  This paper deals with the modelling of superconducting and resistive wires
with a helicoidal symmetry, subjected to an external field and a transport
current. Helicoidal structures are three-dimensional, and therefore yield
computationally intensive simulations in a Cartesian coordinate system. We show
in this paper that by working instead with a helicoidal system of coordinates,
the problem to solve can be made two-dimensional, drastically reducing the
computational cost. We first introduce the state-of-the-art approach and apply
it on the h-phi-formulation with helicoidally symmetric boundary conditions
(e.g., axial external magnetic field, with or without transport current), with
an emphasis on the function space discretization. Then, we extend the approach
to general boundary conditions (e.g., transverse external magnetic field) and
present numerical results with linear materials. In particular, we discuss the
frequency-dependent losses in composite wires made of superconducting filaments
embedded in a resistive matrix. Finally, we provide outlook to the application
of the generalized model with nonlinear materials.
