Preprocessor tutorial — Conducting Sphere and Bicone

In this tutorial, the aim is to set up the model and settings file in order to generate the input for POLARIS. The model analyzed here is discussed in Sphere and Bicone.

Import and view

To begin with, we open https://www.tailsit.com/polaris_preprocessor and load sphereBicone.mesh under Select mesh file from the share/examples/sphereBicone folder. One should obtain the following views

View of imported mesh and element count

View with wireframe and normals

Note that after loading the file, it is often needed to press Reset View in the top of the window first in order to see the entire model.

Domains

In a first step, one has to define all the physical domains. Here, the sphere is an electrode with prescribed voltage, the bicone a free or floating potential with prescribed charge and they are surround by air. First, we define the air region as a dielectric domain.

Air region

Then, the electrode is specified with \(100\,kV\) as prescribed potential.

Sphere as electrode

And, finally, the bicone is a floating potential without charge.

Bicone as free or floating potential

Once declared, the domains can be stored in a JSON file, see Sphere and Bicone - domains.

Surfaces

The crucial step is now to specify all the surface regions found in the initial mesh file. Here, the logic is to choose which region is on the in- and on the outside of each surface. The displayed normal vectors point from the in- to the outside!

In the given case, both surfaces have nothing on their inside parts that contributes to the problem and, therefore, it is set to Void. The outside of both regions is obviously Air. Finally, one has to decide whether a surface itself is an interface between two materials are assigned to an electrode or floating potential. Here, the choice is obvious and the following setting is made.

Surface declarations

As in the Domains case, the surface constellation can be stored in a JSON file, see Sphere and Bicone - surfaces

Solver

The last settings are related to the parameters of the Fast Multipole Method (FMM), the Boundary Element Method (BEM) quadrature, the tuning of the GMRES solver and the number of computational threads. Note that numThreads: 0 implies that all available threads will be used. The default settings are displayed below.

Solver settings

Again, these settings can be stored in a JSON file, see Sphere and Bicone - solver.

Input data

The final step is to press Generate button in the top part of the window. This generates a settings.yaml file which, together with the mesh file, allows for a run of the polaris executable. Note, that one can also edit or manually generate the above mentioned JSON files and load them into the respective positions in the UI.