Shear Driven Droplet Shedding on Surfaces with Various Wettabilities

Moghtadernejad, Sara; Mohammadi, Morteza; Jadidi, Majid; Tembely, Moussa; Dolatabadi, Ali

doi:10.4271/2013-01-2176

Cited by 45 publications

(18 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…There are various unique properties related to fine microstructured coatings such as enhanced catalytic behavior, noticeable superhydrophobicity [104][105][106][107][108][109][110][111] behavior, remarkable wear resistance, superior thermal insulation and thermal shock resistance [7,[112][113][114]. Nevertheless, coating fine particles using conventional atmospheric thermal spray techniques is a difficult task to do due to several reasons.…”

Section: High Velocity Suspension Flame Spray (Hvsfs) Techniquementioning

confidence: 99%

A Comprehensive Review on Fluid Dynamics and Transport of Suspension/Liquid Droplets and Particles in High-Velocity Oxygen-Fuel (HVOF) Thermal Spray

2015

Self Cite

View full text Add to dashboard Cite

Abstract:In thermal spraying processes, molten, semi-molten, or solid particles, which are sufficiently fast in a stream of gas, are deposited on a substrate. These particles can plastically deform while impacting on the substrate, which results in the formation of well-adhered and dense coatings. Clearly, particles in flight conditions, such as velocity, trajectory, temperature, and melting state, have enormous influence on the coating properties and should be well understood to control and improve the coating quality. The focus of this study is on the high velocity oxygen fuel (HVOF) spraying and high velocity suspension flame spraying (HVSFS) techniques, which are widely used in academia and industry to generate different types of coatings. Extensive numerical and experimental studies were carried out and are still in progress to estimate the particle in-flight behavior in thermal spray processes. In this review paper, the fundamental phenomena involved in the mentioned thermal spray techniques, such as shock diamonds, combustion, primary atomization, secondary atomization, etc., are discussed comprehensively. In addition, the basic aspects and emerging trends in simulation of thermal spray processes are reviewed. The numerical approaches such as Eulerian-Lagrangian and volume of fluid along with their advantages and disadvantages are explained in detail. Furthermore, this article provides a detailed review on simulation studies published to date. OPEN ACCESSCoatings 2015, 5 577

show abstract

Section: High Velocity Suspension Flame Spray (Hvsfs) Techniquementioning

confidence: 99%

A Comprehensive Review on Fluid Dynamics and Transport of Suspension/Liquid Droplets and Particles in High-Velocity Oxygen-Fuel (HVOF) Thermal Spray

2015

Self Cite

View full text Add to dashboard Cite

show abstract

“…However, as the drag and lift forces resulting from 5 m/s of air speed are not high enough to overcome gravity, the droplet comes back to the surface at t = 83 ms. Hence, for the low speed of 5 m/s, unlike the single droplet case shown in the work of Moghtadernejad et al 20 that the coalesced droplet only rolls on the superhydrophobic plate, in the two droplets case, the coalesced droplet detaches from the surface and consequently lands on the substrate.…”

Section: A Droplet Coalescence At Low Speedmentioning

confidence: 85%

“…(21) and (22), variations of t * versus Reynolds number are plotted in Figure 17. In addition in this figure, dimensionless detachment time of a single droplet shedding presented in the authors' previous work 20,21 versus Reynolds number is compared with those of the case with two droplets presented in this paper.…”

Section: B Droplet Coalescence At High Speedmentioning

confidence: 98%

“…In contrast, increasing the detachment time of foliar fertilizers from superhydrophobic leafs enhances the fertilizer's adsorption ratio. The same approach used in the work of Moghtadernejad et al 20,21 is applied here to investigate the air speed effect on the coalesced droplet detachment time from the superhydrophobic surface, the detail of which is given in the following paragraphs. where R o is the initial radius of the droplet before the deposition on the substrate and θ is the static contact angle of the droplet on the superhydrophobic surface.…”

