Thermo-orientation in fluids of arbitrarily shaped particles

Area of Science:

• Statistical Mechanics
• Computational Physics
• Fluid Dynamics

Background:

• Nonequilibrium Molecular Dynamics (NEMD) simulations have shown that fluids composed of uncharged dumbbell-like particles exhibit preferential orientation when subjected to a temperature gradient.
• This phenomenon, termed thermo-orientation, scales linearly with the temperature gradient and is influenced by differences in particle bead shape or mass.

Purpose of the Study:

• To investigate the underlying mechanisms and microscopic determinants of thermo-orientation in fluids.
• To extend NEMD simulations to various particle shapes and mass distributions, including chiral particles, to understand thermo-orientation.
• To develop a microscopic model for predicting thermo-orientation based on particle characteristics.

Main Methods:

• Performed extensive nonequilibrium Molecular Dynamics (NEMD) simulations.
• Simulated uncharged particles with diverse shapes and mass distributions, including chiral configurations.
• Analyzed simulation data to identify correlations between particle properties and thermo-orientation.

Main Results:

• Confirmed that thermo-orientation magnitude depends on particle shape and mass distribution.
• Demonstrated that the phenomenon is observable in various particle geometries beyond simple dumbbells.
• Developed a microscopic model that successfully rationalizes the numerical results.

Conclusions:

• The study provides a microscopic model, grounded in local equilibrium, to explain thermo-orientation.
• This model allows for the prediction of thermo-orientation response for arbitrarily shaped particles based on their shape and mass distribution.
• The findings offer fundamental insights into the behavior of fluids under thermal gradients.