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    Applicability of lattice Boltzmann method in simulation of drops and bubbles formation and transport

    , Article AIP Conference Proceedings, 22 September 2014 through 28 September 2014 ; Volume 1648 , 2015 ; 0094243X (ISSN) ; 9780735412873 (ISBN) Taeibi Rahni, M ; Alizadeh, M ; Haghshenas, M ; Salimi, H ; Najafi, M ; Miller, R ; Sharif University of Technology
    Abstract
    Multiphase flows appear in many scientific and engineering applications. On the other hand, there has been a tremendous experimental and numerical investigation trying to understand complex fluid-fluid interfaces better. However, conventional CFD have certain limitations in complicated situations. Fortunately in the past two decades, new approaches, namely SPH and LBM (sometimes called meshless methods) have been developed. Since they are mesoscopic, they have been able to perform much better than conventional CFD. Especially, LBM is becoming more and more popular and has already been divided to many branches  

    Implementation of a high-order compact finite-difference lattice Boltzmann method in generalized curvilinear coordinates

    , Article Journal of Computational Physics ; Vol. 267 , 2014 , Pages 28-49 ; ISSN: 00219991 Hejranfar, K ; Ezzatneshan, E ; Sharif University of Technology
    Abstract
    In this work, the implementation of a high-order compact finite-difference lattice Boltzmann method (CFDLBM) is performed in the generalized curvilinear coordinates to improve the computational efficiency of the solution algorithm to handle curved geometries with non-uniform grids. The incompressible form of the discrete Boltzmann equation with the Bhatnagar-Gross-Krook (BGK) approximation with the pressure as the independent dynamic variable is transformed into the generalized curvilinear coordinates. Herein, the spatial derivatives in the resulting lattice Boltzmann (LB) equation in the computational plane are discretized by using the fourth-order compact finite-difference scheme and the... 

    A new approach to reduce memory consumption in lattice boltzmann method on GPU

    , Article Journal of Applied Fluid Mechanics ; Volume 10, Issue 1 , 2017 , Pages 55-67 ; 17353572 (ISSN) Sheida, M ; Taeibi Rahni, M ; Esfahanian, V ; Sharif University of Technology
    Isfahan University of Technology  2017
    Abstract
    Several efforts have been performed to improve LBM defects related to its computational performance. In this work, a new algorithm has been introduced to reduce memory consumption. In the past, most LBM developers have not paid enough attention to retain LBM simplicity in their modified version, while it has been one of the main concerns in developing of the present algorithm. Note, there is also a deficiency in our new algorithm. Besides the memory reduction, because of high memory call back from the main memory, some computational efficiency reduction occurs. To overcome this difficulty, an optimization approach has been introduced, which has recovered this efficiency to the original... 

    Numerical Investigation of Nano-Particles Dispersion and Deposition in Crossing of Elliptical Obstacles Networkusing Lattice Boltzmann Method

    , M.Sc. Thesis Sharif University of Technology Piri, Salman (Author) ; Moosavi, Ali (Supervisor)
    Abstract
    Investigation of transport and deposition of aerosol particles has been of interest to researchers in many branches of science. Various numerical and experimental methods has been utilized in particulate fluid flows studies. In recent relevant researches lattice Boltzmann method has been widely used and is reported to be a robust and efficient method. In present study, numerical investigation of dispersion and deposition of aerosol particles is studies in the channel, containing elliptical obstacles geometry using Lattice Boltzmann Method. Fluid flow simulations are performed using LBM while for the study of particle transport and deposition, tracking and the motion equations of them,... 

    Investigation of flow around a confined elliptical cylinder using the Lattice Boltzmann method

    , Article Middle East Journal of Scientific Research ; Volume 15, Issue 1 , 2013 , Pages 8-13 ; 19909233 (ISSN) Taeibi Rahni, M ; Esfahanian, V ; Salari, M ; Sharif University of Technology
    2013
    Abstract
    This paper deals with the investigation of the laminar flow past an elliptical cylinder confined in a channel. In this paper, the Lattice Boltzmann (LB) method is used to simulate flow in two dimensions. The present LB method with the used boundary conditions is validated in simulations of the incompressible flow past a circular cylinder. The simulations are carried out in a range of condition, 0≤θ≤90 (angle of incidence), 5≤Re≤100, (Reynolds number) for AR=0.25,0.5 (aspect ratio). The effects of those parameters on the drag and lift coefficients and other flow characteristics of the cylinder are examined in detail. The results demonstrate that the drag and lift coefficients increase with... 

