刘海湖 教授
 部门：能源与动力工程学院
 电话：13630283538
 ResearcherID：B20972013
 ORCID：0000000202951251
 论文：11 篇
 WOS被引：115 次
刘海湖，教授，博导。流体机械及工程系。能源与动力工程学院。入选西安交通大学青年拔尖人才支持计划。
 已选条件:
 1

 Colorgradient lattice Boltzmann modeling of immiscible twophase flows on partially wetting surfaces
 [期刊] PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART CJOURNAL OF MECHANICAL ENGINEERING SCIENCE, 2018, 232(3): 416430 SCIE SCOPUS
 被引用 1 (Web of Science℠)

摘要A zerointerfacialforce condition is derived and implemented to improve the wetting boundary scheme for a lattice Boltzmann colorgradient model. This new wetting boundary scheme is validated by two static problems, i.e. a droplet resting on a flat surface and a cylindrical surface, and one dynamic problem, i.e. the capillary filling in a twodimensional channel. In these simulations, we observe that nonphysical mass transfer is suppressed and spurious velocities become smaller. Meanwhile, accurate results including dynamic contact line movement are achieved for a broad range of contact angles. The model is then applied to study the displacement of immiscible fluids in a twodimensional channel. Both the displacement velocity and the change rate of finger length are found to exhibit a linear dependence on the contact angle at the viscosity ratio of unity. The displacement velocity decreases but the change rate of finger length increases with increasing capillary number, while the displacement velocity tends to be constant, i.e. twothirds of the maximum inlet velocity, at high viscosity ratios or low capillary numbers. In contrast to the displacement velocity, the change rate of finger length is negligible at high viscosity ratios or low capillary numbers, where the finger length is in an equilibrium state, while the equilibrium finger length itself is smaller at a higher viscosity ratio or a lower capillary number.关键词immiscible displacement , contact line movement , wetting boundary scheme , interfacial force , Colorgradient lattice Boltzmann model
 2

 A hybrid lattice Boltzmann and finite difference method for droplet dynamics with insoluble surfactants
 [期刊] JOURNAL OF FLUID MECHANICS, 2018, 837(): 381412 SCIE SCOPUS
 被引用 1 (Web of Science℠)

摘要Droplet dynamics in microfluidic applications is significantly influenced by surfactants. It remains a research challenge to model and simulate droplet behaviour including deformation, breakup and coalescence, especially in the confined microfluidic environment. Here, we propose a hybrid method to simulate interfacial flows with insoluble surfactants. The immiscible twophase flow is solved by an improved lattice Boltzmann colourgradient model which incorporates a Marangoni stress resulting from nonuniform interfacial tension, while the convectiondiffusion equation which describes the evolution of surfactant concentration in the entire fluid domain is solved by a finite difference method. The lattice Boltzmann and finite difference simulations are coupled through an equation of state, which describes how surfactant concentration influences interfacial tension. Our method is first validated for the surfactantladen droplet deformation in a threedimensional (3D) extensional flow and a 2D shear flow, and then applied to investigate the effect of surfactants on droplet dynamics in a 3D shear flow. Numerical results show that, at low capillary numbers, surfactants increase droplet deformation, due to reduced interfacial tension by the average surfactant concentration, and nonuniform effects from nonuniform capillary pressure and Marangoni stresses. The role of surfactants on the critical capillary number (Cacr) of droplet breakup is investigated for various confinements (defined as the ratio of droplet diameter to wall separation) and Reynolds numbers. For clean droplets, Cacr first decreases and then increases with confinement, and the minimum value of Cacr is reached at a confinement of 0.5; for surfactantladen droplets, Cacr exhibits the same variation in trend for confinements lower than 0.7, but, for higher confinements, Cacr is almost a constant. The presence of surfactants decreases Cacr for each confinement, and the decrease is also attributed to the reduction in average interfacial tension and nonuniform effects, which are found to prevent droplet breakup at low confinements but promote breakup at high confinements. In either clean or surfactantladen cases, Cacr first remains almost unchanged and then decreases with increasing Reynolds number, and a higher confinement or Reynolds number favours ternary breakup. Finally, we study the collision of two equalsized droplets in a shear flow in both surfactantfree and surfactantcontaminated systems with the same effective capillary numbers. It is identified that the nonuniform effects in the nearcontact interfacial region immobilize the interfaces when two droplets are approaching each other and thus inhibit their coalescence.关键词breakup/coalescence , computational methods , capillary flows
 3

