23. PHYSICS Namelist
23.1. Overview
The PHYSICS namelist specifies which physics models are active in the simulation. The models are implemented by the four primary physics kernels — fluid flow, heat/species transport, induction heating, and solid mechanics — which are weakly coupled using time splitting. A brief overview of the physics kernels 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 kernel models 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 kernel and incorporated as loosely-coupled source terms. Heat transport is enabled using the Heat_Transport flag, and solves the heat equation
with dependent variables temperature \(T\) and enthalpy density \(H\). The enthalpy density is algebraically related to temperature as \(H=f(T)\) where \(f′(T) =\rho c_p`is the volumetric heat capacity. See the :ref:`MATERIAL<MATERIAL_and_PHASE_Namelists>\) namelist for a description of the material properties required by the heat equation. The optional volumetric heat source \(Q\) is defined through the DS_SOURCE namelist using “temperature” as the equation name. The Joule heating source \(Q_{joule}\) is computed by the induction heating kernel, and the advected heat \(Q_{adv}\) by the flow kernel. The boundary conditions on \(T\) are defined through the THERMAL_BC namelists. The initial value of \(T\) are defined through 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
for species concentrations \(\phi_i\). The number of components \(n\) is defined by Number_of_Species. The thermodiffusion term in [·] 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 through the DS_SOURCE namelist using “concentration i” as the equation name. The advected species source \(Q_{i,adv}\) is computed by the flow kernel. Boundary conditions on \(\phi_i\) are defined through the SPECIES_BC namelists. The initial value of the \(\phi_i\) are defined through the Phi variable of the BODY namelists.
Induction Heating. The induction heating physics kernel solves for the Joule heat that is used as a source in heat transport. It is enabled using the Electromagnetics flag. See the MATERIAL namelist for a description of the material properties required by the electromagnetics solver. The Electromagnetics namelist is used to describe the induction heating problem.
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.