21. MICROWAVE_HEATING Namelist

This namelist specifies the parameters that manage the computation of the dielectric heat source for microwave heating simulations. It is required whenever the PHYSICS namelist option microwave_heating is enabled. The computation uses the frequency-domain solver for time-harmonic Maxwell’s equations, using the configuration specified by the FDME_SOLVER namelist, to solve an auxiliary electromagnetics (EM) problem. The equations are solved on the tetrahedral mesh specified by the EM_MESH namelist, which is generally different than the mesh used for heat transfer. EM boundary conditions are defined using ELECTROMAGNETIC_BC namelists.

Caution

The electromagnetic models assume SI units by default. In particular, the computed dielectric heat is a power density, W/m3 in SI units. If you want to use a different system of units, you must assign appropriate values to the PHYSICAL_CONSTANTS namelist variables vacuum_permittivity (\(\epsilon_0\)) and vacuum_permeability (\(\mu_0\)).

21.1. Namelist Variables

frequency

The frequency (cycles per unit time).

Type:

real

Default:

none

wg_port_bc

A list of names of “wg-port” type ELECTROMAGNETIC_BC namelists whose power is to be managed by this namelist.

Type:

string list

Default:

none

times

An optional list of one or more heat transfer times \(t_1 < \ldots < t_n\) when the waveguide port feed input powers changes.

Type:

real list

Default:

none

powers

The waveguide input powers. These values are effectively assigned to the EM boundary condition variable power at the appropriate times.

Type:

real array

Default:

None

Notes:

This is formally a 2-dimensional array of values. When times is not specified, the powers are constant in time and are specified as

powers(:,1) = \(p_1, \ldots, p_m\)

or more simply as

powers = \(p_1, \ldots, p_m\)

with one value for each of the \(m\) BC specified by wg_port_bc. When times is specified, additional columns of powers to use at each of those times must also be specified, as in

powers(:,1) = \(p_1, \ldots, p_m\)
powers(:,2) = \(p_1, \ldots, p_m\)
…
powers(:,n+1) = \(p_1, \ldots, p_m\)

prop_change_threshold

This control mechanism determines, at each heat transfer time step, whether the EM heat source is recomputed to account for temperature-dependent changes in the EM material properties. The EM heat source is recomputed whenever the maximum relative difference between the current properties and those from the previous computation exceeds this threshold value. Otherwise the previously computed source is retained. When the properties are independent of temperature, the heat source is recomputed solely when there is a change in the waveguide input powers.

Type:

real

Default:

0.3

Valid Values:

> 0

Notes:

The relevant properties are the (real) magnetic permeability and the real and imaginary parts of the electric permittivity.

data_mapper_kind (experimental)

This specifies the tool used to map fields between the primary heat transfer mesh and the EM mesh. Select “portage” to use an experimental data mapper based on the Portage toolkit, https://laristra.github.io/portage. Otherwise, the standard mapping tool will be used by default.

Type:

string

Default:

“default”

Valid Values:

“default”, “portage”