{Shapiro Filter} |
\section{Shapiro Filter} |
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\label{sect:shapiro-filter} |
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The Shapiro filter (Shapiro 1970, 1975) is a high order horizontal |
The Shapiro filter \cite{Shapiro_70} is a high order horizontal |
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filter that efficiently remove small scale grid noise |
filter that efficiently remove small scale grid noise |
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without affecting the physical structures of a field. |
without affecting the physical structures of a field. |
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It is applied at the end of the time step %(the\_correction\_step), |
It is applied at the end of the time step %(the\_correction\_step), |
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using pure numerical differences and ignoring |
using pure numerical differences and ignoring |
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grid spacing. |
grid spacing. |
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This later form is stable whatever the grid is, and therefore |
This later form is stable whatever the grid is, and therefore |
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specially useful for highly anisotropic grid such as spherical |
specially useful for highly anisotropic grid such as spherical |
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coordinate grid. |
coordinate grid. |
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A damping time-scale parameter $\tau_{shap}$ |
A damping time-scale parameter $\tau_{shap}$ |
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defines the strength of the filter damping. |
defines the strength of the filter damping. |