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An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
Published on: December 4, 2017
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Correlation in thermal fluctuations induced by phase-locked hydrodynamic modes
Xiaohui Deng1, Xiaoping Wang2, Ping Sheng1
1Department of Physics, HKUST, Clear Water Bay, Kowloon, Hong Kong, China.
Physical Review. E
|June 17, 2021
Summary
Modulating fluid channel boundaries selectively suppresses thermal fluctuations, creating mesoscopic spatial correlations. This manipulation of hydrodynamic modes (HMs) alters diffusion constants, impacting fluid behavior at small scales.
Area of Science:
- Fluid dynamics
- Statistical mechanics
- Mesoscopic physics
Background:
- Thermal fluctuations are fundamental equilibrium phenomena in fluids, governed by molecular collisions.
- Hydrodynamic modes (HMs) represent thermal fluctuations as collections of vortex-antivortex pairs with random phases.
- The Navier slip boundary condition is commonly used to describe fluid behavior near surfaces.
Purpose of the Study:
- To investigate the effect of periodic modulation of the Navier slip boundary condition on thermal fluctuations in a 2D fluid channel.
- To demonstrate the selective suppression of noncommensurate hydrodynamic modes and phase locking of eigenmodes.
- To explore the resulting mesoscopic-scale spatial correlations in thermal fluctuations.
Main Methods:
- Utilizing a continuum fluid model with Navier slip boundary conditions.
- Representing hydrodynamic modes as periodic arrays of vortex and antivortex pairs.
- Applying periodic modulation to the slip boundary condition.
- Evaluating the fluctuation-dissipation theorem to determine spatial correlations and diffusion constants.
- Comparing results with molecular dynamics simulations.
Main Results:
- Periodic modulation of the slip boundary condition selectively suppresses noncommensurate hydrodynamic modes.
- The remaining hydrodynamic modes become phase-locked, leading to mesoscopic-scale spatial correlations.
- A spatially varying diffusion constant is observed, consistent with the fluctuation-dissipation theorem.
- Molecular dynamics simulations show good agreement with the theoretical predictions.
Conclusions:
- Hydrodynamic modes in mesoscopic systems can be physically manipulated, not just serve as a mathematical construct.
- Modulated slip boundary conditions offer a method to control thermal fluctuations and their spatial correlations.
- This control over hydrodynamic modes has implications for understanding and engineering fluid behavior at the mesoscopic scale.
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