Session: 16-01-01: Government Agency Student Poster Competition

Paper Number: 150447

150447 - Understanding Bubble Formation on Porous Superhydrophobic Surfaces 

Superhydrophobic surfaces (SHS), known for their high resistance to wetting, offer significant potential in marine applications, such as reducing friction drag in turbulent flows and preventing biofouling and corrosion. These applications can lead to reduced fossil fuel emissions. However, maintaining the plastron (gas layer) on SHS under varying conditions, such as pressure, gas dissolution, and flow-induced shear, remains a major challenge. This research aims to investigate bubble formation on porous SHS through controlled gas injection, contributing to the advancement of SHS applications in marine environments.

We will employ a series of experimental techniques including SHS coating application, controlled gas injection, and flow rate measurement within an acrylic water chamber to analyze the stability and longevity of the gas layer. Our objectives include measuring the effect of gas injection on bubble formation across porous surfaces by adjusting at various psi, assessing the impact of varying porosities using two different porosity discs, comparing bubble formation on SHS-coated versus non-coated surfaces, and developing a predictive model for bubble size, quantity, and gas flow rate under varying experimental conditions.

The main experimental setup involves a high-pressure acrylic water chamber and aluminum plugs with glued porous discs, with pressure adjusted at various psi. Bubble capture will be facilitated by a Chronos high-speed camera at a resolution of 1280x1024 and 1,069 fps. Initial experiments will focus on non-coated porous surfaces to establish baseline bubble formation patterns, followed by comparisons with SHS-coated surfaces. The gas flow rate will be accurately determined using a pressurized tank with valves for air intake and water expulsion.

The experimental results revealed significant differences in bubble formation and gas flow rates between non-coated and SHS-coated porous surfaces. For non-coated surfaces, small bubbles formed at lower pressures, with bubble coalescence occurring at 8 psi for 2 µm surfaces and 3 psi for 20 µm surfaces. In contrast, SHS-coated surfaces displayed no tiny bubbles, with a stable gas layer forming uniformly and bubble coalescence occurring at lower pressures of 5 psi for 2 µm surfaces and 1.5 psi for 20 µm surfaces. Gas flow rates increased with pressure for both non-coated and SHS-coated surfaces. However, the presence of water generally reduced gas flow rates, except for SHS-coated surfaces, which maintained efficient gas flow under submerged conditions. These results indicate that SHS coatings enhance the stability and uniformity of the gas layer, reduce the pressure required for bubble formation, and optimize gas flow rates, making them highly suitable for marine applications where reducing friction drag and preventing biofouling and corrosion are critical.

Presenting Author: Dillon Singh University of Massachusetts Dartmouth

Presenting Author Biography: I am Dillon Singh, a recent honors graduate in Engineering Science from Hudson County Community College. This fall, I will be embarking on an exciting new journey at Rutgers School of Engineering, where I will be majoring in Material Science Engineering. Over the summer, I had the incredible opportunity to participate in the REU program at UMass Dartmouth, focusing on Advanced Interdisciplinary Materials Research for Maritime Applications.

Authors:

Dillon Singh University of Massachusetts Dartmouth
Shabnam Mohammadshahi University of Massachusetts Dartmouth
Hangjian Ling University of Massachusetts Dartmouth