 Comparative study of the discrete velocity and lattice Boltzmann methods for rarefied gas flows through irregular channels
 [期刊] PHYSICAL REVIEW E, 2017, 96(2): EI SCIE SCOPUS PubMed
 被引用 8 (Web of Science℠)

摘要Rooted from the gas kinetics, the lattice Boltzmann method (LBM) is a powerful tool in modeling hydrodynamics. In the past decade, it has been extended to simulate rarefied gas flows beyond the NavierStokes level, either by using the highorder GaussHermite quadrature, or by introducing the relaxation time that is a function of the gaswall distance. While the former method, with a limited number of discrete velocities (e.g., D2Q36), is accurate up to the early transition flow regime, the latter method (especially the multiple relaxation time (MRT) LBM), with the same discrete velocities as those used in simulating hydrodynamics (i.e.,D2Q9), is accurate up to the freemolecular flow regime in the planar Poiseuille flow. This is quite astonishing in the sense that less discrete velocities are more accurate. In this paper, by solving the BhatnagarGrossKrook kinetic equation accurately via the discrete velocity method, we find that the highorder GaussHermite quadrature cannot describe the large variation in the velocity distribution function when the rarefaction effect is strong, but the MRTLBM can capture the flow velocity well because it is equivalent to solving the NavierStokes equations with an effective shear viscosity. Since the MRTLBM has only been validated in simple channel flows, and for complex geometries it is difficult to find the effective viscosity, it is necessary to assess its performance for the simulation of rarefied gas flows. Our numerical simulations based on the accurate discrete velocity method suggest that the accuracy of the MRTLBM is reduced significantly in the simulation of rarefied gas flows through the rough surface and porous media. Our simulation results could serve as benchmarking cases for future development of the LBM for modeling and simulation of rarefied gas flows in complex geometries.关键词
 4

 A lattice Boltzmann method for axisymmetric thermocapillary flows
 [期刊] INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, 2017, 104(): 337350 EI SCIE SCOPUS
 被引用 14 (Web of Science℠)

摘要In this work, we develop a twophase lattice Boltzmann method (LBM) to simulate axisymmetric thermocapillary flows. This method simulates the immiscible axisymmetric twophase flow by an improved colorgradient model, in which the singlephase collision, perturbation and recoloring operators are all presented with the axisymmetric effect taken into account in a simple and computational consistent manner. An additional lattice Boltzmann equation is introduced to describe the evolution of the axisymmetric temperature field, which is coupled to the hydrodynamic equations through an equation of state. This method is first validated by simulations of RayleighBenard convection in a vertical cylinder and thermocapillary migration of a deformable droplet at various Marangoni numbers. It is then used to simulate the thermocapillary migration of two spherical droplets in a constant applied temperature gradient along their line of centers, and the influence of the Marangoni number (Ca), initial distance between droplets (S0), and the radius ratio of the leading to trailing droplets (A) on the migration process is systematically studied. As Ma increases, the thermal wake behind the leading droplet strengthens, resulting in the transition of the droplet migration from coalescence to noncoalescence; and also, the final distance between droplets increases with Ma for the noncoalescence cases. The variation of,S0 does not change the final state of the droplets although it has a direct impact on the migration process. In contrast, A can significantly influence the migration process of both droplets and their final state: at low Ma, decreasing A favors the coalescence of both droplets; at high Ma, the two droplets do not coalesce eventually but migrate with the same velocity for the small values of A, and decreasing A leads to a shorter equilibrium time and a faster migration velocity. (C) 2016 Elsevier Ltd. All rights reserved.关键词Lattice Boltzmann method , Droplet interactions , Marangoni number , Thermocapillary migration , Axisymmetric thermal flow
 5

 Lattice Boltzmann simulation of immiscible twophase flow with capillary valve effect in porous media
 [期刊] WATER RESOURCES RESEARCH, 2017, 53(5): 37703790 EI SCIE SCOPUS
 被引用 8 (Web of Science℠)

