A numerical study on viscoelastic droplet migration on a solid substrate due to wettability gradient

2019 ◽  
Vol 40 (6) ◽  
pp. 851-858
Author(s):  
Fan Bai ◽  
Yuke Li ◽  
Hongna Zhang ◽  
Sang Woo Joo
Keyword(s):  
Numerical Study ◽  
Solid Substrate

Numerical study of the melting and resolidification of the substrate during the impact of a ceramic droplet in a plasma spraying process

2019 ◽  
Vol 88 (2) ◽  
pp. 20901 ◽  
Author(s):  
Mouloud Driouche ◽  
Tahar Rezoug ◽  
Mohammed El Ganaoui
Keyword(s):  
Numerical Model ◽  
Phase Change ◽  
Solid Phase ◽  
Numerical Study ◽  
Solid Substrate ◽  
Navier Stokes ◽  
Droplet Spreading ◽  
Substrate Melting ◽  
Volume Method ◽  
The Impact

The substrate melting can significantly improve the properties of plasma spray coatings. Indeed the adhesion of the projected particles to the substrate can be ameliorated by the substrate melting. In this article, a numerical model is developed to study the dynamics of fluids and heat transfer with liquid/solid phase change during impact of a fully melted alumina particle on an aluminum solid substrate, taking into account of the substrate melting. The model is based on solving the Navier-Stokes and energy equations with liquid / solid phase change. These equations are coupled with the fluid of volume method (VOF), to follow the free surface of the particle during its spreading and solidification. The finite volume method is used to discretize the equations in a 2D axisymmetric domain. A comparison with the published experimental results was carried out to validate this numerical model. Simulations were performed for different initial droplet diameters to study its effect on droplet spreading as well as on substrate melting. It has been observed that the substrate melting begins before the droplet spreads completely; the substrate melting reaches its maximum when the droplet is close to its total solidification. Droplet spreading and substrate melting are more important for large sizes droplets.

A Numerical Study on Hollow Droplets Impact onto a Solid Substrate

2014 ◽  
Vol 852 ◽  
pp. 501-505
Author(s):  
Da Shu Li ◽  
Xing Qi Qiu ◽  
Zhi Wei Zheng
Keyword(s):  
Transfer Rate ◽  
Flat Surface ◽  
Numerical Study ◽  
Solid Substrate ◽  
Hydrodynamic Characteristics ◽  
Air Entrapment ◽  
Deposition Parameters ◽  
Proposed Model ◽  
Gas Cavity ◽  
The Relationship

A numerical model using VOF method is developed to describe the phenomenon of a hollow droplet impact on a flat surface including spreading, retardation, recoil and first and secondary break up. The proposed model is verified by literature experiments. Some new hydrodynamic characteristics have been found. The mechanism of central counter jet is explored according to pressure distribution and velocity vectors inside droplet. The relationship between impact features of droplet and deposition parameters is highlighted. In order to investigate the heat transfer rate at the gas-liquid interface, air entrapment and gas cavity are discussed.

Conjugate Heat Transfer in Single-Phase Wavy Microchannel

2016 ◽  
Author(s):  
Nishant Tiwari ◽  
Manoj Kumar Moharana ◽  
Sunil Kumar Sarangi
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Flow Rate ◽  
Conjugate Heat Transfer ◽  
Numerical Study ◽  
Local Heat Transfer ◽  
Solid Substrate ◽  
Channel Cross Section ◽  
Thermal Conductivity Ratio ◽  
Substrate Thickness

A three-dimensional numerical study has been carried out to understand the effect of axial wall conduction in a conjugate heat transfer situation in a wavy wall square cross section microchannel engraved on solid substrate whose thickness varying between 1.2–3.6 mm. The bottom of the substrate (1.8 × 30 mm2) is subjected to constant wall heat flux while remaining faces exposed to ambient are assumed to be adiabatic. The vertical parallel walls are considered wavy such that the channel cross section at any axial location will be a square (0.6 × 0.6 mm2) and length of the channel is 30 mm. Wavelength (λ) and amplitude (A) of the wavy channel wall are 12 mm and 0.2 mm respectively. Simulations has been carried out for substrate thickness to channel depth ratio (δsf ∼ 1–5), substrate wall to fluid thermal conductivity ratio (ksf ∼ 0.34–646) and flow rate (Re ∼ 100 to 500). The results show that with increase in flow rate (Re), the hydrodynamic and thermal boundary layers are thinned due to wavy passage and they shifted from the centerline towards the peak which improves the local heat transfer coefficient at the solid-fluid interface. It is also found that after attaining maximum Nuavg at optimum ksf, the slope goes downward with increasing ksf for all set of δsf and flow rate (Re) considered in this study.

