Confined elastic curves
This work addresses the challenge of enforcing topological constraints in shape optimization for confined elastic curves, which is relevant to problems in materials science and geometry.
The authors minimize Euler's elastica energy for simple closed curves confined to the unit disk using a phase-field method with a diffuse approximation of the winding number to enforce topological constraints. Numerical results using subdivision surface finite elements are presented.
We consider the problem of minimizing Euler's elastica energy for simple closed curves confined to the unit disk. We approximate a simple closed curve by the zero level set of a function with values +1 on the inside and -1 on the outside of the curve. The outer container now becomes just the domain of the phase field. Diffuse approximations of the elastica energy and the curve length are well known. Implementing the topological constraint thus becomes the main difficulty here. We propose a solution based on a diffuse approximation of the winding number, present a proof that one can approximate a given sharp interface using a sequence of phase fields, and show some numerical results using finite elements based on subdivision surfaces.