    Investigation of flow around a confined elliptical cylinder using the Lattice Boltzmann method

    , Article World Applied Sciences Journal ; Volume 22, Issue 7 , 2013 , Pages 1013-1018 ; 18184952 (ISSN) Taeibi Rahni, M ; Salari, M ; Esfahanian, V ; Sharif University of Technology
    2013
    Abstract
    This paper deals with the investigation of the laminar flow past an elliptical cylinder confined in a channel. In this paper, the Lattice Boltzmann (LB) method is used to simulate flow in two dimensions. The present LB method with the used boundary conditions is validated in simulations of the incompressible flow past a circular cylinder. The simulations are carried out in a range of condition, 0 90 (angle of incidence), 5 Re 100, (Reynolds number) for AR=0.25,0.5 (aspect ratio). The effects of those parameters on the drag and lift coefficients and other flow characteristics of the cylinder are examined in detail. The results demonstrate that the drag and lift coefficients increase with the... 

    The dynamics of wettability driven droplets in smooth and corrugated microchannels

    , Article Journal of Statistical Mechanics: Theory and Experiment ; Volume 2012, Issue 10 , 2012 ; 17425468 (ISSN) Esmaili, E ; Moosavi, A ; Mazloomi, A ; Sharif University of Technology
    IOP  2012
    Abstract
    A multi-component lattice Boltzmann scheme is used to investigate the dynamics of a wettability driven droplet within a microchannel. The driving force for the motion is created by a stepwise change in the wettability of the channel walls. Moreover, an analytical solution is developed for evaluation of the dynamics of the droplet inside the channel. The effects of various parameters such as the height of the channel, the wetting pattern of the channel walls, the viscosity and the density ratio on the dynamics are studied. Also, the effect of grooves of different sizes on the channel surfaces on the dynamics of the droplet is investigated for both hydrophilic and hydrophobic surfaces.... 

    Permeability correlation with porosity and Knudsen number for rarefied gas flow in Sierpinski carpets

    , Article Journal of Natural Gas Science and Engineering ; Volume 56 , 2018 , Pages 549-567 ; 18755100 (ISSN) Rostamzadeh, H ; Salimi, M. R ; Taeibi Rahni, M ; Sharif University of Technology
    Elsevier B.V  2018
    Abstract
    In recent years, application of porous media is highlighted among researchers due to their wide range of usability in micro-scale problems, such as gas reservoirs, micro-filtering, heat exchangers, etc. With this respect, the accurate description of flow behavior using governing equations based on the continuum assumption is not valid since the mean free path is comparable to the characteristics length of the problem. For this purpose, a simple methodology for diffusion reflection boundary condition is developed and validated for two valuable benchmarks, namely micro-channel flow and fractal porous media, where the results were in good agreement with literature. Then, pore-scale simulation... 

    Drop formation in cross-junction micro-channel using lattice Boltzmann method

    , Article Thermal Science ; Volume 22, Issue 2 , 2018 , Pages 909-919 ; 03549836 (ISSN) Fallah, K ; Taeibi Rahni, M ; Mohammadzadeh, A ; Najafi, M ; Sharif University of Technology
    Serbian Society of Heat Transfer Engineers  2018
    Abstract
    Drop formation in cross-junction micro-channels is numerically studied using the lattice Boltzmann method with pseudo-potential model. To verify the simulation, the results are compared to previous numerical and experimental data. Furthermore, the effects of capillary number, flow rate ratio, contact angle, and viscosity ratio on the flow patterns, drop length, and interval between drops are investigated and highlighted. The results show that the drop forming process has different regimes, namely, jetting, drop, and squeezing regimes. Also, it is shown that increasing in the flow rate ratio in the squeezing regime causes increment in drop length and decrement in drops interval distance. On... 

    Numerical study on free convection in a U-shaped CuO/water nanofluid-filled cavity with different aspect ratios using double-MRT lattice Boltzmann

    , Article Thermal Science and Engineering Progress ; Volume 14 , 2019 ; 24519049 (ISSN) Hasanzadeh Fard, A ; Hooshmand, P ; Mohammaei, M ; Ross, D ; Sharif University of Technology
    Elsevier Ltd  2019
    Abstract
    The lattice Boltzmann simulation of natural convection fluid flow and heat transfer is performed. The double-MRT lattice Boltzmann method is employed. The D2Q5 and D2Q9 lattice models are used to simulate the temperature field and flow field, respectively. The configuration of the cavity is U-shaped, and the cavity is filled with CuO-water nanofluid. The KKL (Koo-Kleinstreuer-Li) model is utilized to estimate the thermal conductivity and dynamic viscosity; as well as, the nanoparticle shape effect on the thermo-physical properties of nanofluid is considered. The streamlines, temperature distribution, local entropy generation map, average Nusselt number, magnitude of total entropy generation... 

