---
name: "mkgeo_ugrid"
section: "1rheolef"
platform: "linux"
package: "rheolef"
version: "7.2-4"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/mkgeo_ugrid"
---

# mkgeo\_ugrid(1rheolef)

unstructured mesh of a parallelepiped (rheolef-7.2)

## NAME

mkgeo\_ugrid - unstructured mesh of a parallelepiped (rheolef-7.2)

## SYNOPSIS

```
mkgeo_ugrid [options] n
```

## EXAMPLE

```
    mkgeo_ugrid -t 10 > square-10.geo
    geo square-10.geo
```

 The previous command build a triangle based 2d unstructured mesh of the unit square:

## DESCRIPTION

This command is useful when testing programs on simple geometries. Invocation is similar to those of **mkgeo\_grid(1)** . It callsg `gmsh` as unstructured mesh generator. It avoid the preparation of an input file for a mesh generator. The optional *n* argument is an integer that specifies the subdivision in each direction. By default n=10. The mesh files goes on standard output.

The command supports all the possible element types: edges, triangles, rectangles, tetrahedra, prisms and hexahedra. It supports also mixed 2D with triangles and quadrangles: \

```
    mkgeo_ugrid -tq 10 | geo -
```

 and mixed 3D with tetraedra, prisms and/or hexahedra:

```
    mkgeo_ugrid -TP  10 | geo -paraview -
    mkgeo_ugrid -PH  10 | geo -paraview -
    mkgeo_ugrid -TPH 10 | geo -paraview -
```

## ELEMENT TYPE OPTION

`-e`

 1d mesh using edges.

`-t`

 2d mesh using triangles.

`-q`

 2d mesh using quadrangles (rectangles).

`-T`

 3d mesh using tetrahedra.

`-P`

 3d mesh using prisms.

`-H`

 3d mesh using hexahedra.

`-tq`

 2d mesh using both triangles and quadrangles.

`-TP` \
 `-PH` \
 `-TPH`

 3d mixed mesh combining tetrahedra, prisms and/or hexahedra.

## THE GEOMETRY

`-a` *float* \
 `-b` *float* \
 `-c` *float* \
 `-d` *float* \
 `-f` *float* \
 `-g` *float*

 The geometry can be any \[a,b\] segment, \[a,b\]x\[c,d\] rectangle or \[a,b\]x\[c,d\]x\[f,g\] parallelepiped. By default a=c=f=0 and b=d=g=1, thus, the unit boxes are considered.

## BOUNDARY DOMAINS

`-[no]sides`

 The boundary sides are represented by domains: `left`, `right`, `top`, `bottom`, `front` and `back`.

`-[no]boundary`

 This option defines a domain named `boundary` that groups all sides.

## REGIONS

`-[no]region`

 The whole domain is split into two subdomains: `east` and `west`. Also, the separating domain is named `interface` in the mesh. This option is used for testing computations with subdomains (e.g. transmission problem; see **usersguide** ).

## CORNERS

`-[no]corner`

 The corners (four in 2D and eight in 3D) are defined as OD-domains. This could be useful for some special boundary conditions.

## COORDINATE SYSTEM OPTIONS

- `-cartesian` `-rz` `-zr`

   Specifies the coordinate system. The default is `cartesian` while `-rz` and `-zr` denotes some axisymmetric coordinate systems. Recall that most of Rheolef codes are coordinate-system independent and the coordinate system is specified in the geometry file `.geo`.

## THE MESH ORDER

This option is related to curved boundaries. Since boundaries are here flat, this option has no practical effect and is provided for test purpose only.

`-order` *int*

 The polynomial approximation mesh order, as defined by `gmsh`. This option enable a possible curved boundary, when applying a suitable nonlinear transformation to the mesh. Default is order=1.

## IMPLEMENTATION

This documentation has been generated from file main/sbin/mkgeo\_ugrid.sh

## AUTHOR

Pierre  Saramito  \<Pierre.Saramito@imag.fr\>

## COPYRIGHT

Copyright   (C)  2000-2018  Pierre  Saramito  \<Pierre.Saramito@imag.fr\> GPLv3+: GNU GPL version 3 or later  \<http://gnu.org/licenses/gpl.html\>. This  is  free  software:  you  are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.