Three-dimensional singular boundary elements for corner and edge singularities in potential problems

It is well known that the spatial derivative of the potential field governed by the Laplace and Poisson equations can become infinite at corners (in two and three dimensions) and edges (in three dimensions). Conventional elements in the finite element and boundary element methods do not give accurate results at these singular locations. This paper describes the formulation and implementation of new singular elements for three-dimensional boundary element analysis of corner and edge singularities in potential problems. Unlike the standard element, the singular element shape functions incorporate the correct singular behavior at the edges and corners, specifically the eigenvalues, in the formulation. The singular elements are used to solve some numerical examples in electrostatics, and it is shown that they can improve the accuracy of the results for capacitance and electrostatic forces quite significantly. The effects of the size of the singular elements are also investigated.