    Flow control in a cavity with tiny-obstacles on the walls for mixing enhancement part I: Flow physics

    , Article Journal of Applied Fluid Mechanics ; Volume 12, Issue 1 , 2019 , Pages 11-23 ; 17353572 (ISSN) Maneshian, B ; Javadi, K ; Taeibi Rahni, M ; Sharif University of Technology
    Isfahan University of Technology  2019
    Abstract
    This paper seeks to make a study on flow control in two-dimensional square cavities having obstacles on their walls. The goal of using these passive controllers is to enhance mixing in an enclosed space. Lattice Boltzmann method is used to simulate the problem. Results are presented for various Reynolds numbers, 400≤Re≤4000 and different arrangements of tiny-obstacles with different heights. To give a perspective on the physics of this problem, time evolution of the flow is studied at Re= 1000. Then, the flow structure is studied for different Reynolds numbers. Findings show that the interaction of the main vortex with the tiny-obstacles inserted on the wall cavity changes the flow pattern... 

    Flow control in a cavity with tiny-obstacles on the walls for mixing enhancement part I: Flow physics

    , Article Journal of Applied Fluid Mechanics ; Volume 12, Issue 1 , 2019 , Pages 11-23 ; 17353572 (ISSN) Maneshian, B ; Javadi, K ; Taeibi Rahni, M ; Sharif University of Technology
    Isfahan University of Technology  2019
    Abstract
    This paper seeks to make a study on flow control in two-dimensional square cavities having obstacles on their walls. The goal of using these passive controllers is to enhance mixing in an enclosed space. Lattice Boltzmann method is used to simulate the problem. Results are presented for various Reynolds numbers, 400≤Re≤4000 and different arrangements of tiny-obstacles with different heights. To give a perspective on the physics of this problem, time evolution of the flow is studied at Re= 1000. Then, the flow structure is studied for different Reynolds numbers. Findings show that the interaction of the main vortex with the tiny-obstacles inserted on the wall cavity changes the flow pattern... 

    Innovations in non-linear oscillations of a pendent drop from a capillary tip during formation and detachment - an LBM simulation

    , Article Journal of Applied Fluid Mechanics ; Volume 14, Issue 1 , 2020 , Pages 331-344 Ghorbanifar, S ; Taeibi Rahni, M ; Zareh, M ; Sharif University of Technology
    Isfahan University of Technology  2020
    Abstract
    Individual drops are suitable tools to study the liquid-fluid interfacial properties. In this work, force-displacement equation and non-linear oscillations of a pendent drop are numerically investigated. The presented novel force-displacement function allows following the dynamics of a pendent drop and realizing its elastic behavior. The growth and detachment of drop, which is pending due to gravity from a capillary tip, is considered (assuming high density and high viscosity ratios and immiscible two-phase flows). Two-dimensional multi-relaxation time lattice Boltzmann method (MRT-LBM) was used to simulate growth, detachment, and oscillations of the drop using a conservative model for... 

    Implementing Appropriate Numerical Filters in the Lattice Boltzmann Method for Solving Multiphase Incompressible Flows with Large Density Ratio

    , M.Sc. Thesis Sharif University of Technology Bidi, Saeed (Author) ; Hejranfar, Kazem (Supervisor)
    Abstract
    In this study, two finite-difference lattice Boltzmann methods (FDLBM) are applied and assessed for the simulation of two-phase liquid-vapor flows with high density ratios. For this aim, the He-Shan-Doolen type lattice Boltzmann multiphase model is used and the spatial derivatives in the resulting system of equations are discretized by using the second-order central difference and modified Lax-Wendroff schemes. Suitable numerical dissipation terms and filters are applied to regularize the numerical solution and remove spurious waves generated by flow nonlinearities in smooth regions and at the same time to remove the numerical oscillations in the interface region of the two phases.Three... 

    3D investigation of natural convection of nanofluids in a curved boundary enclosure applying lattice Boltzmann method

    , Article International Journal of Numerical Methods for Heat and Fluid Flow ; Volume 28, Issue 8 , 2018 , Pages 1827-1844 ; 09615539 (ISSN) Hosseini Abadshapoori, M ; Saidi, M. H ; Sharif University of Technology
    Emerald Group Publishing Ltd  2018
    Abstract
    Purpose: The purpose of this paper is to investigate the natural convection behavior of nanofluids in an enclosure. The enclosure is a 3D capsule with curved boundaries filled with TiO2-water nanofluid. Design/methodology/approach: In this paper, a multiple relaxation times lattice Boltzmann method (MRT-LBM) has been used. Two-component LBM has been conducted to consider the interaction forces between nanoparticles and the base fluid. Findings: Results show that the enhanced Nusselt number (Nu*) increases with the increase in volume fraction of nanoparticles (ϕ) and Ra number and decrease of nanoparticle size (λ). Additionally, the findings indicate that increasing volume fraction beyond a... 

