6.8.1 Merging Zones

To simplify the solution process, you may want to merge zones. Merging zones involves combining multiple zones of similar type into a single zone. Setting boundary conditions and postprocessing may be easier after you have merged similar zones.

Zone merging is performed in the Merge Zones dialog box (Figure  6.8.1).

Mesh $\rightarrow$ Merge...

Figure 6.8.1: The Merge Zones Dialog Box

When to Merge Zones

ANSYS FLUENT allows you to merge zones of similar type into a single zone. This is not necessary unless the number of zones becomes prohibitive to efficient setup or postprocessing of the numerical analysis. For example, setting the same boundary condition parameters for a large number of zones can be time-consuming and may introduce inconsistencies. In addition, the postprocessing of the data often involves surfaces generated using the zones. A large number of zones often translates into a large number of surfaces that must be selected for the various display options, such as color contouring. Fortunately, surfaces can also be merged (see Section  28.11), minimizing the negative impact of a large number of zones on postprocessing efficiency.

Although merging zones can be helpful, there may be cases where you will want to retain a larger number of zones. Since the merging process is not fully reversible, a larger number of zones provides more flexibility in imposing boundary conditions. Although a large number of zones can make selection of surfaces for display tedious, it can also provide more choices for rendering the mesh and the flow-field solution. For instance, it can be difficult to render an internal flow-field solution. If the outer domain is composed of several zones, the meshes of subsets of these zones can be plotted along with the solution to provide the relationship between the geometry and solution field.

Using the Merge Zones Dialog Box

The procedure for merging multiple zones of the same type into a single zone is as follows:

1.   Select the zone type in the Multiple Types list. This list contains all the zone types for which there are multiple zones. When you choose a type from this list, the corresponding zones will appear in the Zones of Type list.

2.   Select two or more zones in the Zones of Type list.

3.   Click the Merge button to merge the selected zones.

Remember to save a new case file (and a data file, if data exists).