Characterization of the Liquid–Lubricant Interface in a Dovetail Cavity for a Viscous Laminar Flow

Ahuja, Ratan Bharat; Gaddam, Anvesh; Joshi, Suhas S.; Agrawal, Amit

doi:10.1021/acs.iecr.2c02874

Cited by 4 publications

(1 citation statement)

References 34 publications

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“…Conducting finite volume simulations, Ahuja et al 201 characterized the liquid/lubricant interface in a dovetail cavity, considering viscosity contrasts of 0.2−1 between the outer fluid and the lubricant, in the laminar range of 100 ≤ R ≤ 1000. The meniscus shape was characterized for the studied range of the viscosity contrast and Reynolds number.…”

Section: Numerical Simulationsmentioning

confidence: 99%

Modeling of Shear Flows over Superhydrophobic Surfaces: From Newtonian to Non-Newtonian Fluids

Rahmani,

Larachi,

Taghavi

2024

ACS Eng. Au

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The design and use of superhydrophobic surfaces have gained special attentions due to their superior performances and advantages in many flow systems, e.g., in achieving specific goals including drag reduction and flow/droplet handling and manipulation. In this work, we conduct a brief review of shear flows over superhydrophobic surfaces, covering the classic and recent studies/ trends for both Newtonian and non-Newtonian fluids. The aim is to mainly review the relevant mathematical and numerical modeling approaches developed during the past 20 years. Considering the wide ranges of applications of superhydrophobic surfaces in Newtonian fluid flows, we attempt to show how the developed studies for the Newtonian shear flows over superhydrophobic surfaces have been evolved, through highlighting the major breakthroughs. Despite the fact that, in many practical applications, flows over superhydrophobic surfaces may show complex non-Newtonian rheology, interactions between the non-Newtonian rheology and superhydrophobicity have not yet been well understood. Therefore, in this Review, we also highlight emerging recent studies addressing the shear flows of shear-thinning and yield stress fluids in superhydrophobic channels. We focus on reviewing the models developed to handle the intricate interaction between the formed liquid/air interface on superhydrophobic surfaces and the overlying flow. Such an intricate interaction will be more complex when the overlying flow shows nonlinear non-Newtonian rheology. We conclude that, although our understanding on the Newtonian shear flows over superhydrophobic surfaces has been well expanded via analyzing various aspects of such flows, the non-Newtonian counterpart is in its early stages. This could be associated with either the early applications mainly concerning Newtonian fluids or new complexities added to an already complex problem by the nonlinear non-Newtonian rheology. Finally, we discuss the possible directions for development of models that can address complex non-Newtonian shear flows over superhydrophobic surfaces.

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Section: Numerical Simulationsmentioning

confidence: 99%

Modeling of Shear Flows over Superhydrophobic Surfaces: From Newtonian to Non-Newtonian Fluids

Rahmani,

Larachi,

Taghavi

2024

ACS Eng. Au

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Hydrodynamic drag reduction in ribbed microchannel with infused non-Newtonian lubricants

R. Nair,

Chandran,

Ranjith

2024

Physics of Fluids

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Liquid-infused surfaces have recently gained prominence in engineering applications owing to their versatile characteristics such as self-cleaning, anti-fogging, drag reduction, and enhanced heat transfer. In this article, a numerical analysis of pressure-driven flow past a periodic array of rectangular transverse grooves infused with non-Newtonian immiscible lubricants is performed. The volume of fluid method is employed to capture the interface between primary and secondary fluids, and the power-law model is deployed to mimic the non-Newtonian lubricant. The drag reduction capability of the microchannel is examined for various parameters such as Reynolds number, liquid fraction, viscosity ratio, viscosity index, and contact angle. It is observed that the introduction of a non-Newtonian fluid (shear-thickening or shear-thinning) drastically modifies the interface velocity and hydrodynamic resistance. In particular, a shear-thinning lubricant enhances the slip length as the viscosity index (n) is reduced owing to the reduced viscosity at the interface. Note that, for a lubricant having n = 0.7, the percentage improvement in the slip length is 382% in comparison with a Newtonian counterpart having the same viscosity ratio, N = 0.1. Importantly, the introduction of a shear-thinning lubricant with a viscosity ratio N = 5, a liquid fraction of 0.8, and a behavior index n = 0.7 yielded a pressure drag reduction of 63.6% with respect to a classical no-slip channel and of 23% with reference to a microchannel with the Newtonian lubricant. Moreover, at high Reynolds numbers, Re→50, the drag mitigation is slightly lowered due to the primary vortex shift in the cavity. Furthermore, the effect of the interface contact angle (θc) is investigated, as θc drops from 90° (flat) to 45° (convex); the meniscus curvature is enhanced, and the effective slip length is reduced. These observations suggest that a shear-thinning lubricant-infused microchannel is a promising candidate for drag reduction in lab-on-chip applications.

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Lubricant depletion and interface dynamics in liquid-infused microchannel subjected to external oscillations

Ahuja,

Joshi,

Agrawal

2024

Physics of Fluids

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Lubricant-infused surfaces (LIS) find suitability in a plethora of applications due to their omniphobic functionalities. LIS, however, lose their functionality in the absence of the lubricant. A majority of the studies have focused on understanding the liquid-repellent properties of LIS, but only limited attention has been paid to understanding their durability. In this work, we focus on the interface dynamics for prolonging the durability of LIS during transport for food packaging applications. We analyze the lubricant retention characteristics within cavities when subjected to pure oscillations (zero net flow). The microchannel is excited at f=0.1–10 Hz for viscosity ratio (μr=0.4–1.0 and μr=1.8) for a dovetail cavity with lubricant of two different densities. The failure and stability of LIS are characterized based on the orientation of velocity vectors and the position of vortex formed within the cavity. A random orientation of velocity vectors within the cavity signifies failure of LIS. External oscillations cause the interface to rupture and form drops. Upon rupture, drops of both the external liquid and lubricant are present in the cavity leading to a chaotic interaction between the two fluids and finally resulting in random orientation of vectors. On the other hand, a vortex formed at the liquid–lubricant interface signifies a stable LIS with an intact meniscus. The results show that the stability of LIS has a strong dependence on the viscosity of external liquid and the density of lubricant. A more viscous external liquid and a denser lubricant dampen the vibration effects, thereby exhibiting a stable state with an intact meniscus. The amplitude variation (A=0.001–0.1 m) surprisingly does not show a significant variation in the failure states. Furthermore, the rate of depletion of lubricant from the cavity and its effect on meniscus failure with time are also illustrated. The results from this work will aid in realizing a robust LIS system with prolonged lubricant retention.

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Characterization of the Liquid–Lubricant Interface in a Dovetail Cavity for a Viscous Laminar Flow

Cited by 4 publications

References 34 publications

Modeling of Shear Flows over Superhydrophobic Surfaces: From Newtonian to Non-Newtonian Fluids

Modeling of Shear Flows over Superhydrophobic Surfaces: From Newtonian to Non-Newtonian Fluids

Hydrodynamic drag reduction in ribbed microchannel with infused non-Newtonian lubricants

Lubricant depletion and interface dynamics in liquid-infused microchannel subjected to external oscillations

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