In certain ultrapure, high-conductivity materials, heat can deviate from Fourier’s law and behave like a fluid, forming vortices, temperature waves, and backflow — a regime known as phonon hydrodynamics. A COMSOL blog post explains how researchers at Columbia University used the Physics Builder in COMSOL Multiphysics to develop a custom interface, the Viscous Heat Equations, to study this behavior in realistic geometries.
The interface couples temperature with phonon drift velocity, similar to Navier–Stokes equations, to capture nondiffusive heat transport. Steady-state simulations revealed vortex formation and thermal backflow, while time-dependent simulations captured heat vortices forming, moving, and reversing over time. This work offers a practical bridge between microscopic transport theory and continuum-scale device modeling.
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