Superhydrophobic substrates allow the generation of giant quasi-static bubbles

Rubio-Rubio, Mariano; Bolaños-Jiménez, R.; Martı́nez-Bazán, C.; Muñoz-Hervás, J.C.; Sevilla, A.

doi:10.1017/jfm.2020.1098

Cited by 10 publications

(4 citation statements)

References 41 publications

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“…When the contact angle approaches 145°, the uncertainty to estimate D B increases and the model is not able to predict the bubble geometry for angles beyond this value (IV in Figure 6). The reason is that surfaces with θ > 150°, the so‐called “superhydrophobicity,” show very low wettability of the liquid phase and the gas phase tends to spread over the solid surface forming a thin film at the initial stages of bubble formation 41 . These superhydrophobic surfaces are not of practical interest for bubble generation as they result in bubble coalescence in multiple hole systems, drastically increasing D B .…”

Section: Resultsmentioning

confidence: 99%

Bubble generation in refractory porous plugs: The role of the ceramic surface composition

Falsetti

Muche

Andreeta

et al. 2022

Int J Ceramic Engine & Sci

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Porous ceramic plugs are refractory devices applied in the steel ladle to inject gas bubbles into the liquid metal, aiming at its chemical and thermal homogenization, and the removal of non-metallic inclusions. Regarding its wear and corrosion resistance, the plug composition typically exhibits a low wettability by liquid steel to limit its infiltration into the porous structure. However, an additional aspect for the performance of plugs is their ability to control the size of the generated bubble, maximizing the likelihood of capturing inclusions. Based on the importance of this process to attain high-performance materials, this work studied the injection of gas into liquid media through ceramic capillary structures, focusing on the influence of the pore diameter and the contact angle upon the size of the generated bubble. The available models in the literature were analyzed and compared to the experimental results for a water-air system. As an outcome, a shape-corrected model for bubbling is proposed highlighting the region where the material dominates over the pore diameter to dictate the bubble size.Extending the model to the steel ladle, the results suggest the composition of the ceramic plug's surface as a key aspect to improve the cleanliness of the molten steel.

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Section: Resultsmentioning

confidence: 99%

Bubble generation in refractory porous plugs: The role of the ceramic surface composition

Falsetti

Muche

Andreeta

et al. 2022

Int J Ceramic Engine & Sci

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“…In order to overcome this issue, a glycerol-water (GW) mixture was employed together with a superhydrophobic substrate (Rustoleum ® NeverWet™) coating the air injector. The necessary diameter of the superhydrophobic substrate was obtained using the correlation given by Rubio-Rubio et al 54 . The GW mixture composition was 74.16-74.89% in weight of glycerol, depending on the case.…”

Section: Experimental Setup and Methodsmentioning

confidence: 99%

“…Moreover, the physical properties of GW mixtures are not as stable as silicon oils, and therefore the values of the control parameters slightly varied from experiment to experiment. In addition, the established rising paths depended on the initial injection conditions, which were not exactly the same in all the experiments, since the bubbles were generated using a superhydrophobic substrate (see Rubio-Rubio et al 54 for more details) instead of a conventional injector as in Cases 1 and 2. Furthermore, bubble shape oscillations were observed along the rise of these bubbles.…”

Section: B Planar Zigzag Regimementioning

confidence: 99%

Bubble rising near a vertical wall: Experimental characterization of paths and velocity

Estepa-Cantero,

Martínez-Bazán,

Bolaños-Jiménez

2024

Preprint

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The trajectories of a single bubble rising in the vicinity of a vertical solid wall are experimentally investigated. Distinct initial wall-bubble distances are considered for three different bubble rising regimes, i.e. rectilinear, planar zigzag, and spiral. The problem is defined by three control parameters, namely the Galilei number, Ga, the Bond number, Bo, and the initial dimensionless distance between the bubble centroid and the wall, L. We focus on high-Bond numbers, varying L from 1 to 4, and compare the results with the corresponding unbounded case L → ∞ . In all cases, the bubble deviates from the expected unbounded trajectory and migrates away from the wall as it rises due to the overpressure generated in the gap between the bubble and the wall. This repulsion is more evident as the initial wall-bubble distance decreases. Moreover, in the planar zigzagging regime, the wall is found to impose a preferential zigzagging plane perpendicular to it when L is small enough. Only slight wall effects are observed in the velocity or the oscillation amplitude and frequency. The wall migration effect is more evident for the planar zigzagging case and less relevant for the rectilinear one. Finally, the influence of the vertical position of the wall is also investigated. When the wall is not present upon release, the bubbles have the expected behavior for the unbounded case and experience the migration only instants before reaching the wall edge. This repulsion is, in general, more substantial than in the initially-present-wall case.

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“…This expansion, however, is not indefinite. Once the contact line reaches its maximum diameter, further air injection results in the vertical ascent of the bubble, culminating in its detachment from the surface under the influence of buoyancy 31 (Figure 3e and Movie S3). The mechanism of air spreading in a pyramid-shaped superhydrophobic surface can be explained as follows: when the surface has wedge-shaped grooves, an air−liquid interface forms between adjacent walls during air.…”

Section: Gas−liquid Interface Stabilitymentioning

confidence: 99%

Pyramid-Shaped Superhydrophobic Surfaces for Underwater Drag Reduction

Zhang,

Wan,

Zhou

et al. 2024

ACS Appl. Mater. Interfaces

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Superhydrophobic surfaces hold immense potential in underwater drag reduction. However, as the Reynolds number increases, the drag reduction rate decreases, and it may even lead to a drag increase. The reason lies in the collapse of the air mattress. To address this issue, this paper develops a pyramid-shaped robust superhydrophobic surface with wedged microgrooves, which exhibits a high gas fraction when immersed underwater and good ability to achieve complete spreading and recovery of the air mattress through air replenishment in the case of collapse of the air mattress. Pressure drop tests in a water tunnel confirm that with continuous air injection, the drag reduction reaches 64.8% in laminar flow conditions, substantially greater than 38.4% in the case without air injection, and can achieve 50.8% drag reduction in turbulent flow. This result highlights the potential applications of superhydrophobic surfaces with air mattress recovery for drag reduction.

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Superhydrophobic substrates allow the generation of giant quasi-static bubbles

Abstract: Abstract

Cited by 10 publications

References 41 publications

Bubble generation in refractory porous plugs: The role of the ceramic surface composition

Bubble generation in refractory porous plugs: The role of the ceramic surface composition

Bubble rising near a vertical wall: Experimental characterization of paths and velocity

Pyramid-Shaped Superhydrophobic Surfaces for Underwater Drag Reduction

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