摘要A new algorithm for imposing the contact angle on solid surfaces is proposed in the Lattice Boltzmann colorgradient model. The capability and accuracy of this algorithm are validated by simulation of contact angles for a droplet resting on a flat surface and on a cylindrical surface. The colorgradient model with the proposed contact angle algorithm is then used to study the capillary valve effect in porous media. As a preliminary study, the capillary valve effect is explained by simulating immiscible twophase displacement within a singlepore geometry. It is shown that the capillary valve effect is accurately captured by the present simulations. Further simulations of drainage and imbibition are also conducted to understand the capillary valve effect in an experimentmatched porenetwork micromodel. The simulated results are found to agree quantitatively with the experimental results reported in literature, except for a few differences which result from the exclusion of contact angle hysteresis in the proposed algorithm.关键词Lattice Boltzmann method , contact angle hysteresis , multiphase flow , wetting boundary condition , porescale simulation , capillary valve effect
 6

 Threedimensional phasefield lattice Boltzmann model for incompressible multiphase flows
 [其他] 24th International Conference on Discrete Simulation of Fluid Dynamics (DSFD), 2016 : 340356 EI CPCIS SCIE SCOPUS
 被引用 5 (Web of Science℠)

摘要In this work, a phasefieldbased multiplerelaxationtime lattice Boltzmann (LB) model is developed to simulate threedimensional (3D) multiphase flows with moderate density ratio. Inspired by the work of Liang et al. [H. Liang, B. C. Shi, Z. L. Guo, Z. H. Chai, Phasefieldbased multiplerelaxationtime lattice Boltz Mann model for incompressible multiphase flows, Phys. Rev. E, 89(2014) 053320.], a timedependent source term is added in the LB equation for interface so that the 3D CahnHilliard equation can be recovered precisely. The NavierStokes equations are solved by introducing a pressure distribution function, which helps reduce the discretization errors in calculation of density gradient thereby improving the numerical stability for variable density. An interfacial force of potential form is utilized to effectively suppress spurious velocities at the interface and is incorporated into the LB equation as an additional body force. The present 3D model is tested by several classic numerical examples including the solid body rotation, the stationary droplet test, the droplet deformation and breakup in a simple shear flow and the RayleighTaylor instability. Simulation results are shown to be in good agreement with theoretical predictions, available experimental or numerical data, demonstrating a good capability of the present model in capturing the interface, dealing with topological changes, and simulating variable density ratio. In addition, it is interestingly found that the RayleighTaylor instability will be totally suppressed when the Weber number does not exceed a critical value. (C) 2016 Elsevier B.V. All rights reserved.关键词Phasefield model , Lattice Boltzmann method , Multiple relaxation time , Interfacial force , Multiphase flow
 7

 Threedimensional lattice Boltzmann simulations of microdroplets including contact angle hysteresis on topologically structured surfaces
 [其他] 24th International Conference on Discrete Simulation of Fluid Dynamics (DSFD), 2016 : 418430 EI CPCIS SCIE SCOPUS
 被引用 2 (Web of Science℠)

摘要In this study, the dynamical behavior of a droplet on topologically structured surface is investigated by using a threedimensional colorgradient lattice Boltzmann model. A wetting boundary condition is proposed to model fluidsurface interactions, which is advantageous to improve the accuracy of the simulation and suppress spurious velocities at the contact line. The model is validated by the droplet partial wetting test and reproduction of the Cassie and Wenzel states. A series of simulations are conducted to investigate the behavior of a droplet when subjected to a shear flow. It is found that in Cassie state, the droplet undergoes a transition from stationary, to slipping and finally to detachment states as the capillary number increases, while in Wenzel state, the last state changes to the breakup state. The critical capillary number, above which the droplet slipping occurs, is small for the Cassie droplet, but is significantly enhanced for the Wenzel droplet due to the increased contact angle hysteresis. In Cassie state, the receding contact angle nearly equals the prediction by the Cassie relation, and the advancing contact angle is close to 180, leading to a small contact angle hysteresis. In Wenzel state, however, the contact angle hysteresis is extremely large (around 100). Finally, high droplet mobility can be easily achieved for Cassie droplets, whereas in Wenzel state, extremely low droplet mobility is identified. (C) 2016 Elsevier B.V. All rights reserved.关键词Wenzel state , Structured surfaces , Lattice Boltzmann method , Cassie state , Contact angle hysteresis
 8

