scholarly journals Numerical Bifurcation Analysis of a Film Flowing over a Patterned Surface through Enhanced Lubrication Theory

Fluids ◽  
2021 ◽  
Vol 6 (11) ◽  
pp. 405
Author(s):  
Nicola Suzzi ◽  
Giulio Croce
Keyword(s):  
Contact Angle ◽  
Bifurcation Analysis ◽  
Dynamic Contact Angle ◽  
Flow Characteristics ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Inclined Plate ◽  
Lubrication Equation ◽  
Static Contact ◽  
Numerical Bifurcation

The bifurcation analysis of a film falling down an hybrid surface is conducted via the numerical solution of the governing lubrication equation. Instability phenomena, that lead to film breakage and growth of fingers, are induced by multiple contamination spots. Contact angles up to 75∘ are investigated due to the full implementation of the free surface curvature, which replaces the small slope approximation, accurate for film slope lower than 30∘. The dynamic contact angle is first verified with the Hoffman–Voinov–Tanner law in case of a stable film down an inclined plate with uniform surface wettability. Then, contamination spots, characterized by an increased value of the static contact angle, are considered in order to induce film instability and several parametric computations are run, with different film patterns observed. The effects of the flow characteristics and of the hybrid pattern geometry are investigated and the corresponding bifurcation diagram with the number of observed rivulets is built. The long term evolution of induced film instabilities shows a complex behavior: different flow regimes can be observed at the same flow characteristics under slightly different hybrid configurations. This suggest the possibility of controlling the rivulet/film transition via a proper design of the surfaces, thus opening the way for relevant practical application.

Spreading-Droplet Simulation With Surface Tension Model Using Inter-Particle Force in Particle Method

2013 ◽  
Author(s):  
Eiji Ishii ◽  
Taisuke Sugii
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Dynamic Contact Angle ◽  
Particle Method ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Particle Methods ◽  
Static Contact ◽  
Particle Force ◽  
Surface Tension Model

Predicting the spreading behavior of droplets on a wall is important for designing micro/nano devices used for reagent dispensation in micro-electro-mechanical systems, printing processes of ink-jet printers, and condensation of droplets on a wall during spray forming in atomizers. Particle methods are useful for simulating the behavior of many droplets generated by micro/nano devices in practical computational time; the motion of each droplet is simulated using a group of particles, and no particles are assigned in the gas region if interactions between the droplets and gas are weak. Furthermore, liquid-gas interfaces obtained from the particle method remain sharp by using the Lagrangian description. However, conventional surface tension models used in the particle methods are used for predicting the static contact angle at a three-phase interface, not for predicting the dynamic contact angle. The dynamic contact angle defines the shape of a spreading droplet on a wall. We previously developed a surface tension model using inter-particle force in the particle method; the static contact angle of droplets on the wall was verified at various contact angles, and the heights of droplets agreed well with those obtained theoretically. In this study, we applied our surface tension model to the simulation of a spreading droplet on a wall. The simulated dynamic contact angles for some Weber numbers were compared with those measured by Šikalo et al, and they agreed well. Our surface tension model was useful for simulating droplet motion under static and dynamic conditions.

Effect of Dynamic Contact Angle on Single Bubbles During Nucleate Pool Boiling

2004 ◽  
Author(s):  
Abhijit Mukherjee ◽  
Satish G. Kandlikar
Keyword(s):  
Contact Angle ◽  
Numerical Study ◽  
Removal Rate ◽  
Pool Boiling ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Heated Wall ◽  
Nucleate Pool Boiling ◽  
Static Contact

Nucleate pool boiling at low heat flux is typically characterized by cyclic growth and departure of single vapor bubbles from the heated wall. It has been experimentally observed that the contact angle at the bubble base varies during the ebullition cycle. In the present numerical study, dynamic advancing and receding contact angles obtained from experimental observations are specified at the base of a vapor bubble growing on a wall. The complete Navier-Stokes equations are solved and the liquid-vapor interface is captured using the level-set technique. The effect of dynamic contact angle on the bubble dynamics and vapor removal rate are compared to results obtained with static contact angle. The results show that bubble base exhibits a slip/stick behavior with dynamic contact angle though the overall effect on the vapor removal rate is small. Higher advancing contact angle is found to increase the vapor removal rate.

The Pressure Drop and Dynamic Contact Angle of Motion of Triple-Lines in Hydrophobic Microchannels

2010 ◽  
Author(s):  
Dongin Yu ◽  
Chiwoong Choi ◽  
Moohwan Kim
Keyword(s):  
Contact Angle ◽  
Pressure Drop ◽  
Liquid Film ◽  
Dynamic Contact Angle ◽  
Triple Line ◽  
Dynamic Contact ◽  
Superficial Velocity ◽  
Channel Diameter ◽  
Fluid Property ◽  
Static Contact

