Effects of Various Parameters on the Coating of Substrates with Trenches

2012 ◽  
Vol 569 ◽  
pp. 219-222
Author(s):  
Ali Mazloomi ◽  
Ali Moosavi
Keyword(s):  
Contact Angle ◽  
Lattice Boltzmann ◽  
Capillary Number ◽  
Close Agreement ◽  
Critical Size ◽  
Thin Liquid Film ◽  
Film Coating ◽  
Contact Angles ◽  
Critical Depth ◽  
Boltzmann Method

We investigate thin liquid film coating of substrates with trenches via lattice Boltzmann method. The effects of different parameters such as the capillary number, the contact angles and geometric parameters on the results are studied. Our results indicate that for trench depths greater than a critical size coating of the trench is not successful. The critical depth increases by decreasing the capillary number. Moreover we find height, width, capillary number and contact angle under which the coating is successful. The results have been compared with the available results and very close agreement has been achieved.

scholarly journals Contact angle measurement in lattice Boltzmann method

2018 ◽  
Vol 76 (7) ◽  
pp. 1686-1698 ◽  
Author(s):  
Binghai Wen ◽  
Bingfang Huang ◽  
Zhangrong Qin ◽  
Chunlei Wang ◽  
Chaoying Zhang
Keyword(s):  
Contact Angle ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Contact Angle Measurement ◽  
Angle Measurement ◽  
Boltzmann Method

The Effect of Surface Wettability on Viscous Film Deposition

2009 ◽  
Author(s):  
Alexandru Herescu ◽  
Jeffrey S. Allen
Keyword(s):  
Contact Angle ◽  
Film Thickness ◽  
Capillary Number ◽  
High Speed ◽  
Glass Tube ◽  
Contact Angles ◽  
Film Deposition ◽  
Surface Wettability ◽  
Working Fluid ◽  
Uniqueness Of The Solution

The viscous deposition of a liquid film on the inside of a capillary has been experimentally investigated with a focus on the relationship between the film thickness and surface wettability. With distilled water as a working fluid tests were run in a 622 microns diameter glass tube with contact angles of 30° and 105°, respectively. In the first set of experiments the tube was uncoated while in the second set a fluoropolymer coating was applied to increase the contact angle. A film thickness dependence with the contact angle θ (surface wettability) as well as the Capillary number in the form hR ∼ Ca2/3/cosθ is inferred from scaling arguments. For partial wetting it may explain the existence of a thicker film for nonzero contact angle. It was further found that the non-wetting case of 105° contact angle deviates significantly from the existing theories, the film thickness presenting a weak dependence with the Capillary number. This deviation as well as the apparent non-uniqueness of the solution is thought to be caused by the film instability (rupture) observed during the tests. The thickness of the deposited film as a function of the Capillary number was estimated from the liquid mass exiting the capillary and the gas-liquid interface (meniscus) velocity, and compared to Bretherton’s data and a correlation proposed by Quere. The film thickness measurements as well as the meniscus velocity were determined with the aid of a Photron high speed camera with 10000 frames per second sampling capability coupled with a Nikon TE-2000 inverted microscope and a Precisa electronic balance.

scholarly journals Droplet spreading and permeating on the hybrid-wettability porous substrates: a lattice Boltzmann method study

Open Physics ◽  
2016 ◽  
Vol 14 (1) ◽  
pp. 483-491 ◽  
Author(s):  
Wen-Kai Ge ◽  
Gui Lu ◽  
Xin Xu ◽  
Xiao-Dong Wang
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Droplet Spreading ◽  
Small Surface ◽  
Pore Sizes ◽  
Fluid Properties ◽  
Boltzmann Method ◽  
Porous Substrates

AbstractThe spreading and permeation of droplets on porous substrates is a fundamental process in a variety of applications, such as coating, dyeing, and printing. The spreading and permeating usually occur synchronously but play different roles in the practical applications. The mechanisms of the competition between spreading and permeation is significant but still unclear. A lattice Boltzmann method is used to study the spreading and permeation of droplets on hybrid-wettability porous substrates, with different wettability on the surface and the inside pores. The competition between the spreading and the permeation processes is studied in this work from the effects of the substrate and the fluid properties, including the substrate wettability, the porous parameters, as well as the fluid surface tension and viscosity. The results show that increasing the surfacewettability and the porosity contact angle both inhibit the spreading and the permeation processes. When the inside porosity contact angle is larger than 90° (hydrophobic), the permeation process does not occur. The droplets suspend on substrates with Cassie state. The droplets are more easily to permeate into substrates with a small inside porosity contact angle (hydrophilic), as well as large pore sizes. Otherwise, the droplets are more easily to spread on substrate surfaces with small surface contact angle (hydrophilic) and smaller pore sizes. The competition between droplet spreading and permeation is also related to the fluid properties. The permeation process is enhanced by increasing of surface tension, leading to a smaller droplet lifetime. The goals of this study are to provide methods to manipulate the spreading and permeation separately, which are of practical interest in many industrial applications.

scholarly journals The application of computational fluid dynamics to the modelling and design of high-speed boats

2021 ◽  
Author(s):  
◽  
Jack Townsend
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Lattice Boltzmann ◽  
High Speed ◽  
Close Agreement ◽  
Navier Stokes ◽  
Industry Data ◽  
Dynamic Optimisation ◽  
Evolutionary Optimisation ◽  
Boltzmann Method

Computational fluid dynamics solvers were applied to the field of high-speed boat design. The lattice Boltzmann method was used to assess the water-phase of the flow around a number of high-speed hullform geometries, and was validated against empirical industry and literature data. A heave dynamics capability was developed to assess the heave equilibrium position of a high speed boat, showing close agreement with industry data. A mesh movement and evolutionary optimisation software was applied to the aero-dynamic optimisation of a high-speed catamaran using a Reynolds-averaged Navier-Stokes solver for modelling of the air phase of the flow.

