More than one volume mesh can be imported into the same simulation simultaneously using any combination of the allowable formats. The process is the same as when importing a single file using the Open dialog, but using multiple file selections with the Ctrl key depressed. Alternatively, each mesh file can be imported one at a time in a consecutive manner. The result will be the same regardless of which method is used.
This capability is useful if you split up the pre-processing effort into multiple files, or if you want to experiment with different geometries of the same part. For example, if you were evaluating the effect of different wing mirrors on the flow over a car body, the body could be in one mesh file, and several alternative mirror designs in other files. Each simulation would then import the same mesh for the car body, and a different mesh for each mirror.
If the same file is imported twice, two copies of the mesh from that file will be created, resulting in two different region definitions. You may then wish to transform one or both of the meshes so they do not occupy the same space.