COBALT Interface

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The ICEM CFD - COBALT output interface creates grid and boundary conditions files in accordance with the COBALT file format.

Creating the COBALT Input File

The COBALT output interface can be invoked from the AI*Environment.  Under the menu "Output", "Select solver", select "COBALT".  Then select "Write input".   A window opens to allow the specification of the files to be translated into the COBALT format.  An existing unstructured domain file must first be selected.   In addition, the output interface requires the boundary conditions file and the offset value for patch numbering. It also offers the option to define the name of the COBALT input files, three scaling factors, the file format and the data precision.  Default names for the boundary condition and COBALT files are given.  These can be modified as necessary. The translator adds the suffix ".bc" to the COBALT boundary condition file. The interface generates both the COBALT grid and boundary condition files in the current project directory.

Defining boundary conditions for COBALT

After generating the mesh, and prior to running the translator, boundary conditions for COBALT can be defined using the COBALT Graphical User Interface. Under the menu "Output", "Select solver", select "COBALT". Then click on the "Boundary Conditions" icon. The "Family Boundary Conditions" window opens allowing to set boundary conditions on the mesh families. Six boundary conditions types are available; Farfield, Rotor/Propeller, Sink, Solid Wall, Source and User Specified.

After selecting a boundary condition type, a window opens with options for the chosen type. The following paragraphs give more details on the settings required for each boundary condition type. Note that by default, the boundary condition name is set to the family name.  This can be modified in each boundary condition window.

1. Farfield

• For a "Farfield" boundary condition type, three boundary condition methods are available:
• fixed
• modified Riemann invariants
• original Riemann invariants

In addition, values for the static pressure and temperature, turbulent kinetic energy and omega, Mach number and angles of attack and sideslip must be entered.

2. Sink

• For a "Sink"  boundary condition type,  six boundary condition methods  are available:
• static pressure
• total pressure
• mass flow
• corrected mass flow
• bleed plenum pressure
• area ratio


• Type of performance analysis (for all methods except "bleed plenum pressure") :
• Yes (0)
• Double yes (2)
• Symmetric yes (3)
• No (1)


• If the performance analysis is turn on, the following variables are required:
• Capture area
• Rake center coordinates
• Vector normal to rake

3. Source

• For  a "Source" boundary condition type, two boundary condition methods are available:
• total pressure
• Riemann invariants

 
• Type of performance analysis :
• Yes (0)
• No (1)

• In addition, values for the static pressure and temperature, turbulent kinetic energy and omega, Mach number, axis location and swirl coefficients must be entered.

4. Solid Wall

• For  a "Solid Wall" boundary condition type, four boundary condition methods are available:
• slip
• adiabatic no slip
• isothermal no slip
• the value for the temperature is required.
• general no slip
• the values for the convection heat coefficient, the temperature, the heat flux, the roughness height, the angular velocity, and the location of the rotational axis must be entered.
• For all methods, specify if the forces & moments are to be computed.

5. Rotor/Propeller

• For  a "Rotor/Propeller" boundary condition type, two boundary condition methods are available:
• disk
• annulus
• For both methods, the values for the thrust vector, angular velocity and peak loading position must be supplied.  In addition, the option to output simple parameters may be selected.

6.  User specified

• For a "User specified" boundary condition type, two boundary condition methods are available:
• specified entry
• The values for the velocity, the pressure, the turbulent kinetic energy and omega must be provided.
• coded entry

Please refer to the General Remarks section for more details on how to set boundary conditions.  The boundary condition types are defined with a negative integer. Please refer to the COBALT User's Manual for the complete list of boundary condition types supported by the flow solver.

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