    Pore-scale modeling of rarefied gas flow in fractal micro-porous media, using lattice Boltzmann method (LBM)

    , Article Journal of Thermal Analysis and Calorimetry ; Volume 135, Issue 3 , 2019 , Pages 1931-1942 ; 13886150 (ISSN) Rostamzadeh, H ; Salimi, M. R ; Taeibi Rahni, M ; Sharif University of Technology
    Springer Netherlands  2019
    Abstract
    Due to the widespread use of rarefied gas flow in micro-porous media in industrial and engineering problems, a pore-scale modeling of rarefied gas flow through two micro-porous media with fractal geometries is presented, using lattice Boltzmann method. For this purpose, square- and circular-based Sierpinski carpets with fractal geometries are selected due to their inherent behavior for real porous media. Diffusive reflection slip model is used and developed for these porous media through this study. With this respect, the planar Poiseuille flow is selected as a benchmark and validated with the literature. The effect of Knudsen number (Kn) on the permeability is investigated and compared in... 

    Development of Chebyshev Collocation Spectral Lattice Boltzmann Method for Solution of LowSpeed Flows

    , M.Sc. Thesis Sharif University of Technology Haji Hassan Pour, Mahya (Author) ; Hejranfar, Kazem (Supervisor)
    Abstract
    In this study, a Chebyshev collocation spectral lattice Boltzmann method (CCSLBM) is developed and assessed for the computation of low speed flows. Both steady and unsteady flows are considered here. The discrete Boltzmann equation (DBE) with the Bhatnagar-Gross-Krook (BGK) approximation based on the pressure distribution function is considered and the space discretization is performed by the Chebyshev collocation spectral method to achieve a highly accurate flow solver. To provide accurate unsteady solutions, the time integration of the temporal term in the LB equation is made by the fourth-order Runge-Kuta scheme. To achieve numerical stability and accuracy, the physical boundary... 

    Simulating Flow over Nanoparticles through Microchannels Using Lattice Boltzmann Method

    , M.Sc. Thesis Sharif University of Technology Setayeshgar, Alireza (Author) ; Darbandi, Masoud (Supervisor)
    Abstract
    Novel manufacturing technologies in micro scales, such as micro machining, guide us through constructing micro scale systems known as MEMS. These systems have a wide range of applications, from fabrication of electrostatic, magnetic, pneumatic sensors and actuators to micro mechanical gears and motors. Also, MEMS applications involve the manipulation of one or more fluids, known as microfluids. Simulation of flow through microchannels over nano particles has important applications in solid particles transport. In this flow, the rarefaction phenomenon will affect the flow behavior and its subsequent impacts such as aerodynamic drag forces. In this work, we use the Lattice Boltzmann method... 

    Numerical simulation of drag reduction in microgrooved substrates using lattice-boltzmann method

    , Article Journal of Fluids Engineering, Transactions of the ASME ; Volume 141, Issue 7 , 2019 ; 00982202 (ISSN) Asadzadeh, H ; Moosavi, A ; Etemadi, A ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2019
    Abstract
    We study drag reduction of a uniform flow over a flat surface due to a series of rectangular microgrooves created on the surface. The results reveal that making grooves on the surface usually leads to the generation of secondary vortices inside the grooves that, in turn, decreases the friction drag force and increases the pressure drag force. By increasing the thickness of the grooves to the thickness of the obstacle, the pressure drag increases due to the enhancement of the generated vortices and the occurrence of separation phenomenon and the friction drag reduces due to a decrease of the velocity gradient on the surface. In addition, by increasing the grooves depth ratio, the pressure... 

    Numerical Investigation of Nano-Particles Dispersion and Deposition in Curved and Bifurcating Channels using Lattice Boltzmann Method

    , M.Sc. Thesis Sharif University of Technology Tehrani Saleh, Ali (Author) ; Moosavi, Ali (Supervisor)
    Abstract
    Investigation of transport and deposition of aerosol particles attracts interests in many fields of sciences. Various numerical and computational methods has been utilized in particulate flows studies. In recent relevant researches lattice Boltzmann method has been widely used and is reported to be a robust and efficient method. In present study, numerical investigation of dispersion and deposition of aerosol particles is performed in curved and bifurcating channels using LBM. Fluid flow simulations are performed using LBM while one-way coupling Lagrangian point of view is used for particle tracking. As the first showcase, transport and deposition of aerosol particles in channel flow with...