scholarly journals Study of Fluids Motion in a Microchannel under Heat Source

2020 ◽  
Vol 2 (SI2) ◽  
pp. First
Author(s):  
Long Thanh Le
Keyword(s):  
Contact Angle ◽  
Heat Source ◽  
Water Droplet ◽  
Stokes Equations ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Immiscible Fluids ◽  
Navier Stokes ◽  
Two Phase ◽  
Receding Contact Angle

In this study, the numerical computation is used to investigate the transient thermocapillary migration 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. The heat source is placed at the left side 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.

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.

scholarly journals Numerical investigation of the thermocapillary migration of a water droplet in a microchannel by applying a heat source

2020 ◽  
Vol 3 (SI1) ◽  
pp. First
Author(s):  
Le Thanh Long ◽  
Jyh Chen Chen ◽  
Nguyen Huy Bich
Keyword(s):  
Contact Angle ◽  
Heat Source ◽  
Water Droplet ◽  
Stokes Equations ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Initial Position ◽  
Immiscible Fluids ◽  
Two Phase ◽  
Thermocapillary Migration

The migration of a small droplet has been developed during the last two decades due to its applications in industry and high technology such as MEMS and NEMS devices, Lap-On-a- chip, transportation of fluids and so on. There have many studies on this topic in which the energy source as a driving force for the moving of a droplet is quite a difference like heating, magnetics, pressure, electric, laser, and so on. In this study, the numerical computation is used to investigate the transient thermocapillary migration of a water droplet in a micro-channel under the effect of heating source. 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 and continuity equation coupled with the energy equation. Both the upper wall and the bottom wall of the microchannel are set to be ambient temperature. 40mW heat source is placed at a 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. Furthermore, the results also indicate that 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 the actuation process.

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.

scholarly journals A simulation study of the forward and backward thermocapillary migration of fluids in a microchannel

2020 ◽  
Vol 3 (4) ◽  
pp. first
Author(s):  
Long Thanh Le ◽  
Khuong Huu Nguyen
Keyword(s):  
Heat Source ◽  
Water Droplet ◽  
Thermocapillary Convection ◽  
Liquid Droplet ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Immiscible Fluids ◽  
Cold Side ◽  
Free Interface ◽  
Thermocapillary Migration

In this study, the forward and backward thermocapillary migration of fluids in a microchannel is numerically investigated. Both the upper wall and the lower wall of the microchannel are set to be an ambient temperature. Two 40mW heat sources activated periodically are placed on the left side and the right side of the droplet in a microchannel. When the heat source is turned on, a pair of asymmetric thermocapillary convection vortices is formed inside the droplet. The isotherms inside the droplet are extremely distorted by the thermocapillary convection. The forward and backward thermocapillary migration results in the net thermocapillary momentum which drives a water droplet moves from the hot side of the open channel to the cold side. The temperature gradient at the free interface on the side of acting heat source is always smaller than that on the cold side. The actuation velocity of the liquid droplet first increases significantly, and then decreases continuously for various interval times. The dynamic contact angle of a water droplet is strongly affected by the forward and backward oil flow motion and the net thermocapillary momentum inside the droplet. It is alternated due to the pressure difference acting on the free interface between two immiscible fluids during actuation process.

scholarly journals A ternary Cahn–Hilliard–Navier–Stokes model for two-phase flow with precipitation and dissolution

2020 ◽  
pp. 1-35
Author(s):  
Christian Rohde ◽  
Lars von Wolff
Keyword(s):  
Phase Field ◽  
Stokes Equations ◽  
Solid Phase ◽  
Immiscible Fluids ◽  
Sharp Interface ◽  
Ion Concentration ◽  
Navier Stokes ◽  
Interface Model ◽  
Sharp Interface Model ◽  
Two Phase

We consider the incompressible flow of two immiscible fluids in the presence of a solid phase that undergoes changes in time due to precipitation and dissolution effects. Based on a seminal sharp interface model a phase-field approach is suggested that couples the Navier–Stokes equations and the solid’s ion concentration transport equation with the Cahn–Hilliard evolution for the phase fields. The model is shown to preserve the fundamental conservation constraints and to obey the second law of thermodynamics for a novel free energy formulation. An extended analysis for vanishing interfacial width reveals that in this limit the sharp interface model is recovered, including all relevant transmission conditions. Notably, the new phase-field model is able to realize Navier-slip conditions for solid–fluid interfaces in the limit.

A novel model for oil-water stratified flow in horizontal wells with a curved interface based on dynamic contact angle

2021 ◽  
pp. 1-14
Author(s):  
Songyi Guo ◽  
Zhiming Wang ◽  
Quanshu Zeng
Keyword(s):  
Contact Angle ◽  
Dynamic Contact Angle ◽  
Water Layer ◽  
Dynamic Contact ◽  
The Novel ◽  
Two Phase ◽  
Flow Area ◽  
Well Completion ◽  
Oil Water ◽  
Novel Model

Abstract During the process of oil production and transportation, oil-water two-phase flow is a common occurrence. Well completion optimization and production design are greatly affected by the prediction accuracy of two-phase flow characteristics. In this paper, a novel model was proposed to predict the influence of interface shape on stratified flow. Dynamic contact angle theory and minimum energy method were introduced to solve the momentum equations with a curved interface and dispersed phase holdup in the lower water layer or the upper oil layer, respectively. If the interface shape changes from a flat surface to a curved surface, the flow area of the upper water layer will increase, and the flow area of the lower oil layer will decrease. Results showed that the dynamic contact angle and pressure gradient are greatly affected by oil superficial velocity, oil viscosity, and pipe diameter. By comparing the prediction with available experiment results, the validity of the model was evaluated. Results showed that the novel model had an overall good prediction performance for the dimensionless height of the oil-water interface at the mid-plane, the dimensionless height of water climbing, and the pressure gradient, with an average percentage error of 8.32%,16.09%, and 13.12%, respectively. The novel model is a unified model that could be used to solve the problem with a curved/flat interface. It will also promote the oil well production design and horizontal well completion optimization.

ANALYSIS OF A PHASE-FIELD MODEL FOR TWO-PHASE COMPRESSIBLE FLUIDS

2010 ◽  
Vol 20 (07) ◽  
pp. 1129-1160 ◽  
Author(s):  
EDUARD FEIREISL ◽  
HANA PETZELTOVÁ ◽  
ELISABETTA ROCCA ◽  
GIULIO SCHIMPERNA
Keyword(s):  
Field Model ◽  
Stokes Equations ◽  
Phase Field Model ◽  
Immiscible Fluids ◽  
Compressible Fluids ◽  
Navier Stokes ◽  
Two Phase ◽  
Navier Stokes Equations ◽  
Cahn Equation ◽  
System Coupling

A model describing the evolution of a binary mixture of compressible, viscous, and macroscopically immiscible fluids is investigated. The existence of global-in-time weak solutions for the resulting system coupling the compressible Navier–Stokes equations governing the motion of the mixture with the Allen–Cahn equation for the order parameter is proved without any restriction on the size of initial data.

Sign in / Sign up

Export Citation Format

Share Document