S-shaped velocity deformation induced by ionic hydration in aqueous salt solution flow

Area of Science:

• Physical Chemistry
• Nanofluidics
• Computational Fluid Dynamics

Background:

• Ionic hydration shells are key microscopic features in aqueous salt solutions.
• Their contribution to solution flow behavior, particularly in nanochannels, is of significant interest.

Purpose of the Study:

• To investigate the influence of ionic hydration shells on fluid flow behavior within nanochannels.
• To establish a theoretical and simulation-based understanding of the relationship between ionic properties and nanochannel flow profiles.

Main Methods:

• Molecular dynamic simulations were employed to model nanochannel flow.
• Theoretical analysis was conducted to correlate energy density within hydration shells to velocity profile deformation.
• Simulations were performed for various chloride salt solutions with different cations (K, Na, Ca, Mg, Al) and varying valence numbers.

Main Results:

• An S-shaped velocity profile was observed in nanochannel flow, induced by ionic hydration shells.
• A linear relationship was identified between the energy density of the first hydration shell and the deformation strength of the velocity profile (quantified by curvature length).
• This relationship was validated across various salt solutions and flow conditions, including varying flow velocity and channel width.

Conclusions:

• Ionic hydration shells significantly impact nanochannel flow dynamics, leading to characteristic S-shaped velocity profiles.
• The curvature length serves as a reliable metric for evaluating nano flow behavior.
• The findings offer valuable insights for the design and optimization of nanofluidic devices.