Numerical Simulation of Droplet Impact on an Isothermal Micro-Grooved Solid Surface

2010 ◽  
Author(s):  
Yujia Tao ◽  
Xiulan Huai ◽  
Zhigang Li
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Solid Surface ◽  
Initial Velocity ◽  
Surface Tension Coefficient ◽  
Liquid Region ◽  
Spreading Factor ◽  
Droplet Spreading ◽  
Droplet Dynamics ◽  
The Impact

The process of a micro droplet of distilled water impact on an isothermal micro-grooved solid surface is numerical simulated in this paper. To accurately represent the droplet dynamics, special attention is given to the variation of the droplet pressure and velocity, the movement of the free surface between two fluids and the deforming of the droplet after impact. The Volume Of Fluid method is used to track the position and the shape of the liquid region. The PISO algorithm is selected to solve the pressure-velocity coupling. The influences of the droplet initial velocity, the contact angle for water on the surface perpendicular to the groove direction and the surface tension coefficient on the impact process are discussed in detail. The results show that the droplet spreading factor improves notably with the increase of the initial velocity, and reduces with the increase of the contact angle. When the surface tension coefficient increases, the spreading factor reduces greatly. The spreading factor is the largest and the time elapsing is the longest in the case of σ = 0.038 N/m.

scholarly journals The effects of surface tension on the spreading ratio during the impact of multiple droplets onto a hot solid surface

2018 ◽  
Vol 197 ◽  
pp. 08016
Author(s):  
Rafil Arizona ◽  
Teguh Wibowo ◽  
Indarto Indarto ◽  
Deendarlianto Deendarlianto
Keyword(s):  
Surface Tension ◽  
Ethylene Glycol ◽  
Solid Surface ◽  
High Speed ◽  
Frame Rate ◽  
Stainless Steel Surface ◽  
Droplet Spreading ◽  
Secondary Droplets ◽  
The Impact ◽  
Maximum Spreading

The impact between multiple droplets onto hot surface is an important process in a spray cooling. The present study was conducted to investigate the dynamics of multiple droplet impact under various surface tensions. Here, the ethylene glycol with compositions of 0%, 5%, and 15% was injected through a nozzle onto stainless steel surface as the multiple droplet. The solid surface was heated at the temperatures of 100 °C, 150 °C, and 200 °C. To observe the dynamics of multiple droplets, a high speed camera with the frame rate of 2000 fps was used. A technique of image processing was developed to determine the maximum droplet spreading ratio. As the result, the surface tension contributes significantly to maximum spreading ratio. As the droplet surface tension decreases, the maximum spreading ratio increases. The maximum spreading ratio appears when the percentage of the ethylene glycol is 15% at the temperature of 150°C. From the visual observation, it is shown that a slower emergence of secondary droplets (droplet splashing) is carried out under a lower surface tension. Hence, surface tension plays an important role on the behavior of emerging secondary droplets. Furthermore, results of the experiments are useful for the validation of available previous CFD models.

Effect of Dynamic Contact Angle on Single/Successive Droplet Impingement

2007 ◽  
Author(s):  
S. Sangplung ◽  
J. A. Liburdy
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Solid Surface ◽  
Contact Line ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Droplet Impingement ◽  
Spreading Velocity ◽  
Fluid Properties ◽  
The Impact

Successive droplet impingement onto a solid surface is numerically investigated using a CFD multiphase flow model (VOF method). The main focus of this study is to better understand the hydrodynamics of the non-splash impingement process, particularly the effect of a dynamic contact angle and fluid properties along with the interaction between successive droplets while they are impinging onto a solid surface. The pre-impact droplet conditions are prescribed based on a spherical droplet diameter, velocity, and inter-droplet spacing. The molecular kinetic theory is used to model the dynamic contact angle as a function of a contact line velocity. The numerical scheme is validated against experiment results. In the impact spreading and receding processes, results are analyzed to determine the nondimensional deformation characteristics of both single and successive droplet impingements with the variation of fluid properties such as surface tension and dynamic viscosity. These characteristics include spreading ratio, spreading velocity, and a dynamic contact angle. The inclusion of a dynamic contact angle is shown to have a major effect on droplet spreading. In successive droplet impingement, the second drop causes a surge of spreading velocity and contact angle with an associate complex recirculating flow near the contact line after it initially impacts the preceding droplet when it is in an advancing condition. This interaction is less dramatic when the first drop is receding or stationary. The surface tension has the most effect on the maximum spreading radius in both single and successive droplet impingements. In contrast to this, the viscosity directly affects the damping of the spreading-receding process.

