Heat conduction in a three-dimensional momentum-conserving fluid.

Area of Science:

• Nanoscale science
• Condensed matter physics
• Fluid dynamics

Background:

• Understanding nanoscale energy transport and reduced dimensionality effects on transport coefficients is crucial for nonequilibrium properties.
• Thermal conductivity and its dependence on system size and dimensionality are key areas of research in materials science.

Purpose of the Study:

• To investigate heat conduction in a three-dimensional (3D) fluid using multiparticle collision dynamics.
• To explore the size dependence of energy transport and the transition from 3D to one-dimensional (1D) behavior.
• To verify Fourier's law and existing theories for 3D fluids under nonequilibrium conditions.

Main Methods:

• Non-equilibrium and equilibrium simulations of heat conduction.
• Utilized multiparticle collision dynamics (MPCD) for fluid simulation.
• Interaction of the fluid with two thermal walls to drive heat flux.

Main Results:

• The bulk 3D fluid demonstrates finite, nondiverging thermal conductivity, consistent with normal transport.
• A crossover to 1D abnormal thermal conductivity behavior is observed for large aspect ratios.
• A transition from normal to abnormal transport was demonstrated via energy current decomposition.

Conclusions:

• The findings provide direct verification of Fourier's law for the simulated 3D fluid.
• Results confirm the validity of existing theories for 3D fluid transport.
• Abnormal heat transport phenomena persist in quasi-1D fluids across various sizes.