# 4.3.2. Material Properties

In order to solve the equations specified above, properties of the material(s) which make up the domain must be defined. In Aria, this is accomplished by creating material definitions which are assigned to their corresponding portions of the domain (blocks, surfaces, etc). A material is assigned to a specific mesh element using the following

    # Scope: Sierra
    Begin Finite Element Model The_Mesh
      # Other finite element model commands

      use material Kryptonite for block_1
      use material Kryptonite_surf for surface_1
    End Finite Element Model The_Mesh

See Finite element model for more information on specification of the finite element model.

Material property values are prescribed for unique material names using input line commands within an `Aria Material` command block. The general format of a material property line command is as follows:

    [PROPERTY] = [MODEL] [MODEL ARGS...]

This line populates the `PROPERTY` expression using `MODEL` on blocks for which the given material is assigned (For more details on the expression system employed by Aria, refer to Expression Overview). As a demonstration, consider the following geometry:

      surface_1
    +-----------+
    |  block_1  |
    +-----------+

with materials:

    # Scope: Sierra
    Begin Aria Material Kryptonite
      #! 1)
      Emissivity = constant e=0.7

      Begin Material Phase gas_phase
        Species Names = speciesA speciesB speciesC

        #! 2)
        Density = general_ideal_gas R={Rgas}

        #! 3)
        molecular_weight of speciesA = constant M={MspeciesA}
        molecular_weight of speciesB = constant M={MspeciesB}
        molecular_weight of speciesC = constant M={MspeciesC}

      End Material Phase gas_phase
    End Aria Material Kryptonite

    Begin Aria Material Kryptonite_surf
      #! 4)
      heat transfer coefficient = SCALAR_STRING_FUNCTION \$
         f = "2*Emissivity"
    End Aria Material Kryptonite_surf

This example illustrates the following cases:

1. In the most general declaration, the property `Emissivity` is defined using the `Constant` model with argument `E=0.7`. This will produce the expression `EMISSIVITY` on all blocks which have material `KRYPTONITE` assigned.

2. In multi-phase problems, properties can depend on the phase of material. This line definition declares the `DENSITY` of the `GAS_PHASE` of `KRYPTONITE`, and will produce the expression `GAS_PHASE_DENSITY`.

3. Finally if multiple species are present, the property of individual species can be specified by appending the property with the respective species (i.e. `PROPERTY` = `MOLECULAR_WEIGHT OF SPECIESC`). This will produce an expression `GAS_PHASE_MOLECULAR_WEIGHT_SPECIESC`.

4. Note that children of a part inherent the material properties of their parent (e.g. surfaces inherent properties from their owning block). This means that since `SURFACE_1` is connected to `BLOCK_1`, it will have e.g. `EMISSIVITY` defined via `BLOCK_1`’s material definition. The opposite is NOT true, meaning `BLOCK_1` will NOT have `HEAT_TRANSFER_COEFFICIENT` defined.

The reader is referred to the command reference for a comprehensive list of all possible material property definitions and model options.

Note

Chemical material models solved using the `CHEMEQ` library require an entire set of parameters. In this case those parameters are defined within a `Parameters for CHEMEQ` command block embedded within the `Aria Material` command block. A description of the CHEMEQ related parameters can be found in CHEMEQ Reference.

Note

Some tensor properties which are often isotropic can be defined as a single scalar for efficiency. Individual tensor components can be specified by prepending `TENSOR_` to the property name in the material line definition. Otherwise, the scalar case corresponds to . See Thermal Conductivity vs Tensor Thermal Conductivity for an example of this.