Influence of nonlinear coordinate transformation on thermal cloaking performances of multilayered cylindrical thermal cloaks

Layered discretization is an efficient way of realizing thermal cloaks. The aim of this paper is to investigate the effect of nonlinear coordinate transformation on the thermal cloaking performance of multilayered cylindrical thermal cloak. Two indexes are defined to quantify the thermal cloaking performance. Nonlinear coordinate transformations with different forms are established to design the multilayered structures and the thermal cloaking performances are analyzed by full-wave simulations. The results show that the thermal cloaking performances of multilayered structures are directly influenced by the form of coordinate transformation which determines the distributions of heat flows in the cloak region. Through the active changing of the form of coordinate transformation, the thermal cloaking performance of multilayered structure can be controlled and optimized. In addition, a three-piecewise linear coordinate transformation is designed to concentrate the heat flux into the middle region of the cloak and the corresponding multilayered structure is demonstrated to have near-perfect thermal cloaking performance. These results may provide a beneficial guidance to achieve performance improvements for multilayered structures of thermal cloaks.