Study on the Performance of a Surface with Coupled Wettability Difference and Convex-Stripe Array for Improved Air...

Area of Science:

• Fluid Dynamics
• Surface Science
• Materials Engineering

Background:

• Friction drag on superhydrophobic surfaces is reduced by an entrapped air layer.
• Maintaining air layer stability is crucial for energy savings and pollution reduction.
• Kelvin-Helmholtz instability, driven by density and velocity differences, destabilizes the air layer.

Purpose of the Study:

• To develop and experimentally evaluate a novel superhydrophobic surface for enhanced air layer stability.
• To investigate the mechanisms of air layer destabilization in a swirling flow field.
• To quantify the drag reduction performance of the developed surface.

Main Methods:

• Fabrication of a superhydrophobic surface using laser engraving and fluorine modification.
• Incorporation of a convex-stripe array and wettability difference treatment.
• Experimental study in a von Kármán swirling flow field to analyze air layer stability and critical Reynolds number (Re_c).

Main Results:

• The critical Reynolds number (Re_c) for a uniform superhydrophobic surface was 1.62 × 10^5.
• A surface with a convex stripe (SCSS_P) increased Re_c to 3.24 × 10^5.
• Coupling wettability difference treatment with the convex-stripe array design increased Re_c to 4.05 × 10^5, maintaining ~30% drag reduction.

Conclusions:

• The combined strategy of wettability difference and convex-stripe array significantly enhances air layer stability.
• This improved stability leads to a higher critical Reynolds number and sustained drag reduction.
• The developed surface offers a promising approach for reducing energy consumption and environmental impact from friction drag.