Flexible conformable hydrophobized surfaces for turbulent flow drag reduction.

Area of Science:

• Fluid Dynamics
• Materials Science
• Surface Science

Background:

• Superhydrophobic surfaces utilize a trapped gas layer (plastron) in the Cassie-Baxter state to reduce drag.
• This gas layer facilitates slip, leading to significant drag reduction in various applications.

Purpose of the Study:

• To develop and evaluate flexible, large-area superhydrophobic surfaces for drag reduction.
• To compare drag reduction efficiencies of two distinct fabrication methods.

Main Methods:

• Fabrication of superhydrophobic surfaces with large roughness (electrodeposition on copper mesh) and small roughness (carbon nanoparticles in PDMS).
• Characterization using Scanning Electron Microscopy (SEM) and confocal microscopy under submerged conditions.
• Drag reduction measurements for turbulent flows (Reynolds numbers 10,000–32,500).

Main Results:

• Electrodeposited copper mesh cylinders demonstrated up to 32% drag reduction compared to a wetted state.
• Soot-embedded PDMS cylinders achieved 30% drag reduction compared to a plain cylinder.
• Both methods produced functional superhydrophobic surfaces capable of maintaining a plastron.

Conclusions:

• Flexible superhydrophobic surfaces can be fabricated using electrodeposition and nanoparticle embedding for significant drag reduction.
• These surfaces show promise for applications requiring reduced frictional resistance in aquatic environments.
• The study validates the effectiveness of superhydrophobic surfaces in turbulent flow regimes.