Streamer Criterion: Mesh advices

Introduction

The mesh quality has a considerable impact on the results.

In fact, it has an effect on:

• The electric field results quality
• The integration discretization quoted in the previous section. In fact, the discretization path selected by default is based on the mesh elements size.

But, a very fine mesh will involve relatively long computation time.

Depending on the studied devices geometries, the optimal mesh won't be the same.

This section presents some mesh advices for simple cases.

General approach

Given that the computation is based on the mesh elements size, it is essential to discretize enough the Streamers area (it is not possible to postprocess a computation done in an area with two or three mesh layers).

In a general way, it is advised to assign local mesh information (meshpoint, meshlines, etc.) on the geometric entities of the studied area.

In fact, in most of cases, the aided mesh or the adaptive solving will not discretize enough this area.

So the advised approach is to:

• Mesh (with aided mesh activated by default)
• Modify the aided mesh options (deviation, relaxation) and mesh
• Assign local mesh information on the studied area and mesh
  Important: it is strongly advised to generate second order elements . It changes entirely the results quality and it is not much longer to compute.

3D devices

Concerning the 3D devices, in some cases, the computation can be long with a mesh suited for Streamer computation. It is especially the case when the conductors have complex geometry shapes.

The advices are to:

• Choose a potential difference applied in the project which is not much higher/lower than the Streamer inception voltage (for more information, see the Using advices and remarks part)
• Use symmetries or periodicities when it is possible