Tonks-Frenkel instability in electrolyte under high-frequency AC electric fields

Area of Science:

• Physics
• Electrochemistry
• Fluid Dynamics

Background:

• Electrolyte surface behavior under electric fields is crucial for various applications.
• High-frequency AC fields offer unique control over electrochemical systems, avoiding unwanted reactions.
• Previous studies on electric field-induced instabilities often focused on DC fields.

Purpose of the Study:

• To theoretically investigate the instability of electrolyte surfaces subjected to high-frequency AC electric fields.
• To analyze the formation of coherent structures and Taylor cones under these conditions.
• To compare theoretical predictions with experimental and prior theoretical results.

Main Methods:

• Utilizing the theory of unsteady electric double layers.
• Analytical solution of linear stability for a 1D quiescent stationary state.
• Direct Numerical Simulation (DNS) of the full nonlinear system of equations.
• Evaluating Taylor cone angles under varying conditions.

Main Results:

• High-frequency AC fields induce instabilities similar to DC fields due to the system's response to the slower component of the Coulomb force.
• Linear stability analysis and DNS show good agreement, with a narrow band of instability near the maximum growth rate.
• Nonlinear evolution leads to coherent structures resembling Taylor cones with angles between 30° and 60°.

Conclusions:

• The study provides a theoretical framework for understanding high-frequency AC electric field-induced electrolyte surface instabilities.
• The formation of Taylor cones at high frequencies is confirmed, with angles differing from DC field cases.
• The findings align with experimental observations and contribute to the theoretical understanding of AC electrokinetics.