 Droplet dynamics in confinement
 [其他] 24th International Conference on Discrete Simulation of Fluid Dynamics (DSFD), 2016 : 463474 EI CPCIS SCIE SCOPUS
 被引用 7 (Web of Science℠)

摘要This study is to understand confinement effect on the dynamical behaviour of a droplet immersed in an immiscible liquid subjected to a simple shear flow. The lattice Boltzmann method, which uses a forcing term and a recolouring algorithm to realize the interfacial tension effect and phase separation respectively, is adopted to systematically study droplet deformation and breakup in confined conditions. The effects of capillary number, viscosity ratio of the droplet to the carrier liquid, and confinement ratio are studied. The simulation results are compared against the theoretical predictions, experimental and numerical data available in literature. We find that increasing confinement ratio will enhance deformation, and the maximum deformation occurs at the viscosity ratio of unity. The droplet is found to orient more towards the flow direction with increasing viscosity ratio or confinement ratio. Also, it is noticed that the wall effect becomes more significant for the confinement ratios larger than 0.4. Finally, the critical capillary number, above which the droplet breakup occurs, is found to be mildly affected by the confinement for the viscosity ratio of unity. Upon increasing the confinement ratio, the critical capillary number increases for the viscosity ratios less than unity, but decreases for the viscosity ratios more than unity. (C) 2016 The Authors. Published by Elsevier B.V.关键词Droplet dynamics , Lattice Boltzmann method , Confinement , Deformation , Breakup
 9

 A lattice Boltzmann method for axisymmetric multicomponent flows with high viscosity ratio
 [期刊] JOURNAL OF COMPUTATIONAL PHYSICS, 2016, 327(): 873893 EI SCIE SCOPUS
 被引用 4 (Web of Science℠)

摘要A colorgradient lattice Boltzmann method (LBM) is proposed to simulate axisymmetric multicomponent flows. This method uses a collision operator that is a combination of three separate parts, namely singlecomponent collision operator, perturbation operator, and recoloring operator. A source term is added into the singlecomponent collision operator such that in each singlecomponent region the axisymmetric continuity and momentum equations can be exactly recovered. The interfacial tension effect is realized by the perturbation operator, in which an interfacial force of axisymmetric form is derived using the concept of continuum surface force. A recoloring operator proposed by LatvaKokko and Rothman is extended to the axisymmetric case for phase segregation and maintenance of the interface. To enhance the method's numerical stability for handling binary fluids with high viscosity ratio, a multiplerelaxationtime model is used for the collision operator. Several numerical examples, including static droplet test, oscillation of a viscous droplet, and breakup of a liquid thread, are presented to test the capability and accuracy of the proposed colorgradient LBM. It is found that the present method is able to accurately capture the phase interface and produce low spurious velocities. Also, the LBM results are all in good agreement with the analytical solutions and/or available experimental data for a very broad range of viscosity ratios. (C) 2016 Elsevier Inc. All rights reserved.关键词Lattice Boltzmann method , Rayleigh instability , Axisymmetric flow , High viscosity ratio , Colorgradient model
 10

 Multiphase lattice Boltzmann simulations for porous media applications
 [期刊] COMPUTATIONAL GEOSCIENCES, 2016, 20(4): 777805 SCIE SCOPUS
 被引用 63 (Web of Science℠)

摘要Over the last two decades, lattice Boltzmann methods have become an increasingly popular tool to compute the flow in complex geometries such as porous media. In addition to single phase simulations allowing, for example, a precise quantification of the permeability of a porous sample, a number of extensions to the lattice Boltzmann method are available which allow to study multiphase and multicomponent flows on a pore scale level. In this article, we give an extensive overview on a number of these diffuse interface models and discuss their advantages and disadvantages. Furthermore, we shortly report on multiphase flows containing solid particles, as well as implementation details and optimization issues.关键词Lattice Boltzmann method , Porous media , Pore scale simulation
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 24th International Conference on Discrete Simulation of Fluid Dynamics (DSFD)(3)
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 INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER(1)
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