# Stage of positioning

## Introduction

After import of mesh and simplification of geometry, the quality of the faces obtained starting from mesh data can be unsatisfactory for the Flux further operations (see examples below). In this case, it is necessary to adjust the geometry.

- If we want to impose the condition of periodicity on two faces which theoretically form an angle of 60°, but in reality the imported faces form an angle of 59.9999°, it is necessary to adjust the geometry in such way that the real angle between the two faces to be 60°.
- If we want to use the sliding cylinder entity and if the face corresponding to the surface of dissociation not be really carried by a cylindrical surface, it will then be necessary to adapt the consequently geometry.

## Positioning of faces: use

The positioning of the faces is optional but becomes compulsory for the faces in the following cases:

If … | the positioning … |
---|---|

kinematics coupling | of dissociation faces (sliding cylinder, boundary of mobile mechanical set and of compressible mechanical set) |

Symmetry and/or periodicity planes |
of faces located on these planes |

… is compulsory |

## Concept of positioning

We call positioning of a face on a plane or on a cylinder the operation that consists in projecting the face on a reference plane or cylinder, defined by the user.

The positioning is not intended to orient differently the planes with respect to imported geometry, but to homogenize this geometry in order to ensure a good Flux further operation.

## Principle of positioning

The positioning of a face F on a surface S means the projection of points, nodes of F on S, the edges follow the movement. Thus, the use of positioning of faces by their displacement with many degrees with respect to the initial geometry can results in a geometry deformation.

Many successive displacements can emphasize the deformation of the geometry even if we return to an arrangement conform to the imported geometry.