## 25.14.1 Initializing the Entire Flow Field

Before you start your calculations or patch initial values for selected variables in selected cells (Section  25.14.2) you must initialize the flow field in the entire domain. The Solution Initialization panel (Figure  25.14.1) allows you to set initial values for the flow variables and initialize the solution using these values.

Solve Initialize Initialize...

You can compute the values from information in a specified zone, enter them manually, or have the solver compute average values based on all zones. You can also indicate whether the specified values for velocities are absolute or relative to the velocity in each cell zone. The steps for initialization are as follows:

1.   Set the initial values:

• To initialize the flow field using the values set for a particular zone, select the zone name in the Compute From drop-down list. All values under the Initial Values heading will automatically be computed and updated based on the conditions defined at the selected zone.

• To initialize the flow field using computed average values, select all-zones in the Compute From drop-down list. FLUENT will compute and update the Initial Values based on the conditions defined at all boundary zones.

• If you wish to change one or more of the values, you can enter new values manually in the fields next to the appropriate variables. If you prefer to enter all values manually, you can do so without selecting a zone in the Compute From list.

2.   If your problem involves moving reference frames or sliding meshes , indicate whether the initial velocities are absolute velocities or velocities relative to the motion of each cell zone by selecting Absolute or Relative to Cell Zone under Reference Frame. (If no zone motion occurs in the problem, the two options are equivalent.) The default reference frame for velocity initialization in FLUENT is relative. If the solution in most of your domain is rotating, using the relative option may be better than using the absolute option.

3.   Once you are satisfied with the Initial Values displayed in the panel, you can click the Init button to initialize the flow field. If solution data already exist (i.e., if you have already performed some calculations or initialized the solution), you must confirm that it is OK to overwrite those data.

Saving and Resetting Initial Values

When you initialize the solution by clicking on Init, the initial values will also be saved; should you need to reinitialize the solution later, you will find the correct values in the panel when you reopen it. If you wish to define initial values now, but you are not yet ready to initialize the solution, you can follow the instructions above for setting the values and then click Apply instead of Init. This will save the currently displayed values without initializing the solution. You can return to the panel later on and perform the initialization.

If you accidentally select the wrong zone from the Compute From list or manually set a value incorrectly, you can use the Reset button to reset all fields to their "saved'' values. Values are saved each time the panel is opened, before Compute From is executed, and after Init or Apply is executed.

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