Lattice Boltzmann Simulation of Droplet Formation in Non-Newtonian Fluids

2015 ◽  
Vol 17 (4) ◽  
pp. 1056-1072 ◽  
Author(s):  
Y. Shi ◽  
G. H. Tang
Keyword(s):  
Newtonian Fluid ◽  
Power Law ◽  
Lattice Boltzmann ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Droplet Generation ◽  
Bgk Model ◽  
Lattice Boltzmann Simulation ◽  
Power Law Exponent ◽  
Boltzmann Method

AbstractNewtonian and non-Newtonian dispersed phase droplet formation in non-Newtonian continuous phase in T-junction and cross junction microchannels are investigated by the immiscible lattice BGK model. The effects of the non-Newtonian fluid power-law exponent, viscosity and interfacial tension on the generation of the droplet are studied. The final droplet size, droplet generation frequency, and detachment point of the droplet change with the power-law exponent. The results reveal that it is necessary to take into account the non-Newtonian rheology instead of simple Newtonian fluid assumption in numerical simulations. The present analysis also demonstrates that the lattice Boltzmann method is of potential to investigate the non-Newtonian droplet generation in multiphase flow.

LATTICE BOLTZMANN SIMULATION OF A SINGLE CHARGED ELLIPTIC CYLINDER IN A NEWTONIAN FLUID

2004 ◽  
Vol 18 (17n19) ◽  
pp. 2757-2761 ◽  
Author(s):  
CAOYING ZHANG ◽  
HUILI TAN ◽  
MUREN LIU ◽  
LINGJIANG KONG ◽  
HAIPING FANG
Keyword(s):  
Newtonian Fluid ◽  
Lattice Boltzmann ◽  
Present Model ◽  
Elliptic Cylinder ◽  
Coulomb Force ◽  
Initial Condition ◽  
Two Dimensional ◽  
Dynamics Model ◽  
Lattice Boltzmann Simulation ◽  
Boltzmann Method

A two-dimensional dynamics model of an elliptic cylinder is derived by using the lattice Boltzmann method. With the present model, we have simulated the sedimentation of a single charged elliptic cylinder in a two-dimensional tube in a Newtonian fluid. Due to the polarizing effects and non-axial symmetry shape, there are the Coulomb force and the Coulomb torque on the elliptic cylinder during the sedimentation, which change its ordinary motion significantly. Comparing with the sedimentation of an un-charged elliptic cylinder under the same initial condition, we have further discussed the dynamics characteristics of the charged elliptic cylinder, and obtained some interesting results.

Lattice Boltzmann Simulation of Non-Newtonian Flow Past Cylinders

2010 ◽  
Author(s):  
Amir Nejat ◽  
Koohyar Vahidkhah ◽  
Vahid Abdollahi
Keyword(s):  
Power Law ◽  
Lattice Boltzmann ◽  
Flow Simulation ◽  
Distribution Functions ◽  
Newtonian Flow ◽  
Lattice Distribution ◽  
Flow Past ◽  
Lattice Boltzmann Simulation ◽  
Boltzmann Method ◽  
Power Law Index

A second-order lattice Boltzmann algorithm is used for power-law non-Newtonian flow simulation. The shear dependent behavior of the fluid is implemented through calculating the shear locally from the lattice distribution functions. The flow past a series of tandem arrangement of two cylinders is computed in a confined domain. The effect of Reynolds number and the power-law index on drag coefficients of the cylinders are examined in detail. The present study clearly reveals the capability of the lattice Boltzmann method in successful simulation of the complicated non-Newtonian flow fields.

scholarly journals Droplet Formation in a T-Junction Microfluidic Device in the Presence of an Electric Field

2015 ◽  
Author(s):  
Zeeshan Ahmad ◽  
Rattandeep Singh ◽  
Supreet Singh Bahga ◽  
Amit Gupta
Keyword(s):  
Electric Field ◽  
Microfluidic Device ◽  
Lattice Boltzmann ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Immiscible Fluids ◽  
Multiphase Model ◽  
Dispersed Phases ◽  
Rate Ratios ◽  
Boltzmann Method

In this work, the effect of applying an electric field on droplet formation in a T-junction microfluidic device is examined by simulations based on a recent technique known as lattice Boltzmann method (LBM). The electric field is applied in the main channel just beyond the confluence of the continuous and dispersed phases. A combined electrohydrodynamics-multiphase model that can simulate the flow of immiscible fluids in the presence of an electric field is developed and validated. The same model is then applied to study the droplet formation process in a T-junction microfluidic device at a capillary number of 0.01 and at different dispersed to continuous phase flow rate ratios. Results show that there is a decrease in the droplet size and an increase in formation frequency as the electric field is increased. The interplay of the electric and interfacial forces on droplet formation is investigated.

