检索结果-南通市图书馆

Modeling of finite-size droplets and particles in multiphase flows

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2015年第4期28卷 974-982页

作者： Prashant Khare Shanwu Wang Vigor Yang School of Aerospace Engineering Georgia Institute of Technology

The conventional point-particle approach for treating the dispersed phase in a continuous flowfield is extended by taking into account the effect of finite particle size, using a Gaussian interpolation from Lagrangian points to the Eulerian field.The inter-phase exchange terms in the conservation equations are distributed over the volume encompassing the particle size, as opposed to the Dirac delta function generally used in the point-particle approach.The proposed approach is benchmarked against three different flow configurations in a numerical framework based on large eddy simulation（LES） turbulence closure.First, the flow over a circular cylinder is simulated for a Reynolds number of 3900 at 1 atm pressure.Results show good agreement with experimental data for the mean streamwise velocity and the vortex shedding frequency in the wake region.The calculated flowfield exhibits correct physics, which the conventional point-particle approach fails to capture.The second case deals with diesel jet injection in quiescent environment over a pressure range of 1.1–5.0 MPa.The calculated jet penetration depth closely matches measurements.It decreases with increasing chamber pressure, due to enhanced drag force in a denser fluid environment.Finally, water and acetone jet injection normal to air crossflow is studied at1 atm.The calculated jet penetration and Sauter mean diameter of liquid droplets compare very well with measurements.

关键词： droplets Finite-size effects Large eddy simulation Multiphase flow Particle-laden flow

Microfluidic fabrication of water-in-water droplets encapsulated in hydrogel microfibers

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2019年第2期30卷 457-460页

作者： Chenguang Liu Wenchen Zheng Ruoxiao Xie Yupeng Liu Zhe Liang Guoan Luo Mingyu Ding Qionglin Liang Key Laboratory of Chemical Biology (Ministry of Education) Beijing Key Laboratory of Microanalytical Methods ξ Instrumentation Department of Chemistry Tsinghua University State Key Laboratory of Quality Research in Chinese Medicine Macao Institute for Applied Research in Medicine and Health Macao University of Science and Technology

Aqueous microdroplets are of significant interest in biological fields, while the employment of water-inoil (w/o) emulsion and lack of spatial control precluded its widespread application. Herein a novel microfluidic approach is developed to generate water-in-water (w/w) microdroplets embedded in hydrogel microfibers. Aqueous two phase system (ATPS) is applied to generate w/w droplets, and alginate is introduced to continuous phase to form microfibers, which offers spatial restriction and manipulation possibility to droplets. The size and pattern of aqueous droplets can be precisely controlled, and immobilization within hydrogel fiber facilitates easy manipulation and observation. The microdroplets surrounded by hydrophilic environment can act as a cell-cell interaction model, and their potential for biological and environmental applications are demonstrated by long-term culture of encapsulated cells and water remediation of Bacillus subtilis.

关键词： Microfluidics Water-in-water droplets Droplet fibers Intercellular communication Water remediation

Transporting droplets through surface anisotropy

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Microsystems & Nanoengineering 2015年第1期1卷 74-81页

作者： Hal R.Holmes Karl F.Böhringer Department of Bioengineering University of WashingtonSeattleWA 98195USA Department of Electrical Engineering University of WashingtonSeattleWA 98195USA

This review article examines digital microfluidic systems that manipulate droplets through surface anisotropy.These systems are categorized as surface tension driven or contact line driven.Surface tension driven systems include electrowetting on dielectric,Marangoni flow on microheater arrays,and chemical gradient surfaces,whereas contact line driven systems include anisotropic ratchet conveyors,nanostructured Parylene ratchets,and tilted pillar arrays.This article describes the operating principles and outlines the fabrication procedures for each system.We also present new equations that unify several previous models of contact line driven systems.The strengths and weaknesses of each system are compared,with a focus on their ability to perform the generation,switching,fusion,and fission of droplets.Finally,we discuss current and potential future applications of these systems.