scholarly journals Numerical Simulations of the Impact and Spreading of a Particulate Drop on a Solid Substrate

2012 ◽  
Vol 2012 ◽  
pp. 1-10
Author(s):  
Hyun Jun Jeong ◽  
Wook Ryol Hwang ◽  
Chongyoup Kim
Keyword(s):  
Numerical Simulations ◽  
Solid Surface ◽  
Reynolds Numbers ◽  
Suspended Particles ◽  
Solid Substrate ◽  
Oscillatory Behavior ◽  
Navier Stokes ◽  
Droplet Spreading ◽  
Navier Stokes Equation ◽  
The Impact

We present two-dimensional numerical simulations of the impact and spreading of a droplet containing a number of small particles on a flat solid surface, just after hitting the solid surface, to understand particle effects on spreading dynamics of a particle-laden droplet for the application to the industrial inkjet printing process. The Navier-Stokes equation is solved by a finite-element-based computational scheme that employs the level-set method for the accurate interface description between the drop fluid and air and a fictitious domain method for suspended particles to account for full hydrodynamic interaction. Focusing on the particle effect on droplet spreading and recoil behaviors, we report that suspended particles suppress the droplet oscillation and deformation, by investigating the drop deformations for various Reynolds numbers. This suppressed oscillatory behavior of the particulate droplet has been interpreted with the enhanced energy dissipation due to the presence of particles.

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.

Experimental Investigation of Droplet Dynamics on Solid Surfaces: Spreading and Recoil Effects

2006 ◽  
Author(s):  
Kalpak P. Gatne ◽  
Milind A. Jog ◽  
Raj M. Manglik
Keyword(s):  
Surface Tension ◽  
High Speed ◽  
Lower Surface ◽  
Video Camera ◽  
Temporal Variations ◽  
Liquid Viscosity ◽  
Viscous Effects ◽  
Droplet Dynamics ◽  
Digital Video Camera ◽  
The Impact

A study of the normal impact of liquid droplets on a dry horizontal substrate is presented in this paper. The impact dynamics, spreading and recoil behavior are captured using a high-speed digital video camera at 2000 frames per second. A digital image processing software was used to determine the drop spread and height of the liquid on the surface from each frame. To ascertain the effects of liquid viscosity and surface tension, experiments were conducted with four liquids (water, ethanol, propylene glycol and glycerin) that have vastly different fluid properties. Three different Weber numbers (20, 40, and 80) were considered by altering the height from which the drop is released. The high-speed photographs of impact, spreading and recoil are shown and the temporal variations of dimensionless drop spread and height are provided in the paper. The results show that changes in liquid viscosity and surface tension significantly affect the spreading and recoil behavior. For a fixed Weber number, lower surface tension promotes greater spreading and higher viscosity dampens spreading and recoil. Using a simple scale analysis of energy balance, it was found that the maximum spread factor varies as Re1/5 when liquid viscosity is high and viscous effects govern the spreading behavior.

