On an averaged model for immiscible two‐phase flow with surface tension and dynamic contact angle in a thin strip

2021 ◽  
Author(s):  
Stephan B. Lunowa ◽  
Carina Bringedal ◽  
Iuliu Sorin Pop
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Two Phase Flow ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Thin Strip ◽  
Phase Flow ◽  
Two Phase ◽  
Averaged Model

scholarly journals Pore-Scale Modeling of the Effect of Wettability on Two-Phase Flow Properties for Newtonian and Non-Newtonian Fluids

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2832
Author(s):  
Moussa Tembely ◽  
Waleed S. Alameri ◽  
Ali M. AlSumaiti ◽  
Mohamed S. Jouini
Keyword(s):  
Contact Angle ◽  
Two Phase Flow ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Phase Flow ◽  
Pore Scale ◽  
Flow Properties ◽  
Two Phase ◽  
Oil Saturation

The Darcy-scale properties of reservoir rocks, such as capillary pressure and relative permeability, are controlled by multiphase flow properties at the pore scale. In the present paper, we implement a volume of fluid (VOF) method coupled with a physically based dynamic contact angle to perform pore-scale simulation of two-phase flow within a porous medium. The numerical model is based on the resolution of the Navier–Stokes equations as well as a phase fraction equation incorporating a dynamic contact angle model with wetting hysteresis effect. After the model is validated for a single phase, a two-phase flow simulation is performed on both a Newtonian and a non-Newtonian fluid; the latter consists of a polymer solution displaying a shear-thinning power law viscosity. To investigate the effects of contact angle hysteresis and the non-Newtonian nature of the fluid, simulations of both drainage and imbibition are carried out in order to analyze water and oil saturation—particularly critical parameters such as initial water saturation (Swi) and residual oil saturation (Sor) are assessed in terms of wettability. Additionally, the model sensitivities to the consistency factor (χ), the flow behavior index (n), and the advancing and receding contact angles are tested. Interestingly, the model correctly retrieves the variation in Sor and wettability and predicts behavior over a wide range of contact angles that are difficult to probe experimentally.

Wetting Effects on Two-Phase Flow in a Microchannel

2007 ◽  
Author(s):  
Alexandru Herescu ◽  
Jeffrey S. Allen
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Water Flow ◽  
High Speed ◽  
Two Phase Flow ◽  
Contact Angles ◽  
Phase Flow ◽  
Two Phase Flows ◽  
Two Phase ◽  
Number Systems

In the recent years there has been an increasing interest in the study of two-phase flows in low Bond number systems (where capillary forces are important relative to gravitational forces). Such systems include capillary tubes and microchannels as well as the gas flow channels of a PEM fuel cell. At the capillary scale, surface tension forces play an important role in two-phase flow regime transitions, pointing out the need to take into account the geometry of the cross section and the surface properties (wettability). Surface tension is generally considered in flow transitions, but the wetting properties of the fluid-surface material pairs (contact angle) are rarely given any importance. The researchers investigating two-phase flows should take extreme care when choosing the material of the test sections, as the flow morphology and the the pressure drop accordingly can vary widely with contact angle. In order to show these morphological changes high speed visualization experiments of air-water flow through 500 μm square and round microchannels were conducted. For the round channels, contact angles of less than 20° (wetting) and 105° (non-wetting) were investigated. For the square section, things are complicated by the presence of the corners. According to the Concus-Finn criterion, the liquid will wick into (wet) the corner if the contact angle is less then 45°, or will de-wet the corner if the contact angle is above 45°. A new case not previously mentioned in the literature arises for a contact angle of 45° ≤ θ ≤ 90°, for which the liquid is wetting the walls but dewetting the corners. Three contact angles of less than 20°, 80° and 105° are considered to investigate the possible morphologies in the square geometry. Images aquired with a high speed camera depicting the different flow morphologies that exist at the same air-water flow rates for each of the considered contact angle and geometry are presented.

