26.15 Automatic Initialization of the Solution and Case Modification

While running a case manually, you can perform certain activities which may facilitate convergence. These actions may take place before initialization, after initialization and/or at other points during the calculation. The process described in this section allows you to enter text commands at each of these times when a case is run from the Run Calculation task page, Workbench, or in batch. In the Calculation Activities task page, enable Automatically Initialize Solution and Modify Case to automatically modify the case.

Calculation Activities Automatically Initialize Solution and Modify Case Edit...

Figure 26.15.1: The Automatically Initialize Solution and Modify Case Option

When using this option, you can edit the calculation settings. Note that the original settings always exist and cannot be deleted. The duration of the calculation is defined, so immediately after enabling Automatically Initialize Solution and Modify Case, you will notice that the Run Calculation task page will define the case to run with the original settings for a single iteration.

You can now control the number of iterations or time steps for the calculation. When Automatically Initialize Solution and Modify Case option is disabled, you will have to specify the iterations or time steps using the Run Calculation task page.

For an uninitialized case, clicking the Edit... button will display the Automatic Solution Initialization and Case Modification dialog box, which allows you to specify the initialization method and to modify the case.

Figure 26.15.2: The Automatic Solution Initialization and Case Modification Dialog Box

In the Initialization Method tab, you can specify four different initialization methods:

Initialize with Values from the Case   uses the values set in the Solution Initialization task page.

Use Solution Data from File   requires you to read in a data file containing the desired initialization for this case, as shown in Figure  26.15.2.

Use Existing Solution Data   is analogous to changing the values in a case and continuing the calculation. However, the iteration counter will be reset to 0 so that the modifications can be applied. Use this method when no solution data exists, similar to the first run.

Whenever the case is initialized, the iteration count is set to 0.

In the Case Modification tab, you can indicate how long you would like to run with the original settings, then make any modifications to the case settings.

Figure 26.15.3: The Case Modification Tab

If you decide to make no modifications, then the counter in the Defined Modifications box will be set to 0. However, you still have the option to specify settings that you would like to apply before initialization, or you can change your original settings. If Before Initialization is enabled, then you can type the text commands in the Commands field. If Original Settings is enabled, you can type in a text command in the Commands field, and/or specify the Number of Iterations/Time Steps.

If you decide to make modifications to your case, increase the number of Defined Modifications and specify additional commands, as shown in Figure  26.15.3, which illustrates the following:

1.   The mesh will be refined.

2.   The iteration count will be set to 0 (in all situations).

3.   The calculation will run for 100 iterations or until convergence.

4.   The Courant number will be set to 50.

5.   The calculation will continue for 75 iterations or until convergence.

6.   The momentum discretization scheme is set and the Courant number is set.

7.   The calculation continues for 1000 iterations or until convergence.

You can make the above changes sequentially and run your case, or you can specify them all at once. When you have completed making the modifications, click OK. A warning message may appear, prompting you to take specific actions. For example, if the Original Settings field is empty, then you may be warned that the original settings will be lost if the case is saved after the modifications are applied. It will prompt you for a response when asked if you would like to add commands that specify the original settings.

If you specify commands for the Original Settings, they will be applied to the case before the first iteration/time step.

Your actions will be summarized in the Calculation Activities task page, as shown in Figure  26.15.1.

If you disable Automatically Initialize Solution and Modify Case, the settings will be disabled and retained, but will not be applied to the case.

When Automatically Initialize the Solution and Modify the Case is enabled, settings defined in the Run Calculation task page will be ignored. Instead, the Number of Iterations will be defined as Automatic, as shown in Figure  26.15.4.

Figure 26.15.4: The Run Calculation Task Page

Altering the Solution Initialization and Case Modification after Calculating

If you decide to edit the solution initialization and case modification settings and one or more iterations have been calculated, then clicking the Edit... button for the Automatically Initialize Solution and Modify Case option will open the Edit Automatic Initialization and Case Modifications dialog box, as shown in Figure  26.15.5.

Figure 26.15.5: The Edit Automatic Initialization and Case Modifications Dialog Box

If you select the first option, the initialization controls and modifications that have already taken place are disabled, therefore you can edit the case modifications that have yet to take place.

If you select the second option, all controls in the Automatic Solution Initialization and Case Modification dialog box are enabled and therefore, you can modify any of the settings.