Section: B Droplet Coalescence At High Speedmentioning

confidence: 99%

“…Milne and Amirfazli 6 investigated the incipient motion of single droplet under the effect of air flows as high as 30 m/s on different surface wettabilities. To address the effect of higher air speeds, Moghtadernejad et al 20 performed the single droplet shedding analysis on hydrophilic and superhydrophobic substrates with air speeds as high as 90 m/s. Despite the above mentioned studies, the coalescence of droplets under the effect of air flow is still a questionable topic.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Shear driven droplet shedding and coalescence on a superhydrophobic surface

et al. 2015

View full text Add to dashboard Cite

Turbulence and skin friction modification in channel flow with streamwise-aligned superhydrophobic surface texture Phys. Fluids 26, 095102 (2014); 10.1063/1.4894064 Numerical exploration of the origin of aerodynamic enhancements in [low-Reynolds number] corrugated airfoils A mechanism for unsteady separation in over-expanded nozzle flowThe interest on shedding and coalescence of sessile droplets arises from the importance of these phenomena in various scientific problems and industrial applications such as ice formation on wind turbine blades, power lines, nacelles, and aircraft wings. It is shown recently that one of the ways to reduce the probability of ice accretion on industrial components is using superhydrophobic coatings due to their low adhesion to water droplets. In this study, a combined experimental and numerical approach is used to investigate droplet shedding and coalescence phenomena under the influence of air shear flow on a superhydrophobic surface. Droplets with a size of 2 mm are subjected to various air speeds ranging from 5 to 90 m/s. A numerical simulation based on the Volume of Fluid method coupled with the Large Eddy Simulation turbulent model is carried out in conjunction with the validating experiments to shed more light on the coalescence of droplets and detachment phenomena through a detailed analysis of the aerodynamics forces and velocity vectors on the droplet and the streamlines around it. The results indicate a contrast in the mechanism of two-droplet coalescence and subsequent detachment with those related to the case of a single droplet shedding. At lower speeds, the two droplets coalesce by attracting each other with successive rebounds of the merged droplet on the substrate, while at higher speeds, the detachment occurs almost instantly after coalescence, with a detachment time decreasing exponentially with the air speed. It is shown that coalescence phenomenon assists droplet detachment from the superhydrophobic substrate at lower air speeds. C 2015 AIP Publishing LLC.

show abstract

Effect of thermo‐oxidative aging on surface characteristics of benzoxazine and epoxy copolymer

Moghtadernejad

Barjasteh

Johnson

et al. 2020

J of Applied Polymer Sci

Self Cite

View full text Add to dashboard Cite

The copolymer of bisphenol A‐based benzoxazine and cycloaliphatic epoxy resin possesses greater processability and glass‐transition temperature compared to that of benzoxazine homopolymer, making it suitable for high‐temperature aerospace applications. The aim of this work is to investigate the behavior of the copolymers under thermos‐oxidative aging conditions using the surface characterization techniques. The benzoxazine homopolymer and copolymer samples were thermally aged in an air‐circulating oven under controlled temperatures of 180 and 200°C for various periods of time up to 24 weeks. The thermo‐oxidative‐induced weight change and surface cracking were monitored for samples during the aging period. As an alternative method to characterize thermal aging, static contact angle, and contact angle hysteresis of samples were measured over time. Moreover, droplet impact tests using deionized water were performed on stationary and moving samples to investigate the effects of aging time and temperature on impact dynamics of droplets. In addition, FTIR analysis was performed to evaluate the chemical changes on the surface of samples. The results indicated the extent of degradation of aged samples increased with increasing the aging time and temperature. In addition, the copolymer of cycloaliphatic epoxy and benzoxazine showed a greater amount of thermos‐oxidative degradation than the one for benzoxazine homopolymer. More importantly, the results obtained from the surface analysis measurements (e.g., contact angle) followed a similar trend to the one obtained from the traditional aging experiments (e.g., weight change). This showed the former nondestructive and simple method can be used to monitor thermal aging of materials in service.

show abstract

Shear Driven Droplet Shedding on Surfaces with Various Wettabilities

Cited by 45 publications

References 4 publications

A Comprehensive Review on Fluid Dynamics and Transport of Suspension/Liquid Droplets and Particles in High-Velocity Oxygen-Fuel (HVOF) Thermal Spray

A Comprehensive Review on Fluid Dynamics and Transport of Suspension/Liquid Droplets and Particles in High-Velocity Oxygen-Fuel (HVOF) Thermal Spray

Shear driven droplet shedding and coalescence on a superhydrophobic surface

Effect of thermo‐oxidative aging on surface characteristics of benzoxazine and epoxy copolymer

Contact Info

Product

Resources

About