# fix sph/density/corr command

## Syntax

    fix ID group-ID sph/density/corr style args

- ID, group-ID are documented in fix command
- sph/density/corr = style name of this fix command
- style = shepard
- args = list of arguments for a particular style

    shepard args = every nSteps
      nSteps = determes number of timesteps

## Examples

    fix corr all sph/density/corr shepard every 30

## Description

In general the pressure field in SPH exhibits large oscillations. One approach to overcome this problem is to perform a filter over the density.

The filterstyle shepard is one of the most simple and quick correction. Every nSteps timesteps the following rule is applied:

## Restart, fix_modify, output, run start/stop, minimize info

No information about this fix is written to binary restart files.

None of the fix_modify options are relevant to this fix.

No global scalar or vector or per_atom quantities are stored by this fix for access by various output commands.

No parameter of this fix can be used with the start/stop keywords of the run command.

This fix is not invoked during `energy minimization`.

## Restrictions

> none

## Related commands

pair_style sph/artVisc/tensCorr, fix sph/pressure, fix sph/density/continuity

Default: none

(Liu and Liu, 2003) “Smoothed Particle Hydrodynamics: A Meshfree Particle Method”, G. R. Liu and M. B. Liu, World Scientific, p. 449 (2003).