Influence of Flow on Longevity of Superhydrophobic Coatings

Abstract

Previous studies have demonstrated the capability of superhydrophobic surfaces to produce slip flow and drag reduction, which properties hold considerable promise for a broad range of applications. However, in order to implement such surfaces for practical utilizations, environmental factors such as water movement over the surface must be observed and understood. In this work, experiments were carried out to present a proof-of-concept study on the impact of flow on longevity of polystyrene fibrous coatings. The time-dependent hydrophobicity of a submerged coating in a pressure vessel was determined while exposing the coating to a rudimentary wall-jet flow. Rheological studies were also performed to determine the effect of the flow on drag reduction. The results show that the longevity of the surface deteriorates by increasing the flow rate. The flow appears to enhance the dissolution of air into water, which leads to a loss of drag reduction.

Polymeric Slippery Coatings: Nature and Applications

“…Solid and broken lines are best fit of experimental data in forced, free and mixed convection regimes. From Samaha et al [108].…”

“…They studied the effect of hydrostatic pressure [76], water flow [108], and salinity of water [109]. Figure 38 shows an example of the longevity measurements versus pressure conducted for the fibrous coatings.…”

“…Another environmental condition, water movement, was also studied [108]. Experiments were carried out to investigate the impact of flow on longevity of polystyrene fibrous coatings.…”

Superhydrophobic surfaces for corrosion protection: a review of recent progresses and future directions

“…Obviously, the effectiveness of superhydrophobic surfaces to protect immersed structures largely depends on the underwater stability of the air films which rapidly decays with increasing hydraulic pressure, [115][116][117] flow, 118 or salinity 119 of the surrounding fluids. In fact, almost none of the surfaces developed so far have shown an acceptably long underwater superhydrophobicity for practical applications.…”

Development of a Miniature Shear Sensor for Direct Comparison of Skin-Friction Drags

“…The importance has been recognized only very recently, as the plastron loss became the main roadblock against testing SHPo surfaces in turbulent flows especially in large facilities. Samaha et al (2012a) have measured that the longevity of the plastron was shortened as the flow rate over the SHPo surface increased, and Emami et al (2013) have numerically investigated the unsteady behavior of the plastron interface by considering the diffusion of trapped air over time. They showed that the maximum hydrostatic pressure sustainable above the plastron decreases with increasing width of the water-air interface.…”