# 7.16.2.1. Initial Condition

Scope

  Aria Region

Summary

  Allows the specification of a user-defined initial conditions on any combination of volumes, surfaces and nodes.

Description

  There are three methods for setting the initial conditions of the thermal model. The temperature specification must be of exactly one type: e.g., constant, defined in a user subroutine, or read from a solution database file. If a user subroutine is used, real and integer data may be declared that will be local in scope to this instance of the boundary condition. This data may be accessed using a user query function.

    begin Initial Condition BlockName

       Add Surface PartList...

       Add Volume PartList...

       All Volumes

       Node Subroutine {=} Name

       Temperature {=} t0

       Use Data Block Name

       Use File Variable File_variable_name For Aria_variable_name [{of} SpeciesName  | {in} MaterialPhaseName] [ At Time Value  ]

    end Initial Condition BlockName

## 7.16.2.1.1. Line Commands

###### Add Surface

Syntax

  Add Surface PartList…

Summary

  Surface name to which this initial condition applies. May specify a space-delimited list.

Parameter | Value | Default
--- | --- | ---
PartList | string… | –

###### Add Volume

Syntax

  Add Volume PartList…

Summary

  Block names to which this initial condition applies. May specify a space-delimited list.

Parameter | Value | Default
--- | --- | ---
PartList | string… | –

###### All Volumes

Syntax

  All Volumes

Summary

  Apply this command block to all volumes in the mesh file.

###### Node Subroutine

Syntax

  Node Subroutine {=} Name

Summary

  Specifies that the named user-defined subroutine be used. At most one subroutine name may be specified for a given quantity. This subroutine must conform to the “node signature” argument list type.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
Name | string | –

###### Temperature

Syntax

  Temperature {=} t0

Summary

  Set the initial temperature to a constant value.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
t0 | real | –

###### Use Data Block

Syntax

  Use Data Block Name

Summary

  Reference to predefined data to be used by the user subroutine. These values may be changed by the user subroutine.

Parameter | Value | Default
--- | --- | ---
Name | string | –

###### Use File Variable

Syntax

  Use File Variable File_variable_name For Aria_variable_name [{of} SpeciesName | {in} MaterialPhaseName] [ At Time Value ]

Summary

  Assign file nodal variable to valid registered nodal variable for initial condition.

Description

  This line command specifies that the named Aria variable be initialized from a variable contained in the mesh file that is assigned to the region. For example, this line command may be used to initialize a transient calculation from a previously performed steady-state calculation in the following way. Perform the steady-state calculation and output the temperature. Then copy that output file and use it as a mesh file for the transient calculation. Finally, use this line command to tie the variable named `file_variable_name` in the mesh file to the aria variable named `aria_variable_name`. Here `aria_variable_name` must be set to `nonlinear_solution->temperature`.

  The closest time step to the time value found the IO database will be used for the assignment. For an initial condition taken from a steady state results file, omit the optional time command. The optional command is necessary if the initial condition is coming from a file with multiple timesteps.

  Note

  1. Current framework services do not allow restricting this initialization by mesh subset. e.g., if you want to initialize the temperature, then all nodes in the mesh will be initialized.

  2. This command line syntax only supports initialization of temperature field. This restriction may be removed in the future so that chemistry variables or user-defined variables may also be initialized.

  3. Sierra Mechanics uses a DOF naming convention which distinguishes vector fields from scalar fields using an underscore plus component notation (e.g. `field_variable_base_name_1`, `field_variable_base_name_X`). Hence use of external scalar field variable names that include an indexed notation will require that the file variable be renamed in order to be processed correctly as a scalar field in the `IC READ_FILE` setup.

Parameter | Value | Default
--- | --- | ---
File_variable_name | string | –
Aria_variable_name | string | –
{of} | {of | species} | –
SpeciesName | string | –
{in} | {in | material_phase} | –
MaterialPhaseName | string | –