Controlling thermal waves of conduction and convection

Abstract

Electromagnetic wave refractions have been widely explored due to their profound physics and practical applications, especially the negative refraction. However, the hyperbolic feature of the Maxwell equations makes it difficult to extend the related physics to the Fourier conduction because the Fourier equation is parabolic. To solve the problem, we study thermal waves of conduction and convection because convection can additionally introduce the hyperbolic feature to heat transfer. We further design convection-assisted metamaterials to realize the positive, vertical, and negative refractions of thermal waves, which have a phenomenal analog of electromagnetic wave refractions despite different mechanisms. The negative refraction of thermal waves means that the incident and refractive thermal waves are at the same side of the normal, but the wave vector and energy flow are still along the same direction. As a model application, we apply the refractive behaviors to design a thermal wave concentrator which can increase wave numbers and energy flows. This work provides insights into thermal wave manipulation, which may have potential applications in thermal wave imaging.