Effect of Geometry on Droplet Generation in a Microfluidic T-Junction

2013 ◽  
Author(s):  
Katerina Loizou ◽  
Wim Thielemans ◽  
Buddhika N. Hewakandamby
Keyword(s):  
Aspect Ratio ◽  
Cross Section ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Main Channel ◽  
Superficial Velocity ◽  
Droplet Generation ◽  
Dispersed Phase ◽  
Aspect Ratios ◽  
The Cross

The main aim of this study is to examine how the droplet formation in microfluidic T-junctions is influenced by the cross-section and aspect ratio of the microchannels. Several studies focusing on droplet formation in microfluidic devices have investigated the effect of geometry on droplet generation in terms of the ratio between the width of the main channel and the width of the side arm of the T-junction. However, the contribution of the aspect ratio and thus that of the cross-section on the mechanism of break up has not been examined thoroughly with most of the existing work performed in the squeezing regime. Two different microchannel geometries of varying aspect ratios are employed in an attempt to quantify the effect of the ratio between the width of the main channel and the height of the channel on droplet formation. As both height and width of microchannels affect the area on which shear stress acts deforming the dispersed phase fluid thread up to the limit of detaching a droplet, it is postulated that geometry and specifically cross-section of the main channel contribute on the droplet break-up mechanisms and should not be neglected. The above hypothesis is examined in detail, comparing the volume of generated microdroplets at constant flowrate ratios and superficial velocities of continuous phase in two microchannel systems of two different aspect ratios operating at dripping regime. High-speed imaging has been utilised to visualise and measure droplets formed at different flowrates corresponding to constant superficial velocities. Comparing volumes of generated droplets in the two geometries of area ratio near 1.5, a significant increase in volume is reported for the larger aspect ratio utilised, at all superficial velocities tested. As both superficial velocity of continuous phase and flowrate ratio are fixed, superficial velocity of dispersed phase varies. However this variation is not considered to be large enough to justify the significant increase in the droplet volume. Therefore it can be concluded that droplet generation is influenced by the aspect ratio and thus the cross-section of the main channel and its effect should not be depreciated. The paper will present supporting evidence in detail and a comparison of the findings with the existing theories which are mainly focused on the squeezing regime.

scholarly journals A Multiple-Grid Lattice Boltzmann Method for Natural Convection under Low and High Prandtl Numbers

Fluids ◽  
2021 ◽  
Vol 6 (4) ◽  
pp. 148
Author(s):  
Seyed Amin Nabavizadeh ◽  
Himel Barua ◽  
Mohsen Eshraghi ◽  
Sergio D. Felicelli
Keyword(s):  
Natural Convection ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Large Scale ◽  
Bgk Model ◽  
Flow Equations ◽  
Wide Range ◽  
Prandtl Numbers ◽  
Boltzmann Method ◽  
Benchmark Solutions

A multi-distribution lattice Boltzmann Bhatnagar–Gross–Krook (BGK) model with a multiple-grid lattice Boltzmann (MGLB) model is proposed to efficiently simulate natural convection over a wide range of Prandtl numbers. In this method, different grid sizes and time steps for heat transfer and fluid flow equations are chosen. The model is validated against natural convection in a square cavity, since extensive benchmark solutions are available for that problem. The proposed method can resolve the computational difficulty in simulating problems with very different time scales, in particular, when using extremely low or high Prandtl numbers. The technique can also enhance computational speed and stability while keeping the simplicity of the BGK method. Compared with the conventional lattice Boltzmann method, the simulation time can be reduced up to one-tenth of the time while maintaining the accuracy in an acceptable range. The proposed model can be extended to other lattice Boltzmann collision models and three-dimensional cases, making it a great candidate for large-scale simulations.

scholarly journals Lattice Boltzmann Simulation of Natural Convection in an Annulus between a Hexagonal Cylinder and a Square Enclosure

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
L. El Moutaouakil ◽  
Z. Zrikem ◽  
A. Abdelbaki
Keyword(s):  
Natural Convection ◽  
Rayleigh Number ◽  
Cross Section ◽  
Lattice Boltzmann ◽  
Square Enclosure ◽  
Lattice Boltzmann Simulation ◽  
Laminar Natural Convection ◽  
Heat Transfers ◽  
Boltzmann Method ◽  
Vertical Case

Laminar natural convection in a water filled square enclosure containing at its center a horizontal hexagonal cylinder is studied by the lattice Boltzmann method. The hexagonal cylinder is heated while the walls of the cavity are maintained at the same cold temperature. Two orientations are treated, corresponding to two opposite sides of the hexagonal cross-section which are horizontal (case I) or vertical (case II). For each case, the results are presented in terms of streamlines, isotherms, local and average convective heat transfers as a function of the dimensionless size of the hexagonal cylinder cross-section (0.1≤B≤0.4), and the Rayleigh number (103≤Ra≤106).