Two-Dimensional Numerical Study of Two-Phase Flow (Gas-Liquid) in a Microchannel Mixer

2010 ◽  
Author(s):  
Tarek Abdel-Salam ◽  
Tuba Bayraktar ◽  
Srikanth Pidugu
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Two Phase Flow ◽  
Numerical Study ◽  
Space Station ◽  
Phase Flow ◽  
Microfluidic Systems ◽  
Two Phase ◽  
Velocity Surface ◽  
Bubble Length

Microfluidic systems are important in a variety of applications such as DNA sequencing, cell separation, environmental monitoring, heat transportation in spacecraft and space station [1–2]. Micromixers are the most important component in microfluidic systems and they can be classified as active and passive micromixers [3]. In micro dimensions, surface forces dominate over body forces requiring special attention for problems involving two-phase flows with free surfaces which are often driven by capillary forces [4]. In the present work the flow and mixing process in a passive microchannel mixer were numerically investigated. Effects of velocity, surface tension, and contact angle on the two phase flow were studied. Numerical results are obtained with a finite volume CFD code and using structured grids. Different liquids-gas Reynolds number ratios (Reliquid/Regas) were used ranging from 4 to 42. In addition, five values of the contact-angle (0 – 120) and seven values of the liquid surface tension (0.02 – 0.1) were used. Results show that increasing Reliquid increases the rate of the development of the air bubble. Increased surface tension resulted in increased bubble length. Bubble length decreased with increased contact angle till 75 degrees and further increase resulted in increased bubble length.

Numerical Investigation of Two-Phase Flow Over Unglazed Plate Collector Covered With Porous Material of Wire Screen for Solar Water Heater Application

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
T. Salameh ◽  
Y. Zurigat ◽  
A. Badran ◽  
C. Ghenai ◽  
M. El Haj Assad ◽  
...  
Keyword(s):  
Surface Tension ◽  
Porous Material ◽  
Water Flow ◽  
Two Phase Flow ◽  
Volume Fraction ◽  
Phase Flow ◽  
Two Phase ◽  
Solar Water ◽  
Wire Screen ◽  
Effect Of Surface

This paper presents three-dimensional numerical simulation results of the effect of surface tension on two-phase flow over unglazed collector covered with a wire screen. The homogenous model is used to simulate the flow with and without the effect of porous material of wire screen and surface tension. The Eulerian-Eulerian multiphase flow approach was used in this study. The phases are completely stratified, the interphase is well defined (free surface flow), and interphase transfer rate is very large. The liquid–solid interface, gas–liquid interface, and the volume fraction for both phases were considered as boundaries for this model. The results show that the use of porous material of wire screen will reduce the velocity of water flow and help the water flow to distribute evenly over unglazed plate collector. The possibility of forming any hot spot region on the surface was reduced. The water velocity with the effect of surface tension was found higher than the one without this effect, due to the extra momentum source added by surface tension in longitudinal direction. The use of porous material of wires assures an evenly distribution flow velocity over the inclined plate, therefore helps a net enhancement of heat transfer mechanism for unglazed solar water collector application.

Numerical Study of a Small Droplet Movement in a Microchannel under Heat Source

2019 ◽  
Vol 894 ◽  
pp. 104-111
Author(s):  
Thanh Long Le ◽  
Jyh Chen Chen ◽  
Huy Bich Nguyen
Keyword(s):  
Contact Angle ◽  
Heat Source ◽  
Water Droplet ◽  
Stokes Equations ◽  
Numerical Study ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Initial Position ◽  
Immiscible Fluids ◽  
Two Phase

In this study, the numerical computation is used to investigate the transient movement of a water droplet in a microchannel. For tracking the evolution of the free interface between two immiscible fluids, we employed the finite element method with the two-phase level set technique to solve the Navier-Stokes equations coupled with the energy equation. Both the upper wall and the bottom wall of the microchannel are set to be an ambient temperature. 40mW heat source is placed at the distance of 1 mm from the initial position of a water droplet. When the heat source is turned on, a pair of asymmetric thermocapillary convection vortices is formed inside the droplet and the thermocapillary on the receding side is smaller than that on the advancing side. The temperature gradient inside the droplet increases quickly at the initial times and then decreases versus time. Therefore, the actuation velocity of the water droplet first increases significantly, and then decreases continuously. The dynamic contact angle is strongly affected by the oil flow motion and the net thermocapillary momentum inside the droplet. The advancing contact angle is always larger than the receding contact angle during actuation process.

The Impact of Surface Tension on the Oil-Water Stratified Flow

2011 ◽  
Vol 383-390 ◽  
pp. 826-829 ◽  
Author(s):  
Dao Zhen Xu ◽  
Guo Zhong Zhang ◽  
Xin Zhang
Keyword(s):  
Surface Tension ◽  
Two Phase Flow ◽  
Large Diameter ◽  
Phase Flow ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Diameter Pipe ◽  
Small Density ◽  
Oil Water ◽  
The Impact

The stratified water-oil two—phase flow was modeled using VOF method in horizontal pipe and surface tension was taken into consideration using CSF model. It was found that the surface tension had great impact on the small density difference two-phase flow even in large diameter pipe, which would lead the interface curved and pressure gradient increased.

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