关键词： droplets digital microfluidics electrowetting thermocapillary forces contact line oscillation

The histone methyltransferase SUVR2 promotes DSB repair via chromatin remodeling and liquidliquid phase separation

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Molecular Plant 2022年第7期15卷 1157-1175页

作者： Qianwen Liu Peng Liu Tuo Ji Lihua Zheng Chen Shen Shasha Ran Jinling Liu Yafei Zhao Yiding Niu Tao Wang Jiangli Dong State Key Laboratory of Agrobiotechnology College of Biological SciencesChina Agricultural UniversityBeijing 100193China Key Laboratory of Forage and Endemic Crop Biology Ministry of EducationSchool of Life SciencesInner Mongolia UniversityHohhotChina

Maintaining genomic integrity and stability is particularly important for stem cells,which are at the top of the cell lineage origin.Here,we discovered that the plant-specific histone methyltransferase SUVR2 maintains the genome integrity of the root tip stem cells through chromatin remodeling and liquid-liquid phase separation(LLPS)when facing DNA double-strand breaks(DSBs).The histone methyltransferase SUVR2(MtSUVR2)has histone methyltransferase activity and catalyzes the conversion of histone H3 lysine 9 monomethylation(H3K9me1)to H3K9me2/3 in vitro and in Medicago truncatula.Under DNA damage,the proportion of heterochromatin decreased and the level of DSB damage marker y-H2AX increased in suvr2 mutants,indicating that MtSUVR2 promotes the compaction of the chromatin structure through H3K9 methylation modification to protect DNA from damage.Interestingly,MtSUVR2 was induced by DSBs to phase separate and form droplets to localize at the damage sites,and this was confirmed by immunofluorescence and fluorescence recovery after photobleaching experiments.The IDR1 and lowcomplexity domain regions of MtSUVR2 determined its phase separation in the nucleus,whereas the IDR2 region determined the interaction with the homologous recombinase MtRAD51.Furthermore,we found that MtSUVR2 drove the phase separation of MtRAD51 to form"DNA repair bodies,"which could enhance the stability of MtRAD51 proteins to facilitate error-free homologous recombination repair of stem cells.Taken together,our study reveals that chromatin remodeling-associated proteins participate in DNA repair through LLPS.

关键词： stem cell droplets H3K9me2 SUVR2 Medicago truncatula

Mathematical modeling of icing process of the outer surface of the hull for a marine vessel

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2023年第2期35卷 232-239页

作者： Konstantin Koshelev Andrey Osipov Sergei Strijhak Nikita Tryaskin ISP RAS MoscowRussia Saint-Petersburg State Marine Technical University Saint-PetersburgRussia

The task of studying the process of icing is important due to the operation of large ships and fishing vessels in the seas of the Arctic Ocean.In this paper the ice accretion simulation for fishing vessel has been done at different Reynolds and Froude numbers.A hybrid approach was used for modeling:first,the approach based on Reynolds-averaged Navier-Stokes(RANS)model and volume of fluid(VOF)method with interDyMFoam solver was used for ship modelling in waves,second,RANS model and Euler-Lagrangian approach with iceFoam solver for ice accretion process modelling for ship with hull was applied.The k-ωSST turbulence model with wall functions was used for the RANS model.With the help of the interDyMFoam solver,the position of water jet and liquid droplets in space were determined during the movement of the ship and taking into account the waves in the sea.With the help of iceFoam solver,the process of ice accretion on the surface of the vessel was modeled.The calculations were run for different number Reynolds,Froude.The analysis of mesh convergency was done.The distribution of ice thickness and water film on the ship’s surface is obtained.The simulations were performed on a high-performance cluster in parallel mode.

关键词： Ship sea safety climate movement modelling turbulence model water spray droplets velocity ice film mass

Does the Homogeneous Ice Nucleation Initiate in the Bulk Volume or at the Surface of Super-Cooled Water droplets? A Review

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Atmospheric and Climate Sciences 2014年第4期4卷 653-664页

作者： Gianni Santachiara Franco Belosi Institute of Atmospheric Sciences and Climate (ISAC) Italian National Research Council Bologna Italy

The formation of ice in clouds can occur through primary processes, either homogeneously or heterogeneously triggered by aerosol particles called ice nuclei, as well as through secondary processes. The homogeneous ice nucleation process involves only pure water or solution droplets. Homogeneous freezing is crucial for the microphysics in the formation of high-altitude cirrus and polar stratospheric clouds, and also in the glaciation of thunderclouds, at temperatures below about 235 K. Nucleation rates in supercooled water have been measured using different experimental techniques: expansion cloud chambers, water-in-oil emulsions, levitation methods, free falling droplets, supersonic nozzles, field measurements, and molecular dynamics simulations. An important question concerns the possibility that the nucleation process in supercooled water can occur not only in the interior volume of the droplet, but even at or close to its surface. Even if there is no conclusive evidence, the majority of experimental and theoretical results suggest that the contribution of surface nucleation increases with decreasing radius of the supercooled droplets, and the surface (or sub-surface) nucleation rate is prevalent for droplets with radius lower than about 5 μm. If homogeneous freezing initiates at the droplet surface, the freezing rate should depend on the droplet size, and even a slight contamination by molecules within the surface layer could hamper the rate of the nucleation process.

