# GfsEventFilter

### From Gerris

GfsEventFilter applies "exponential" filtering to a given variable.

The syntax in parameter files is as follows:

[ GfsEvent ] V TSCALE

where `V`

is a variable and `TSCALE`

is a strictly positive number. At every realisation of the event, variable `V`

is replaced by `(1 - a)*V + a*VF`

, where `a = dt/TSCALE`

, `dt`

is the timestep and `VF`

is the filtered variable obtained by corner-value averaging.

### Examples

EventFilter { istep = 1 } U 4

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EventFilter { istep = 1 } V 4

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EventFilter { istep = 1 } U 4

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EventFilter { istep = 1 } V 4

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