At two-phase flow in microchannels, slug flow regime is different for wettability of surface. A slug in a hydrophilic microchannel has liquid film. However, a slug in a hydrophobic microchannel has no liquid film instead, the slug has triple-lines and makes higher pressure drop due to the motion of the triple-line. In previous researches, pressure drop of triple-line is depended of dynamic contact angle, channel diameter and fluid property. And, dynamic contact angle is depended of static contact angle, superficial velocity and fluid property. In order to understand the pressure drop of motion of triple-lines, pressure drop of slug with triple-lines in case of various diameters (0.546, 0.763, 1.018, 1.555, 2.075 mm), various fluids (D.I.water, D.I.water-1, 5, 10% ethanol mixture) and various superficial velocity (j = 0.01∼0.4 m/s) was measured. Dynamic contact angle was calculated from relation of the pressure drop of slug with triple-lines. Comparing with previous dynamic contact angle correlations, previous correlation underestimated dynamic contact angle in the region of this study. (10−4≤Ca≤10−3, 10−2≤We≤10−1, 68°≤θS≤110°)

scholarly journals Numerical Study of Formation of a Series of Bubbles from an Orifice by Applying Dynamic Contact Angle Model

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Nan Chen ◽  
Xiyu Chen ◽  
Antonio Delgado
Keyword(s):  
Contact Angle ◽  
Gas Flow ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Static Contact Angle ◽  
Bubble Shape ◽  
Flow Rates ◽  
Bubble Detachment ◽  
Static Contact ◽  
Detachment Time

The dynamic contact angle model is applied in the formation process of a series of bubbles from Period-I regime to Period-II regime by using the VOF method on a 2D axisymmetric domain. In the first process of the current research, the dynamic contact angle model is validated by comparing the numerical results to the experimental data. Good agreement in terms of bubble shape and bubble detachment time is observed from a lower flow rate Q = 150.8 cm3/min (Re = 54.77, Period-I regime) to a higher flow rate Q = 603.2 cm3/min (Re = 219.07, Period-III regime). The comparison between the dynamic contact angle model and the static contact angle model is also performed. It is observed that the static contact angle model can obtain similar results as the dynamic contact angle model only for smaller gas flow rates (Q ≤ 150.8 cm3/min and Re ≤ 54.77)). For higher gas flow rates, the static contact angle model cannot produce good results as the dynamic contact angle model and has larger relative errors in terms of bubble detachment time and bubble shape.

Level Set Based Modeling of Electrowetting on Dielectrics Droplet

2012 ◽  
Vol 461 ◽  
pp. 138-141
Author(s):  
Yin Xia Chang ◽  
Si Xiang Zhang ◽  
Wei Zhou ◽  
Bao Liu
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Level Set ◽  
Stokes Equations ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Navier Stokes ◽  
Electric Force ◽  
Electrowetting On Dielectric ◽  
Static Contact

This paper discusses the modeling of Electrowetting On Dielectric (EWOD) device that moves fluid droplets through surface tension effects and electric force. Instead of using a static contact angle as most papers did, we take the dynamic contact angle into count by using expression proposed by Voinov and Tanner. Firstly, the level set model and its initial values is present. Then the governing equations are discussed, and the diffused format is adopted for density and viscosity varies to smooth over the interface. The detailed expression for surface tension and electric force are also described for Navier–Stokes equations. After presenting the boundary conditions, the steps of numerical implementation are detailed.

Measurements of the Contact Angles for Various Fluids Which Are Widely Used in the Oilfields to Improve Oil Recovery

2018 ◽  
Author(s):  
M. Elsharafi ◽  
K. Vidal ◽  
R. Thomas
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Interfacial Tension ◽  
Oil Recovery ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Rock Face ◽  
Angle Measurements ◽  
Contact Angle Measurements

Contact angle measurements are important to determine surface and interfacial tension between solids and fluids. A ‘water-wet’ condition on the rock face is necessary in order to extract oil. In this research, the objectives are to determine the wettability (water-wet or oil-wet), analyze how different brine concentrations will affect the wettability, and study the effect of the temperature on the dynamic contact angle measurements. This will be carried out by using the Cahn Dynamic Contact Angle. Analyzer DCA 315 to measure the contact angle between different fluids such as surfactant, alkaline, and mineral oil. This instrument is also used to measure the surface properties such as surface tension, contact angle, and interfacial tension of solid and liquid samples by using the Wilhelmy technique. The work used different surfactant and oil mixed with different alkaline concentrations. Varying alkaline concentrations from 20ml to 1ml were used, whilst keeping the surfactant concentration constant at 50ml.. It was observed that contact angle measurements and surface tension increase with increased alkaline concentrations. Therefore, we can deduce that they are directly proportional. We noticed that changing certain values on the software affected our results. It was found that after calculating the density and inputting it into the CAHN software, more accurate readings for the surface tension were obtained. We anticipate that the surfactant and alkaline can change the surface tension of the solid surface. In our research, surfactant is desirable as it maintains a high surface tension even when alkaline percentage is increased.