scholarly journals Numerical Study of a Planar Liquid Jet Impinging on a Solid Substrate

2008 ◽  
Vol 48 (5) ◽  
pp. 603-610 ◽  
Author(s):  
Hitoshi Fujimoto ◽  
Daisuke Ohno ◽  
Takayuki Hama ◽  
Hirohiko Takuda
Keyword(s):  
Numerical Study ◽  
Solid Substrate ◽  
Liquid Jet

scholarly journals Fluctuation assisted spreading of a fluid filled elastic blister

2018 ◽  
Vol 846 ◽  
pp. 1076-1087 ◽  
Author(s):  
Andreas Carlson
Keyword(s):  
Numerical Simulations ◽  
Viscous Flow ◽  
Numerical Study ◽  
Solid Substrate ◽  
Precursor Film ◽  
Scaling Analysis ◽  
Elastic Bending ◽  
Spatially Extended ◽  
Elastic Interface ◽  
Capillary Spreading

In this theoretical and numerical study, we show how spatially extended fluctuations can influence and dominate the dynamics of a fluid filled elastic blister as it deforms onto a pre-wetted solid substrate. To describe the blister dynamics, we develop a stochastic elastohydrodynamic framework that couples the viscous flow, the elastic bending of the interface and the noise from the environment. We deploy a scaling analysis to find the elastohydrodynamic spreading law $\hat{R}\sim \hat{t}^{1/11}$, where $\hat{R}$ is the spreading radius and $\hat{t}$ is time, a direct analogue to the capillary spreading of drops, while the inclusion of noise in our model highlights that the dynamics speeds up significantly $\hat{R}\sim \hat{t}^{1/6}$ as local changes in curvature at the spreading front enhance the peeling of the elastic interface from the substrate. These fluctuations have a pronounced influence on the shape of the deforming blister and lead to the formation of a precursor film similar to a perfectly wetting droplet. Moreover, our analysis identifies a distinct criterion for the transition between the deterministic and the stochastic spreading regime, which is further illustrated by numerical simulations.

Numerical Study of Water Droplet Evaporation on a Superhydrophobic Surface

2013 ◽  
Author(s):  
Zhenhai Pan ◽  
Susmita Dash ◽  
Justin A. Weibel ◽  
Suresh V. Garimella
Keyword(s):  
Contact Angle ◽  
Water Droplet ◽  
Evaporation Rate ◽  
Numerical Study ◽  
Liquid Droplet ◽  
Current Model ◽  
Solid Substrate ◽  
Analytical Models ◽  
Vapor Concentration ◽  
Constant Contact Angle

A comprehensive numerical model is developed to predict evaporation of a water droplet from an unheated superhydrophobic substrate. Analytical models that only consider vapor diffusion in the gas domain, and assume the system to be isothermal, over-predict the evaporation rates by ∼25% compared to experiments conducted on such surfaces. The current model solves for conjugate heat and mass transfer in the solid substrate, liquid droplet, and surrounding gas. Evaporative cooling of the interface is accounted for, and vapor concentration is coupled to local temperature at the interface. Buoyancy-driven convective flows in the droplet and vapor domains are also simulated. A droplet evaporating in a constant-contact-angle mode with an initial volume of 3 μl and contact angle of 160 deg is considered at an ambient temperature of 21°C and 29% relative humidity, to match conditions of related experiments. The interface cooling effect suppresses the evaporation rate significantly; however, natural convection in the gas and liquid domains has a negligible impact on the evaporation rate. The local evaporation flux along the droplet interface predicted by the model is compared to that predicted by an analytical diffusion-based model. The numerically calculated total evaporation rate agrees with experimental results to within 2%. The large deviations between past analytical models and the experimental data on superhydrophobic surfaces are reconciled.

Numerical study of the low-frequency atomic dynamics in a Lennard-Jones glass

1998 ◽  
Vol 77 (2) ◽  
pp. 473-484 ◽  
Author(s):  
M. Sampoli, P. Benassi, R. Dell'Anna,
Keyword(s):  
Numerical Study ◽  
Low Frequency ◽  
Lennard Jones
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