scholarly journals Color-gradient lattice Boltzmann modeling of immiscible two-phase flows on partially wetting surfaces

2017 ◽  
Vol 232 (3) ◽  
pp. 416-430 ◽  
Author(s):  
Yuan Yu ◽  
Haihu Liu ◽  
Yonghao Zhang ◽  
Dong Liang
Keyword(s):  
Lattice Boltzmann ◽  
Capillary Number ◽  
Viscosity Ratio ◽  
High Viscosity ◽  
Contact Angles ◽  
Displacement Velocity ◽  
Two Dimensional ◽  
Change Rate ◽  
Finger Length ◽  
Color Gradient

A zero-interfacial-force condition is derived and implemented to improve the wetting boundary scheme for a lattice Boltzmann color-gradient model. This new wetting boundary scheme is validated by two static problems, i.e. a droplet resting on a flat surface and a cylindrical surface, and one dynamic problem, i.e. the capillary filling in a two-dimensional channel. In these simulations, we observe that non-physical mass transfer is suppressed and spurious velocities become smaller. Meanwhile, accurate results including dynamic contact line movement are achieved for a broad range of contact angles. The model is then applied to study the displacement of immiscible fluids in a two-dimensional channel. Both the displacement velocity and the change rate of finger length are found to exhibit a linear dependence on the contact angle at the viscosity ratio of unity. The displacement velocity decreases but the change rate of finger length increases with increasing capillary number, while the displacement velocity tends to be constant, i.e. two-thirds of the maximum inlet velocity, at high viscosity ratios or low capillary numbers. In contrast to the displacement velocity, the change rate of finger length is negligible at high viscosity ratios or low capillary numbers, where the finger length is in an equilibrium state, while the equilibrium finger length itself is smaller at a higher viscosity ratio or a lower capillary number.

Numerical Studies of Stretching Liquid Bridges Between Two Spherical Solid Particles With Different Contact Angles

2010 ◽  
Author(s):  
Pirooz Darabi ◽  
Konstantin Pougatch ◽  
Martha Salcudean ◽  
Dana Grecov
Keyword(s):  
Contact Angle ◽  
Capillary Number ◽  
Contact Angles ◽  
Solid Particles ◽  
Spherical Particles ◽  
Liquid Bridges ◽  
Liquid Distribution ◽  
Liquid Transfer ◽  
Static Conditions ◽  
Rupture Distance

Numerical simulations of the governing Navier-Stokes equations are used to predict the rupture and liquid distribution of stretching liquid bridges between two equal-sized solid spherical particles with different liquid-solid contact angles. A commercial computational fluid dynamics (CFD) tool — FLUENT — is used. The effects of the capillary number and contact angle on the rupture distance and liquid transfer fraction are studied. The simulation results show that for particles with different contact angles, the rupture distance increases as the capillary number is increased; this is similar to the case of particles with identical contact angles. Also, it is shown that for quasi-static conditions, the rupture distance decreases as the difference between the contact angles is increased. Plots of the variations of the liquid transfer fraction with respect to the capillary number show three zones: (1) for high capillary numbers, liquid is almost equally distributed (dynamic zone); (2) for low capillary numbers, the liquid transfer fraction depends on the contact angles and more liquid is transferred to the particle with the smaller contact angle (quasi-static zone); (3) at intermediate capillary numbers, the curve connecting the above limiting conditions resembles an S-shape (transition zone), showing the dependency of the liquid distribution on both capillary number and contact angles. The trends are consistent with the experimental findings published in the literature.

Lattice Boltzmann simulation of immiscible displacement in the cavity with different channel configurations

2017 ◽  
Vol 28 (11) ◽  
pp. 1750136 ◽  
Author(s):  
Qin Lou ◽  
Chenqiang Zang ◽  
Mo Yang ◽  
Hongtao Xu
Keyword(s):  
Surface Roughness ◽  
Contact Angle ◽  
Lattice Boltzmann ◽  
Contact Angles ◽  
Surface Wettability ◽  
Immiscible Displacement ◽  
Displacement Efficiency ◽  
Small Contact Angle ◽  
Gas Cavity ◽  
Pseudo Potential

In this work, the immiscible displacement in a cavity with different channel configurations is studied using an improved pseudo-potential lattice Boltzmann equation (LBE) model. This model overcomes the drawback of the dependence of the fluid properties on the grid size, which exists in the original pseudo-potential LBE model. The approach is first validated by the Laplace law. Then, it is employed to study the immiscible displacement process. The influences of different factors, such as the surface wettability, the distance between the gas cavity and liquid cavity and the surface roughness of the channel are investigated. Numerical results show that the displacement efficiency increases and the displacement time decreases with the increase of the surface contact angle. On the other hand, the displacement efficiency increases with increasing distance between the gas cavity and the liquid cavity at first and finally reaches a constant value. As for the surface roughness, two structures (a semicircular cavity and a semicircular bulge) are studied. The comprehensive results show that although the displacement processes for both the structures depend on the surface wettability, they present quite different behaviors. Specially, for the roughness structure constituted by the semicircular cavity, the displacement efficiency decreases and displacement time increases evidently with the size of the semicircular cavity for the small contact angle. The trend slows down as the increase of the contact angle. Once the contact angle exceeds a certain value, the size of the semicircular cavity almost has no influence on the displacement process. While for the roughness structure of a semicircular bulge, the displacement efficiency increases with the size of bulge first and then it decreases for the small contact angle. The displacement efficiency increases first and finally reaches a constant for the large contact angle. The results also show that the displacement time has an extreme value in these cases for the small contact angles.

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