关键词： Supercooled droplets Homogeneous Nucleation Nucleation Rate

Numerical Simulation of Water droplets Deposition on the Last-Stage Stationary Blade of Steam Turbine

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Energy and Power Engineering 2010年第4期2卷 248-253页

作者： Danmei Xie Xinggang Yu Wangfan Li Youmin Hou Yang Shi Sun Cai 不详

Based on the method of discrete phase, the law of droplets’ deposition in the last stage stationary blade of a supercritical 600 MW Steam Turbine is simulated in the first place of this paper by using the Wet-steam model in commercial software FLUENT, where the influence of inlet angle of water droplets of the stationary blades is also considered. Through the calculation, the relationship between the deposition and the diameter of water droplets is revealed. Then, the amount of droplets deposition in the suction and pressure surface is derived. The result is compared with experimental data and it proves that the numerical simulation result obtained in this paper is reasonable. Finally, a formula of the relationship between the diameter of water droplets and the inlet angle is fit, which could be used for approximate calculation in the engineering applications.

关键词： Steam Turbine Stationary Blade Wet Steam Water droplets Deposition Discrete Phase Numerical Simulation

Modeling Evaporating droplets in Complex Unsteady Flows

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Open Journal of Fluid Dynamics 2012年第2期2卷 35-43页

作者： Sandip Ghosal Sourabh V. Apte Department of Mechanical Engineering Northwestern University Evanston USA School of Mechanical Industrial and Manufacturing Engineering Oregon State University Corvallis USA

In many applications, a moving fluid carries a suspension of droplets of a second phase which may change in size due to evaporation or condensation. Examples include liquid fuel drops in engines and raindrops or ice-crystals in a thunderstorm. If the number of such particles is very large, and, if further, the flow is inhomogeneous, unsteady or turbulent, it may be practically impossible to explicitly compute all of the fluid and particle degrees of freedom in a numerical simulation of the system. Under such circumstances Lagrangian Particle Tracking (LPT) of a small subset of the particles is used to reduce the computational effort. The purpose of this paper is to compare the LPT with an alternate method that is based on an approximate solution of the conservation equation of particle density in phase space by the method of moments (MOM). Closure is achieved by invoking the assumption that the droplet size distribution is locally lognormal. The resulting coupled transport equations for the local mean and variance of the particle size distribution are then solved in conjunction with the usual equations for the fluid and associated scalar fields. The formalism is applied to the test case of a uniform distribution of droplets placed in a non homogeneous temperature field and stirred with a decaying Taylor vortex. As a benchmark, we perform a direct numerical simulation (DNS) of high resolution that keeps track of all the particles together with the fluid flow.

关键词： Method of Moments Point-Particles droplets Sprays Two-Phase Turbulent Flows

Interaction of Surfactants and Polyelectrolyte-Coated Liquid Crystal droplets

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science and Chemical Engineering 2014年第11期2卷 1-7页

作者： Tanmay Bera Jiyu Fang Department of Materials Science and Engineering University of Central Florida Orlando USA

It is known that the adsorption of surfactants at the liquid crystal (LC)/aqueous interface can induce a bipolar-to-radial director configuration of LC droplets dispersed in aqueous solution. In this paper, we study the effect of charged polyelectrolyte-coating on the interaction of surfactants and LC droplet cores by observing the director configuration of the LC droplet cores as a function of surfactant concentrations. It is found that surfactants can penetrate into the polyelectrolyte coating and react with the LC droplet cores to induce the bipolar-to-radial transition of the LC inside the droplet cores. However, the concentration of charged surfactants required to induce the configuration transition of the LC droplet cores is affected by the charged polyelectrolyte coating. The effect is significantly enlarged with decreasing the alkyl chain length of charged surfactants. Our results highlight the possibility of engineering polyelectrolyte coatings to tune the interaction of LC droplets with analysts, which is critical towards designing LC droplet based sensors.

关键词： Liquid Crystals droplets Polyelectrolyte Coatings Surfactants Configuration Transitions