ABL Forcing

abl_forcing

abl_forcing allows the user to specify desired velocities and temperatures at different heights. These velocities and temperatures are enforced through the use of source in the momentum and enthalpy equations. The abl_forcing option needs to be specified in the momentum and/or enthalpy source blocks:

- source_terms:
   momentum: abl_forcing
   enthalpy: abl_forcing

This option allows the code to implement source terms in the momentum and/or enthalpy equations. A sample section is shown below

abl_forcing:
  search_method: stk_kdtree
  search_tolerance: 0.0001
  search_expansion_factor: 1.5
  output_frequency: 1

  from_target_part: [fluid_part]

  momentum:
    type: computed
    relaxation_factor: 1.0
    heights: [250.0, 500.0, 750.0]
    target_part_format: "zplane_%06.1f"

    # The velocities at each plane
    # Each list include a time and the velocities for each plane
    # Notice that the total number of elements in each list will be
    # number of planes + 1
    velocity_x:
      - [0.0,      10.0, 5.0, 15.0]
      - [100000.0, 10.0, 5.0, 15.0]

    velocity_y:
      - [0.0,      0.0, 0.0, 0.0]
      - [100000.0, 0.0, 0.0, 0.0]

    velocity_z:
      - [0.0, 0.0, 0.0, 0.0]
      - [100000.0, 0.0, 0.0, 0.0]

  temperature:
    type: computed
    relaxation_factor: 1.0
    heights: [250.0, 500.0, 750.0]
    target_part_format: "zplane_%06.1f"

    temperature:
      - [0.0,      300.0, 280.0, 310.0]
      - [100000.0, 300.0, 280.0, 310.0]

Note

The variables in the abl_forcing subsection are prefixed with abl_forcing.name but only the variable name after the period should appear in the input file.

abl_forcing.search_method

This specifies the search method algorithm within the stk framework. The default option stk_kdtree is recommended.

abl_forcing.search_tolerance

This is the tolerance specified for the search_method algorithm. A default value of 0.0001 is recommended.

abl_forcing.search_expansion_factor

This option is related to the stk search algorithm. A value of 1.5 is recommended.

abl_forcing.output_frequency

This is the frequency at which the source term is written to the output value. A value of 1 means the source term will be written to the output file every time-step.

Note

There are now two options in the following inputs. The can be momentum and/or temperature.

abl_forcing.momentum.computed

This option allows the user to choose if a momentum source is computed from a desired velocity (computed) or if a user defined source term is directly applied into the momentum equation (user_defined).

abl_forcing.momentum.relaxation_factor

This is a relaxation factor which can be used to under/over-relax the momentum source term. The default value is 1.

abl_forcing.momentum.heights

This is a list containing the planes at which the forcing should be implemented. Each input is the height for that plane. This is the naming convention in the mesh file.

abl_forcing.momentum.target_part_format

This is the format in which the planes are saved in the mesh file.

abl_forcing.momentum.velocity_x

A set of lists containing the time in the first element, followed by the desired velocity at each plane in the \(x\) direction.

abl_forcing.momentum.velocity_y

A set of lists containing the time in the first element, followed by the desired velocity at each plane in the \(y\) direction.

abl_forcing.momentum.velocity_z

A set of lists containing the time in the first element, followed by the desired velocity at each plane in the \(z\) direction.

Note

The temperature has the same inputs as the momentum source (abl_forcing.temperature.type, abl_forcing.temperature.relaxation_factor, abl_forcing.temperature.heights, and abl_forcing.temperature.target_part_format) which take the same options.

abl_forcing.temperature.temperature

A set of lists containing the time in the first element, followed by the desired temperature at each plane.