Droplet Mobility on Slippery Lubricant Impregnated and Superhydrophobic Surfaces under the Effect of Air Shear Flow

Abstract

The focus of this study is to investigate and compare the behavior of a droplet on superhydrophobic (SHS) and slippery lubricant impregnated (SLIPS) surfaces under the effect of air shear flow. In this regard, both experimental and numerical analyses have been conducted to compare their performance on droplet mobility under different air speeds. Two different lubricants have been utilized to scrutinize their effect on droplet movement. The numerical simulations have been performed based on the volume of fluid method coupled with the large eddy simulation turbulent model in conjunction with the dynamic contact angle method in addition to a model that can represent the effect of lubricants on slippery surfaces. The numerical simulations are compared with the experimental study in order to shed light on the underlying mechanisms. The results showed that under the same conditions, the critical velocity for droplet movement on the superhydrophobic surfaces is lower than that on the slippery lubricant impregnated surfaces due to the smaller droplet base diameter and the larger contact angle. The hydrodynamics of droplet mobility on superhydrophobic surfaces exhibits a rolling behavior while for the slippery lubricant impregnated surfaces a combination of rolling and sliding is observed. Beyond the critical airflow speed, a complete droplet shedding on all surfaces occurs. The wetting length and position of the droplet on superhydrophobic and slippery surfaces have been measured. On slippery surfaces, the speed of droplets is greatly affected by the lubricant properties while similar behavior in the wetting lengths is observed.

Numerical Investigations of the Kinetic Behavior of Adhering Droplets on the Inclined Windshield in Airflows

“…The encrypted region and boundary layer division of the whole computational domain are shown in Figure 5. The dynamic contact angle model used in association with a flow model has been found to be an accurate method to represent the contact angle variation in fluid flow [40]. Thus, the dynamic contact angle is introduced to reproduce the transient contact angle values between the droplet and the wall more accurately.…”

Liquid–Solid Impact Mechanism, Liquid Impingement Erosion, and Erosion-Resistant Surface Engineering: A Review

“…A comprehensive review of recent advances in superhydrophobic surfaces can be found in [70,76]. It is worth noting that there have been only a few experimental and numerical studies conducted to explore how air shear flow influences the droplet dynamics on SHSs [83,84]. In addition, it should be pointed out that when it comes to the impact of micro-scale droplets, the dynamics are different from those at the macro-scale because the surface tension (capillary force) becomes the dominant force over the inertial force.…”

Viscoelastic effects on the deformation and breakup of a droplet on a solid wall in Couette flow

“…2020), degreasing cleaning processes (Yeganehdoust et al. 2021) and cell control in microfluidics (Ye, Shen & Li 2018; Minetti et al. 2019).…”

“…The deformation and motion of a droplet adhering to a solid wall subject to shear flow is a fundamental phenomenon ubiquitous in industrial and biomedical applications, such as enhanced oil recovery (Rock et al 2020), degreasing cleaning processes (Yeganehdoust et al 2021) and cell control in microfluidics (Ye, Shen & Li 2018;Minetti et al 2019). Over the past few decades, a large number of researches have been carried out on such a topic in Newtonian fluid systems.…”