ComputationalGeometry
ComputationalGeometry is the class that implements geometries in chombo-discharge.
In principle, geometries consist of electrodes and dielectrics but there are many problems where the actual nature of the EB is irrelevant (such as fluid flow).
ComputationalGeometry is not an abstract class.
The default implementation is an empty geometry – i.e. a geometry without any objects, but several geometries are included in $DISCHARGE_HOME/Geometries.
Making a non-empty ComputationalGeometry class requires that you inherit from ComputationalGeometry and instantiate the following class members:
Real m_eps0;
Vector<Electrode> m_electrodes;
Vector<Dielectric> m_dielectrics;
Here, m_eps0 is the relative gas permittivity, m_electrodes are the electrodes for the geometry and m_dielectrics are the dielectrics for the geometry.
These are described in detail further down.
When geometries are created, the ComputationalGeometry class will first create the (approximations to the) signed distance functions that describe two possible material phases (gas and solid).
Here, the solid phase is the part of the computational domain inside the dielectrics, while the gas phase is the part of the computational domain that is outside both the electrodes and the dielectrics.
Electrode
The Electrode class is responsible for describing an electrode and potentially also its boundary condition.
Internally, this class is lightweight and consists only of a tuple that holds a level-set function and an associated boolean value that tells whether or not the level-set function is at a live voltage or not.
The constructor for the electrode class is:
Electrode(RefCountedPtr<BaseIF> a_baseIF, bool a_live, Real a_fraction = 1.0);
where the a_baseIF argument is the level-set function and the a_live argument is used by some solvers in order to determine if the electrode is at a live voltage or not.
If a_live is set to false, FieldSolver will fetch this value and determine that the electrode is at ground.
Otherwise, if a_live is set to true then FieldSolver will determine that the electrode is at live voltage, and the a_fraction argument is an optional argument that allows the user to set the potential to a specified fraction of the live voltage.
Dielectric
The Dielectric class describes a dielectric.
This class is lightweight and consists of a tuple that holds a level-set function and the associated permittivity.
The constructors are
Dielectric(RefCountedPtr<BaseIF> a_baseIF, Real a_permittivity);
Dielectric(RefCountedPtr<BaseIF> a_baseIF, Real (*a_permittivity)(const RealVect a_pos);
where the a_baseIF argument is the level-set function and the second argument sets a the permittivity.
The permittivity can be set to a constant (first constructor) or to a spatially varying value (second constructor).
Retrieving parts
It is possible to retrieve the implicit functions for the electrodes and dielectrics through the following member functions:
const Vector<Dielectric>& getDielectrics() const;
const Vector<Electrode>& getElectrodes() const;
Retrieving implicit functions
When generating the geometry we compute the implicit functions for each phase, the gas-phase and the dielectric-phase. If none of the implicit functions for the electrodes/dielectrics overlap, the resulting function will also be a signed distance function. Note that these functions are the unions/intersections of all electrodes and dielectrics.
To retrive the implicit function corresponding to a particular phase, use
const RefCountedPtr<BaseIF>& getImplicitFunction(const phase::which_phase a_phase) const;
where a_phase will be phase::gas or phase::solid.