26. PHYSICS Namelist

The PHYSICS namelist specifies which physics models are active in the simulation. The models are implemented by the four primary physics solvers – fluid flow, heat/species transport, electromagnetics, and solid mechanics – which are weakly coupled using time splitting. A brief overview of the physics solvers follows; see Truchas Physics and Algorithms for more details.

Fluid Flow. The fluid flow physics model simulates multi-material, incompressible flow with interface tracking. A gravitational body force is defined using the body_force_density variable. See the MATERIAL namelist for a description of the material properties required by the fluid flow model.

Heat and Species Transport. The heat and species transport physics model simulates both heat conduction with thermal (view factor) radiation, and solutal species diffusion and thermodiffusion. These (primarily) diffusive transport processes are fully coupled; advection of enthalpy and solutal species are handled by the fluid flow physics solver and incorporated as explicit source terms. Heat transport is enabled using the heat_transport flag, and solves the heat equation

(26.1)\[\frac{\partial H}{\partial T} = \nabla\cdot K \nabla T + Q + Q_\text{adv}\]

with dependent variables temperature \(T\) and volumetric enthalpy density \(H\). The enthalpy density is algebraically related to temperature as \(H=f(T)\) where \(f'(T)=\rho c_p\) is the volumetric heat capacity. See the MATERIAL namelist for a description of the material properties required by the heat equation. The optional volumetric heat source \(Q\) is defined using the THERMAL_SOURCE namelist, and the advected heat \(Q_\text{adv}\) by the flow solver. The boundary conditions on \(T\) are defined using the THERMAL_BC namelists. The initial value of \(T\) is defined by the temperature variable of the BODY namelists. View factor radiation systems which couple to the heat equation are defined using ENCLOSURE_RADIATION namelists. Solutal species transport is enabled using the species_transport flag, which solves the \(n\) coupled equations

(26.2)\[\frac{\partial\phi_i}{\partial t} = \nabla\cdot D_i (\nabla\phi_i~[{}+S_i\nabla T]~) + Q_i + Q_{i,\text{adv}}\]

for species concentrations \(\phi_i\). The number of components \(n\) is defined by number_of_species. The thermodiffusion term in Eq.26.2 is only included when coupled with heat transport. See the MATERIAL namelist for defining the diffusivities \(D_i\) and Soret coefficients \(S_i\). The optional volumetric source \(Q_i\) is defined using the SPECIES_SOURCE namelist. The advected species source \(Q_{i,\text{adv}}\) is computed by the flow solver. Boundary conditions on \(\phi_i\) are defined through the SPECIES_BC namelists. The initial value of the \(\phi_i\) are defined through the conc variable of the BODY namelists.

Induction Heating. The induction heating model solves the heat transport model above with an additional Joule heat source computed by an auxiliary electromagnetics problem defined by the INDUCTION_HEATING namelist that models the eddy currents induced by an external low-frequency magnetic field. It is enabled by the induction_heating flag. See the MATERIAL namelist for a description of the material properties required by the electromagnetics solver.

Microwave Heating. The microwave heating model solves the heat transport model with an additional dielectric heat source computed by an auxiliary microwave-frequency electromagnetics problem defined by the MICROWAVE_HEATING namelist. It is enabled by the microwave_heating flag. See the MATERIAL namelist for a description of the material properties required by the electromagnetics solver.

Solid Mechanics. The solid mechanics physics kernel models small strain elastic deformation of solid material phases, including deformations induced by temperature changes. It is enabled using the solid_mechanics flag. See the MATERIAL namelist for a description of the material properties required by the solid mechanics kernel. Displacement and traction boundary conditions are defined using SM_BC namelists. A gravitational body force may be defined using the body_force_density variable. Parameters which define the plasticity model are defined using the VISCOPLASTIC_MODEL namelist.

Namelist usage

Required/Optional:

Required

Single/Multiple Instances:

Single

26.1. Namelist Variables

body_force_density

A constant force per unit mass, g, that acts throughout material volumes. The net force on a volume is the integral of its density times g over the volume. Typically g is the gravitational acceleration.

Type:

real 3-vector

Default:

(0.0, 0.0, 0.0)

Note:

The fluid flow and solid mechanics models always include this body force.

induction_heating

Enables the simulation of induction heating.

Type:

logical

Default:

false

heat_transport

Enables the simulation of heat conduction, advection, and radiation using the heat/species transport physics solver.

Type:

logical

Default:

false

flow

Enables the simulation of fluid flow.

Type:

logical

Default:

false

materials

A list of materials to include in the simulation. These are material names defined in MATERIAL namelists. The list must include all materials assigned to a region in a BODY namelist, or specified as an inflow_material in a fluid flow boundary condition, but it need not include all materials defined in the input file. Use the reserved name “VOID” to refer to the built-in void pseudo-material.

Type:

string list

Default:

none

microwave_heating

Enables the simulation of microwave heating.

Type:

logical

Default:

false

number_of_species

The number of species components. Required when species_transport is enabled.

Type:

integer

Default:

0

Valid Values:

> 0

solid_mechanics

Enables the calculation of solid material stresses and strains.

Type:

logical

Default:

false

species_transport

Enables the calculation of species diffusion and advection using the heat/species transport physics kernel. The number of species components must be specified using number_of_species.

Type:

logical

Default:

false