Choosing boundary conditions

18 Aug Choosing boundary conditions

Sometimes CFD and FEM simulations can really be hard to complete. If you are un-experienced, you may find some of the basic tricks of this type of analysis quite difficult to understand. In these situation please don’t panic: there are very simple operation to accomplish to obtain an impressive result. One of these operation is understanding the meaning of boundary conditions. As usually in these situation a practical example can really help you understanding what is happening.

Let’s just consider a simple pump simulation. As you may expect, while the impeller rotates the flows is pushed from the central axis to the external part of the impeller. If we look carefully the impeller, as in this image, we can see an axial symmetry of the geometry. Obviously, to simplify the simulation and reduce the computational costs, it is fundamental to take advantage of this symmetry and reduce the overall simulation domain to a slice of the impeller. When we complete the 3D model of the impeller slice (remember to follow our guidelines for this) an important phase starts: the definition of surface groups. These groups, sketched here, are fundamentals: they can be used to define mesh refinements, to impose boundaries and, during post-processing, to make fundamental calculations. This phase is generally made during the geometry step, when the user has the possibility to group faces into a single boundary as per the following video.