Thermal initial conditions

The thermal analysis needs only initial temperature values. The temperature that you specify in the Temperature Value box is applied to the entire thermal model.

For steady state analysis, the solver uses Temperature Value to launch the iterative solution process. The temperature that you specify will not affect the final results, but can greatly influence solution time. By starting the iterative solve with a good guess as to the final element temperatures, you can dramatically reduce the number of iterations required to reach convergence, particularly for large, non-linear models.

For a transient analysis, initial conditions are usually specified since they represent element temperatures at time zero. This is the state from which the model evolves. Thus, results will differ depending on initial conditions, especially those obtained near the beginning of the analysis.

In addition to the Temperature Value defined in the Solution dialog box, which sets temperatures for the whole model, you can also define temperatures for elements related to specific geometry by creating an Initial Temperature type Initial Conditions constraint. See Initial Conditions for more information.

Initial Temperature type Initial Conditions constraints only have an effect with the Automatic or Uniform options. They are ignored when used in conjunction with the From File (TEMPF format) or From Results in Other Directory options.

• AutomaticFor a new analysis, the thermal solver uses the fluid temperature that you specify on the Ambient Conditions page, except for elements that have been defined as an Initial Temperature constraint. For a restart, the solver checks if a TEMPF file exists in the specified Restart Files Location and uses it to define initial temperature distribution (except for elements included in an Initial Temperature constraint). If you are restarting a transient analysis and the TEMPF file contains transient results, the results closest to the specified Start Time are used.

• UniformSpecifies a uniform value which the thermal solver applies throughout the model except for geometry for which Initial Temperature constraints are defined.

• From Results In Other DirectoryMaps the elemental temperatures from a source model in another directory onto the elements of the current model. In the specified other directory, you need to have the following files:TEMPFContains the elemental temperatures on the source model.INPFContains input information, including units information, from the source model. The solve-time units must be the same for both analyses. You specify these units on the Solution Units page in the Solution dialog box.tmggeom.datContains the geometry of the source model.You can choose any time step for the initial temperature distribution that is available in the TEMPF file of the source model. It does not need to be the start time for the current solution.If you do a restart using this option, the software ignores the TEMPF file in the specified restart directory, and initializes the distribution using the TEMPF file in your specified other directory. The solver still needs solution files in the specified restart directory to restart the analysis. If the run directory is empty, the software cancels the restart.Note: Do not select your current run directory when using the From Results in Other Directory option, as the TEMPF file will be overwritten before it can be used.Make sure that the necessary files that you want to use from a Simcenter 3D Multiphysics coupled analysis are not in a zipped folder. The software does not automatically unzip the folder.

• Thermal Temperature File (TEMPF format)Specifies the TEMPF file containing the initial temperatures. Use this option to specify a specific file rather than a directory. The file must conform to the TEMPF format and must contain temperatures with the same units as the current analysis. If the file is in the current run directory and is not named TEMPF it is read to initialize the temperature and will not be deleted at the end of the analysis. Initial Temperature entities defined in the model are ignored.You can choose any time step for the initial temperature distribution that is available in the specified TEMPF file. It does not need to be the start time for the current solution.

• Perform Steady State SolutionInstructs the solver to first perform a steady state analysis of the model, then immediately launch the transient analysis, using the steady state values obtained. If you have transient thermal loads defined in the model, you must specify how the solver should handle them by choosing and completing one of the three options for Transient Thermal Loads to Use for Steady State Initial Conditions:At Specified TimeExtracts the boundary condition values for the time case you specify, and uses them as constant values. Type the time case in the Initial Conditions Use Loads at Time box. For a model with constant boundary conditions, use a time value of 0.Average over TimeComputes the time average of all element heat loads and uses them as steady-state boundary conditions. This is useful when the heat loads are periodic.Do Not Use Transient LoadsIgnores all defined time-varying boundary conditions for the steady-state analysis

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