This is one of the most potentially confusing and cumbersome ANSYS concepts.
Before you can do something in ANSYS, you usually need to tell ANSYS what to do it to. We discussed "picking" in the last section. Picking can be tricky, particularly among a large number of entities. "Selecting" can aid in the picking procedure.
Selecting is based on the concept that ANSYS can "forget about" some of the entities. By default, "Everything" is "Selected"--i.e. ANSYS "knows about" all entities. If you only want to work with part of the model, you can select those parts. ANSYS will temporarily "forget about" entities other than the ones you select. If you select half your model and run commands like mpchg,1,all, only that selected half of the model will be affected, despite the all option in the command. For ANSYS, the part that is currently selected is all that exists at the moment.
The two most important options under Select in the menu above are Entities and Everything. I haven't even used the other two.
Everything does what it means. EVERYTHING is selected, ANSYS "remembers" the ENTIRE model and all entities. The Everything option should be used after you're done working with one selected part of the model to "remind" ANSYS about the rest of it so you can continue working with other parts.
Selecting Entities brings up its own window, pictured at the right.
The first box allows specify which type of entity you'd like to select, nodes, elements, volumes, areas, lines, or keypoints.
The second box specifies how you'd like to select them. The only options I've used are By Num/Pick and Attached to.
By Num/Pick should be obvious, we just spent the last section talking about picking. As an example, create a couple areas. Under the Plot menu, select Areas. Select Entities, Areas By Num/Pick. Click OK and pick the first area. Under the Plot menu, choose Replot. All areas but area 1 dissappear. ANSYS only knows about the area you selected. You can only affect area 1. Now Select Everything and Replot again. All areas are now displayed and can be worked with.
Attached to has its own unique uses. Mesh the areas you created for the example above. Select just area 1 as above. Plot Areas. Areas 2 and above are gone. Now Plot Elements. You see all the elements from all the areas. Although you selected area 1 and told ANSYS to forget about the other areas, ANSYS still "sees" all the lines and nodes and elements that make up your model. Now, go the the Select Entities menu and select Elements Attached to. The Select window changes a bit and gives you a different set of options. Select Areas From Full. We are going to select those ELEMENTS which are ATTACHED TO all the AREAS (from full). However, since we previously selected area 1, ANSYS still only knows about area 1 for now, and selecting the elements attached to the current "full" set of areas simply selects the elements of area 1. Click OK and Plot Elements. You now see only the elements of area 1. ANSYS still "knows" about all the lines and nodes (try plotting them), but area 1 and its elements are the only elements and area selected. Select Everything and Replot when you're ready to work with the rest of the model.
This may seem confusing or very involved. Once you get the hang of it though, it's not so bad. If you're working with complex geometries, picking elements can be tricky, even using Box or Polygon. Although Selecting in this manner adds a number of addional steps, they are simple and exact steps.
There are many uses for Selecting. Some are shown in some of the tutorial examples. Others will come to you as the situation demands. You be comfortable with playing around with these types of things. Remeber that you can always check what's selected by Replotting and the like.
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