Litz wire is a type of cable, which consists from many individual insulated conductor strands. These are twisted together to minimize the skin effect and proximity effect losses. Strand position relative to other strands is varying along the Litz wire length, cross-sections of such cable are turning, and it may look like this this setup requires 3D analysis. But 2D simulation provides adequate accuracy and is much more practical. QuickField software may be effectively applied for the Litz simulation using two different approaches, showcased in the Litz wire losses and and Stranded wire simulations examples.
Wikipedia :: Litz_wire