Hydrosilation-Cured Poly(dimethylsiloxane) Networks:  Intrinsic Contact Angles via Dynamic Contact Angle Analysis

2003 ◽  
Vol 36 (10) ◽  
pp. 3689-3694 ◽  
Author(s):  
Janelle M. Uilk ◽  
Ann E. Mera ◽  
Robert B. Fox ◽  
Kenneth J. Wynne
Keyword(s):  
Contact Angle ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Contact Angle Analysis

Effect of Nanometer Far-Infrared Materials on the Cleanability of Ceramic Glazes

2010 ◽  
Vol 178 ◽  
pp. 103-108
Author(s):  
Li Juan Wang ◽  
Jin Sheng Liang ◽  
Wen Bo Xu ◽  
Dao Yang Han
Keyword(s):  
Contact Angle ◽  
Free Energy ◽  
Oleic Acid ◽  
Surface Free Energy ◽  
Dynamic Contact Angle ◽  
Far Infrared ◽  
Dynamic Contact ◽  
Interface Tension ◽  
Static Contact ◽  
Infrared Materials

Nanometer far-infrared materials (NFIM) were doped into ceramic glazes to prepare easy-to-clean ceramic glazes，and the effect of NFIM on the cleanability properties was investigated. Static contact angle measurements were used to describe the surface hydrophilic property and calculate the surface free energy. The effect of far-infrared radiance measured by Fourier Transform Infrared Spectrometer on the O/W interface tension was tested by a Dynamic Contact Angle Meter and Tensiometer. The cleanability was estimated by the ultraviolet spectrophotometry technique using oleic acid as soiling agent. It was shown that the better cleanability of the ceramic glazes, the higher surface free energy and its polar contribution. The experiments were carried out on detachment of oleic acid drop from the easy-to-clean ceramic glazes. The three-phase contact line shrinked spontaneously, and eventually the oil drop detached from the surface. The spontaneous detachment of a drop corresponded to two different driving factors: (1) the decrease of oil-water interfacial tension caused by the far-infrared radiation of the glazes, (2) the spontaneous advancement of aqueous meniscus owing to the penetration of water between the oil and super hydrophilic glaze surfaces.

scholarly journals Hydrodynamic Study of an Oscillating Meniscus in a Square Mini-Channel

2009 ◽  
Author(s):  
Yajuvendra Singh Shekhawat ◽  
Sameer Khandekar ◽  
Pradipta Kumar Panigrahi
Keyword(s):  
Contact Angle ◽  
High Speed ◽  
Capillary Tube ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Glass Capillary ◽  
Two Fluids ◽  
Silicon Oil ◽  
Static Contact ◽  
Micro Systems

Miniaturized fluidic systems like MEMS may involve single-phase or multi-phase flows with oscillations/ pulsations. Understanding the hydrodynamics of such flows can help in manipulating the performance parameters and improving the efficiency of micro-systems. This work focuses on hydrodynamics of a sinusoidally oscillating meniscus in a square mini-channel. The interfacial contact line behavior of a single oscillating meniscus formed between liquid slug and air, inside the square capillary tube, has been explored. An eccentric cam follower system has been fabricated to provide sinusoidal oscillations of fluid in the square glass capillary having hydraulic diameter of 2.0 mm. Experiments are conducted with two fluids, water and silicon oil. Dynamic contact angle measurements are carried out for water at two oscillating frequencies, 0.25 Hz and 0.50 Hz using high speed videography. It is seen that an increase in the oscillating frequency increases the difference in the advancing angle and receding angle of the meniscus, with the static contact angle of water on glass surface around 21°. For silicon oil the experiments have been performed at eight different frequencies in the range of 0.20 Hz and 1.00 Hz. It is seen that the meniscus is pinned at the extreme end of the stroke, unlike that in the case of water, and there is a film of silicon oil during oscillations. The thickness of the film formed increases with increase in oscillating frequency. There is considerable difference in the hydrodynamics of silicon oil and water.

Effects of Wettability on Capillary Flow of Non-Newtonian Fluid in Microchannels

2018 ◽  
Author(s):  
Kiarash Keshmiri ◽  
Neda Nazemifard ◽  
Haibo Huang
Keyword(s):  
Contact Angle ◽  
Capillary Flow ◽  
Dynamic Contact Angle ◽  
Propagation Distance ◽  
Dynamic Contact ◽  
Water Contact ◽  
Capillary Filling ◽  
Static Contact ◽  
Constant Contact Angle ◽  
Theoretical Results

In this study, capillary filling of diluted bitumen was evaluated using glass etched microchannel. Glass microchannel was treated using Trichloro(1H,1H,2H,2H-perfluorooctyl) silane that makes the microchannel lyophobic (not favorable for neither hydrophilic nor hydrophobic liquids). Water contact angle, as a degree of hydrophilicity, was changed from 15° for untreated microchannel to 115° for treated microchannel. Measured Capillary filling speed of bitumen in hexane (10% to 60%) was experimentally monitored using white light microscope and compared with Washburn theoretical model. For all samples, a linear relation between square of propagation distance and time was found. However, a deviation between experimental and theoretical values of penetration as a function of time was recorded. Experimental results indicated slower velocity compared to theoretical prediction due to simplifications of the Washburn model. Advancing dynamic contact angle of capillary-driven flow was measured and compared with static contact angle using MATLAB®. It was found that dynamic contact angle was increasing during the penetration in microchannel and application of a constant contact angle leads to higher deviation between experimental and theoretical results.

Sign in / Sign up

Export Citation Format

Share Document