scholarly journals Lattice Boltzmann simulation of two-sided lid-driven flow in deep cavities

2015 ◽  
pp. 157-168
Author(s):  
Natasa Lukic ◽  
Predrag Tekic ◽  
Jelena Radjenovic ◽  
Ivana Sijacki
Keyword(s):  
Aspect Ratio ◽  
Flow Pattern ◽  
Lattice Boltzmann ◽  
Reynolds Numbers ◽  
Critical Aspect ◽  
Symmetric Flow ◽  
Primary Vortex ◽  
Lattice Boltzmann Simulation ◽  
Boltzmann Method ◽  
Deep Cavities

The present study is concerned with two-sided lid-driven incompressible flow in rectangular, deep cavities applying lattice Boltzmann method. After validating the code for the square cavity, solutions for cavities with an aspect ratio 1.5 and 4 were obtained for the Reynolds numbers of 100, 400, 1000 and 3200. The influence of the Reynolds number and aspect ratio on the flow pattern and on the characteristics of vortices inside the cavity was studied. Symmetric flow pattern was obtained for all investigated cases. The middle of the cavity is mostly influenced by the increase in the aspect ratio. Critical aspect ratio, at which the birth of a primary vortex in the middle of the cavity takes place, was determined to be between 2.7 and 2.725.

scholarly journals Lattice Boltzmann simulation of liquid falling on horizontal rectangular pillar arrays

2021 ◽  
Vol 321 ◽  
pp. 01014
Author(s):  
Makoto Sugimoto ◽  
Tatsuya Miyazaki ◽  
Zelin Li ◽  
Masayuki Kaneda ◽  
Kazuhiko Suga
Keyword(s):  
Lattice Boltzmann ◽  
Three Dimensional ◽  
Phase Field Model ◽  
Flow Simulation ◽  
High Viscosity ◽  
Two Phase ◽  
Lattice Boltzmann Simulation ◽  
Pillar Arrays ◽  
Boltzmann Method ◽  
Behavior Characteristic

Stator coils of automobiles in operation generate heat and are cooled by a coolant poured from above. Since the behavior characteristic of the coolant poured on the coils is not clarified yet due to its complexity, the three-dimensional two-phase flow simulation is conducted. In this study, as a steppingstone to the simulation of the liquid falling on the actual coils, the coils are modelled with horizontal rectangular pillar arrays whose governing parameters can be easily changed. The two-phase flows are simulated using the lattice Boltzmann method and the phase-field model, and the effects of the governing parameters, such as the physical properties of the cooling liquid, the wettability, and the gap between the pillars, on the wetting area are investigated. The results show that the oil tends to spread across the pillars because of its high viscosity. Moreover, the liquid spreads quickly when the contact angle is small. In the case that the pillars are stacked, the wetting area of the inner pillars is larger than that of the exposed pillars.

Modeling of collapsing cavitation bubble near solid wall by 3D pseudopotential multi-relaxation-time lattice Boltzmann method

2017 ◽  
Vol 232 (3) ◽  
pp. 445-456 ◽  
Author(s):  
Minglei Shan ◽  
Yu Yang ◽  
Hao Peng ◽  
Qingbang Han ◽  
Changping Zhu
Keyword(s):  
Relaxation Time ◽  
Lattice Boltzmann ◽  
Cavitation Bubble ◽  
Solid Wall ◽  
Three Dimensional ◽  
Lattice Boltzmann Model ◽  
Bubble Collapse ◽  
Lattice Boltzmann Simulation ◽  
Boltzmann Method ◽  
Boltzmann Model

Understanding the dynamic characteristic of the cavitation bubble near a solid wall is a fundamental issue for the bubble collapse application and prevention. In the present work, an improved three-dimensional multi-relaxation-time pseudopotential lattice Boltzmann model is adopted to investigate the cavitation bubble collapse near the solid wall. With respect to thermodynamic consistency, Laplace law verification, the three-dimensional pseudopotential multi-relaxation-time lattice Boltzmann model is investigated. By the theoretical analysis, it is proved that the model can be regarded as a solver of the Rayleigh–Plesset equation, and confirmed by comparing the results of the lattice Boltzmann simulation and the Rayleigh–Plesset equation calculation for the case of cavitation bubble collapse in the infinite medium field. The bubble collapse near the solid wall is modeled using the improved pseudopotential multi-relaxation-time lattice Boltzmann model. We find the lattice Boltzmann simulation and the experimental results have the same dynamic process by comparing the bubble profiles evolution. Form the pressure field and the velocity field evolution it is found that the tapered higher pressure region formed near the top of the bubble is a crucial driving force inducing the bubble collapse. This exploratory research demonstrates that the lattice Boltzmann method is an alternative tool for the study of the interaction between collapsing cavitation bubble and matter.

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