On filter boundary conditions in topology optimization

Most research papers on topology optimization involve filters for regularization. Typically, boundary effects from the filters are ignored. Despite significant drawbacks the inappropriate homogeneous Neumann boundary conditions are used, probably because they are trivial to implement. In this paper we define three requirements that boundary conditions must fulfill in order to eliminate boundary effects. Previously suggested approaches are briefly reviewed in the light of these requirements. A new approach referred to as the "domain extension approach" is suggested. It effectively eliminates boundary effects and results in well performing designs. The approach is intuitive, simple and easy to implement.