Input File

An input file used by MOOSE-based applications is a human-readable text file that can be prepared in an ordinary text editor.

Blocks

Every input file will contain blocks with the following format:

[BlockName]
  parameters
[]

where BlockName can contain letters, numbers, and underscores.

Nested Blocks

Some blocks allow nesting; an example of a nested block would look like this:

[BlockName]
  [SubBlock]
    parameters
  []
[]

Parameters

Parameters are specified in the following format:

parameter_name = value

There are several types of values that can be supplied as parameters:

Parameter typeExample valueNote
Integer1
Real3.2
Vector of integers'1 14 6'Note the ' around the values
Vector of reals'1.2 5.4 6.99'Note the ' around the values
Point in 3D space'x y z'x, y and z are real spatial coordinates
BooleanTrue, False, On, Off, 1, 0
String"Text"Note the " around the values

The list of parameters you can specify in each block is given via the type parameter. The type refers to a C++ class which defines its input file parameters. The type of each parameter is specified in the C++ class and is documented in the user manual.

Comments

Comments are supported. They start with # and can be placed almost anywhere in the input file.

[Components]
  # 1 meter long pipe at (0, 0, 1)
  [pipe1]
    type = FlowChannel1Phase
    # geometrical parameters
    position = '0 0 1'
    length = 1.0       # in meters
  []
[]

Named values

It is possible to create named values that can be used thoughout the input file.

radius = 2
commentnote

Note: These values cannot be specified inside blocks that have the type parameter. Usually, these values are specified at the top level of the input file outside of any block. When specified inside a block, they are local to the block.

Expressions

Mathematical operations can be done using the fparse directive:

circumference = ${fparse 2 * pi * radius}

Unit conversion

Simple unit conversion is supported via units directive:

length = ${units 1 in -> m}

Here, length will have the value of 0.0254.

Substitution

To use the named value in an input file, use the ${name} syntax:

len = 1

[Block]
  length = ${len}
[]

Here, the length parameter in Block will have the value of 1.

Global Parameters

Global parameters are parameters that are used globally in the whole input file. They are specified in the [GlobalParams] block:

[GlobalParams]
  A = 1.0
[]

If any block in the input file accepts parameter A, then this value will be used and does not have to supplied individually in every such block.

The global value can be locally overriden inside the block:

[GlobalParams]
  A = 1.0
[]

[Block]
  type = SomeType
  A = 2.0
[]

Example

The following input file shows the above-explained features on a simple input file:

# radius of a flow channel
r = ${units 5 cm -> m}
# cross-sectioanl area
A_pipe = ${fparse pi * r * r}
# hydraulic diameter
D_h_pipe = ${fparse 2 * r}

[GlobalParams]
  initial_p = 1e5   # Pa
  initial_vel = 0   # m/2
  initial_T = 310   # K

  closures = simple
  rdg_slope_reconstruction = full
[]

[FluidProperties]
  [fluid]
    type = IdealGasFluidProperties
  []
[]

[Components]
  [pipe]
    type = FlowChannel1Phase
    position = '0 0 0'
    orientation = '1 0 0'
    length = 2
    A = ${A_pipe}
    D_h = ${D_h_pipe}
    n_elems = 25
    f = 0
    fp = fluid
  []

  [inlet]
    type = InletStagnationPressureTemperature1Phase
    input = 'pipe:in'
    p0 = 1.00001e5
    T0 = 310
  []

  [outlet]
    type = Outlet1Phase
    input = 'pipe:out'
    p = 1e5
  []
[]

[Postprocessors]
  [T_inlet]
    type = SideAverageValue
    boundary = pipe:in
    variable = T
  []
[]

[Preconditioning]
  [pc]
    type = SMP
    full = true
  []
[]

[Executioner]
  type = Transient
  start_time = 0
  end_time = 1
  dt = 0.1

  solve_type = NEWTON
  line_search = basic

  nl_max_its = 5
  nl_rel_tol = 1e-5
[]

[Outputs]
  exodus = true
  csv = true
[]

More Information

The exact blocks and their allowed types will be explained in other sections of this documentation.

Previousarrow_backNextarrow_forward