Some remarks on the solid surface tension determination from contact angle measurements

2017 ◽  
Vol 405 ◽  
pp. 88-101 ◽  
Author(s):  
Anna Zdziennicka ◽  
Katarzyna Szymczyk ◽  
Joanna Krawczyk ◽  
Bronisław Jańczuk
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Solid Surface ◽  
Angle Measurements ◽  
Contact Angle Measurements ◽  
Solid Surface Tension

scholarly journals Влияние поверхностного натяжения на разрушение макрообъема жидкости при его свободном падении

2020 ◽  
Vol 46 (3) ◽  
pp. 31
Author(s):  
В.А. Архипов ◽  
С.А. Басалаев ◽  
Н.Н. Золоторёв ◽  
К.Г. Перфильева ◽  
А.С. Усанина
Keyword(s):  
Experimental Study ◽  
Surface Tension ◽  
Initial Velocity ◽  
Surface Tension Coefficient ◽  
Initial Volume ◽  
Complete Destruction ◽  
Core Volume

The technique and results of an experimental study of the effect of the surface tension coefficient and the initial volume of a water core on the dynamics of its destruction at free settling in air with a non-zero initial velocity are presented. It is shown that the distance over which the water core completely collapses with the formation of the cloud of droplets decreases by 30% at two-fold decrease in the surface tension coefficient of a liquid. It is shown that the dependence of distance of complete destruction on the initial core volume has a minimum.

Droplet Impacting on a Hydrophobic Surface: Influence of Surface Wetting State on Droplet Behavior

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Abba Abdulhamid Abubakar ◽  
Bekir Sami Yilbas ◽  
Ghassan Hassan ◽  
Hussain Al-Qahtani ◽  
Haider Ali ◽  
...  
Keyword(s):  
Contact Angle ◽  
Hydrophobic Surface ◽  
Transition Time ◽  
Restitution Coefficient ◽  
Surface Wetting ◽  
Local Pressure ◽  
Droplet Spreading ◽  
Droplet Dynamics ◽  
Droplet Shape ◽  
Droplet Behavior

Abstract Water droplet impacting onto a hydrophobic surface is considered and the influence of the surface wetting state on the droplet dynamics is examined. Pressure variation in the impacting droplet is predicted numerically using the level set model. The droplet spreading and the retraction on the hydrophobic surface are assessed for various wetting states of the hydrophobic surface. Experiment is carried out to validate the predictions of the droplet shape and the restitution coefficient. It is found that predictions of impacting droplet shape and the restitution coefficient agree with those obtained from the experiment. The local pressure peaks formed in the droplet fluid, particularly in the retraction period, causes alteration of the droplet vertical height and the shape. Droplet spreading is influenced by the wetting state of the hydrophobic surface; hence, increasing contact angle of the hydrophobic surface lowers the spreading diameter of the droplet on the surface. The transition time of the droplet changes with the wetting state of the hydrophobic surface such that increasing droplet contact angle reduces the transition time of the droplet on the surface. The droplet remains almost round after the first bounding for large contact angle hydrophobic surface.

Investigation of Bubble Nucleation on Platinum Solid Surface Using Molecular Dynamics (MD) Simulation

2010 ◽  
Author(s):  
S. M. Mirnouri Langroudi ◽  
M. Ghasemi ◽  
A. Shahabi ◽  
H. Rezaei Nejad
Keyword(s):  
Molecular Dynamics ◽  
Surface Tension ◽  
Contact Angle ◽  
Solid Surface ◽  
Bubble Radius ◽  
Pair Potential ◽  
Computer Code ◽  
Bubble Nucleation ◽  
Solid Surfaces ◽  
Density Profiles

The main purpose of this paper is to numerically investigate the contact angle of a bubble on a solid surface and the effect of bubble curvature on the surface tension. A computer code based on Molecular Dynamics method is developed. The code carries out a series of simulations to generate bubbles between two planar solid surfaces for different wettabilities. In our simulation, the surface wettability affects the bubble contact angle and curvature. The pair potential for the liquid–liquid and liquid-solid interaction is considered using Lennard-Jones model. Density profiles are locally calculated. Furthermore, surface tension is computed using Young-Laplace equation. It is observed that the gas pressure is independent of the bubble radius. However, the liquid pressure becomes more negative as the radius decreases. In addition, the amount of surface tension decreases by decrease of the radius.

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