&CELL: SOLIDS: BOX

CENTRE

The location of the centre of gravity of the box.

[No default.]

HALF-LENGTHS

Half the overall dimensions of the box.

[No default.]

DIRECTION

A direction vector that specifies the orientation of the box in space.

The normalisation of the vector is not used. Zero-norm vectors are not acceptable.

[By default, the box is not rotated i.e. the half lengths are assumed to have been measured along x, y and z.]

CHARGE

Charge applied to the surfaces of the box.

The charge is added to the surface charges needed to satisfy the boundary conditions. The box can either be a dielectric or a conductor.

In the process of being implemented - initially, the charge is equally distributed over all surfaces, selection of surface panels is planned to be added later.

Specifying this option implies the use of neBEM to solve the field.

VOLTAGE

Voltage of the box, which is assumed to be conducting.

Specifying this option implies the use of neBEM to solve the field.

FLOATING-CONDUCTOR

The box will assume a uniform voltage common on all its surface panels.

In the process of being implemented.

Specifying this option implies the use of neBEM to solve the field.

EPSILON

Dielectric constant of the box relative to vacuum.

Specifying this option implies the use of neBEM to solve the field.

Type	Representation	Notes
`CONDUCTOR`	`CONDUCTORS-1`	Equivalent to CONDUCTOR-1
`CONDUCTOR-1`	`CONDUCTORS-1`	-
`CONDUCTOR-2`	`CONDUCTORS-2`	-
`CONDUCTOR-3`	`CONDUCTORS-3`	-
`DIELECTRICUM`	`DIELECTRICA-1`	Equivalent to DIELECTRICUM-1
`DIELECTRICUM-1`	`DIELECTRICA-1`	-
`DIELECTRICUM-2`	`DIELECTRICA-2`	-
`DIELECTRICUM-3`	`DIELECTRICA-3`	-

label

A one character identification of the solid.

This label serves the same purpose as the wire label for wires, namely the selection of the solid as a place where signals can be measured, around which isochrons are drawn etc.

[By default, no label is assigned.]

discretisation

The approximate linear size of the elements you would like neBEM to use when discretising.

Garfield generates, for each solid, a set of flat panels that together cover the faces. These panels, arbitrary convex polygons, are sub-divided when isolating contact areas between solids and also in order to comply with the neBEM requirement that it be given only rectangles and right-angled triangles. The triangles and rectangles handed to neBEM are called "primitives".

For reasons of accuracy neBEM as a rule sub-divides the primitives into "elements", in a process called "discretisation". The sub-divisions of the primitives are called "elements".

Discretisation will perhaps eventually be automated, but for the time being this remains the responsability of the user. In neBEM, the level of discretisation requested is described by 2 integers: the number of elements that is to be generated along each of 2 sides adjacent to a right angle. Since the shape, orientation and size of the primitives are non-trivial to predict, the level of discretisation is specified on the Garfield side as the desired length of the sides of the elements.

The designation of the surfaces is as follows:

front: the +x face of the box;
back: the -x face of the box;
right: the +y face of the box;
left: the -y face of the box;
top: the +z face of the box;
bottom: the -z face of the box;

All references to coordinates concern the situation before the solid is rotated in place.

The discretisation length can be set in several ways, see Example\ 4 for the SOLIDS command:

by setting a default discretisation length to be used for all solids, by means of the TARGET-ELEMENT-SIZE keyword of a NEBEM command issued before the SOLIDS command;
collectively for all faces of a single solid, e.g. DISCRETISATION=0.1, this overrides the default used for all solids;
individually for one or more faces of the solid, e.g. TOP-DISCRETISATION=0.2, this overrides any previous collective setting;
by setting the discretisation length of a face to AUTOMATIC; if this face is in partial contact, then the discretisation length of the other face will be used, if it has been set; if not, and also in the absence of contact, the TARGET-ELEMENT-SIZE will be used that is in effect when leaving the cell section.

Discretisation lengths have to be given in cm.

[Default: the TARGET-ELEMENT-SIZE that is in effect at the time the solids are read.]

Go to the top level, to &CELL, to SOLIDS, to BOX, to the topic index, to the table of contents, or to the full text.

Formatted on 21/01/18 at 16:55.