# Boundaries of the study domain

## Introduction

To solve a problem by the finite elements method, the following must be provided:

• the boundaries of the modeled device, i.e. definition of the boundaries or the frontiers of the domain where the field is computed.
• the boundary conditions on the borders, i.e. definition of the values of the state variable (the magnetic potential and the electric potential) on the boundaries of the study domain.

## Boundary conditions with IB

In the majority of the cases, the technique of the infinite box (IB) is used. The boundary conditions are then assigned automatically by Flux on the infinite box (the magnetic potential at infinity is null).

## Boundary conditions without IB

If the technique of the infinite box (IB) is not used, the boundary conditions on the border of the computation domain are set by the user by means of regions known as non-material.

In the absence of the boundary regions, the default boundary condition is applied. The magnetic field is tangent (and the electric field is normal) at the border.

## Symmetries and periodicities

If symmetries are assigned to the study domain, the user should provide the type of the symmetries. Normal magnetic field (and tangential electric field) or tangential magnetic field (and normal electric field) can be imposed on the symmetry planes defined in the geometry context.

If periodicities are assigned to the study domain, the user should provide the type of the periodicities. Cyclic or anti-cyclic conditions can be imposed on the periodicity planes defined in the geometry context.