# Non-meshed coils (3D)

## Definition

A non-meshed coil is a geometric entity of circular, rectangular or more complex shape that has no correspondence in the regions of the computation domain. This entity is superimposed on the computation domain and has no mesh.

The computation of the magnetic field created by the current distribution is carried out using the Biot and Savart formula in an analytic way (or semi-analytic way).

## Geometric aspect

A non-meshed coil does not contain any points, lines, faces and volumes; it does not belong to the geometry. Thus, this type of coil is neglected during the geometry building and by the mesh generator. We can define this type of source before or after the mesh execution. The main advantage of this coil type is a significant reduction of the number of nodes.

## The available non-meshed coils

The shapes of the coils available in Flux are listed in the table below.

Coil Circular Rectangular Composed
line
surface
volume (rectangular section)
volume (circular section)

Example

with 3 pairs of poles

## Non-meshed coils and symmetries/ periodicities

Reminder: as for the other material regions, for the meshed coils the symmetric and/or periodic parts of the modeled device are taken into account by means of the boundary conditions on the symmetry and/or periodicity planes.

For the non-meshed coils , it is necessary to represent the group of coils inside and outside the study domain. This requirement is imposed so there is an accurate computation of the magnetic field in the study domain

Concretely:

• for the coils placed entirely in the study domain:

Flux automatically creates the coils in accordance with the conditions of symmetry and/or periodicity imposed at the study domain level

• for the coils placed in a symmetry and/or a peridiocity plane:

the user should define the entire coil (the internal part, inside the study domain and the external part, outside this domain)