---
name: "gpiv_vorstra"
section: "1"
platform: "linux"
package: "gpivtools"
version: "0.6.0-3.1"
release: "Debian 8 (Jessie)"
platforms: ["linux"]
url: "https://new.carta.tech/gpiv_vorstra"
---

# gpiv\_vorstra(1)

Calculates the differential quantities vorticity, shear strain and normal strain from PIV data.

## NAME

gpiv\_vorstra - Calculates the differential quantities vorticity, shear strain and normal strain from PIV data.

## SYNOPSIS

**gpiv\_vorstra** \[**-d** *N*\]  \[**-h** \| **--help**\]  \[**-n** \| **-o** \| **-s**\] \[**--no\_g** \] \[**-p** \| **--print**\]  \[**-g** \| **--g**\]  \[**-v** \| **--version**\]  \[*filename*\]  \< *stdin* \> *stdout*

## DESCRIPTION

**gpiv\_vorstra** *calculates the differential quantities like* *vorticity, shear strain and normal strain from PIV data. You can* *choose from several differential schemes: central differentiation,* *least squares, Richardson extrapolation and circulation* *method. Circulation method only allows one to calculate vorticity, but no* *strain. The output can be generated as ASCII data containing four* *columns or as GNUPlot Data format that allows one to view/print the data* *as contour plots.*

*The configuration parameters (containing the* **POST** key) may be overruled by the command line options, as explained below.

## Options

- **-d** *N*

  **Differential type to be used: central difference** **(***N*=0), least squares (*N*=1), Richardson interpolation (*N*=2), circulation method (*N*=3)

- **-h** \| **--help**

  On-line help

- **-n**

  Calculate normal strain of the PIV data. As an alternative the program may  be called by its nickname *gpiv\_nstrain*. In combination with  *filename* the output will be written to *filename***.nstr**.

- **-o**

  Calculate vorticity of the PIV data. As an alternative the program may  be called by its nickname *gpiv\_vorty*. In combination with  *filename* the output will be written to *filename***.vor**.

- **-p** \| **--print**

  Print parameters, command line options and eventually used input and output filenames to stdout. The output is identic of *filename***.par**,  in case *filename* is used.

- **-s**

  Calculate shear strain of the PIV data. As an alternative the program may  be called by its nickname *sstrain*. In combination with  *filename* the output will be written to *filename***.sstr**.

- **-g**

  Show contour plot of the output with gnuplot.

- **--no\_g**

  Suppresses to show contour plot of the output with gnuplot.

- **-v** \| **--version**

  Print version information on standard output, then exit successfully.

- *filename*

  Input PIV data file. Overrides stdin and stdout. The output will be written to *filename***.vor** with **-o**, *filename***.nstr**  with **-n** or *filename***.sstr** with **-s**.  Parameters are stored  in *filename***.par** and may be used for future use by including them  in *./gpivrc*.

## SEE ALSO

gpivtools

## AUTHOR

Gerber Van der Graaf