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Lattice Boltzmann 2038

EPL 2015年第5期109卷

作者： Succi, Sauro Ist Applicaz Calcolo I-00185 Rome Italy Harvard Univ Inst Appl Computat Sci Cambridge MA 02138 USA

Based on the past twenty-five years of lattice Boltzmann research, we venture into a far-flung prediction for the next twenty-five, with past and future privileged over the present state of affairs. Copyright (C) EPLA... 详细信息

关键词： computational methods in statistical physics and nonlinear dynamics Kinetic theory computational methods in fluid dynamics

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New modified weight function for the dissipative force in the DPD method to increase the Schmidt number

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EPL 2015年第2期110卷

作者： Yaghoubi, S. Shirani, E. Pishevar, A. R. Afshar, Y. Isfahan Univ Technol Dept Mech Engn Esfahan *** Iran Foolad Inst Technol Fooladshahr Isfahan Iran Max Planck Inst Mol Cell Biol & Genet D-01307 Dresden Germany

To simulate liquid fluid flows with high Schmidt numbers (Sc), one needs to use a modified version of the Dissipative Particle dynamics (DPD) method. Recently the modifications made by others for the weight function of dissipative forces, enables DPD simulations for Sc, up to 10. In this paper, we introduce a different dissipative force weight function for DPD simulations that allows achieving a solution with higher values of Sc and improving the dynamic characteristics of the simulating fluid. Moreover, by reducing the energy of DPD particles, even higher values of Sc can be achieved. Finally, using the new proposed weight function and k(B)T = 0.2, the Sc values can reach up to 200. Copyright (C) EPLA, 2015

关键词： computational methods in fluid dynamics computational techniques, simulations Classical statistical mechanics

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Thermodynamic-consistent lattice Boltzmann model for nonideal fluids

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EPL 2015年第4期112卷

作者： Wen, Binghai Qin, Zhangrong Zhang, Chaoying Fang, Haiping Guangxi Normal Univ Guangxi Key Lab Multisource Informat Min & Secur Guilin 541004 Peoples R China Chinese Acad Sci Shanghai Inst Appl Phys Div Interfacial Water Shanghai 201800 Peoples R China Chinese Acad Sci Shanghai Inst Appl Phys Key Lab Interfacial Phys & Technol Shanghai 201800 Peoples R China Chinese Acad Sci Shanghai Sci Res Ctr Shanghai 201204 Peoples R China

A lattice Boltzmann model to simulate phase separation and two-phase flow is proposed. The nonideal force in multiphase flow is directly computed from the free energy. Thermodynamic consistency and Galilean invariance are theoretically analyzed and numerically verified. Remarkably, the theoretical simplicity endues the model with the advantages of high efficiency and easy implementation. We also find that it can work well together with various equations of state in order to simulate different kinds of multiphase flows. Importantly, it has a tunable parameter., which can be used to reduce the effect of spurious current and adjust the surface tension to meet the requirements of researches. Copyright (C) EPLA, 2015

关键词： computational methods in fluid dynamics Thermodynamic functions and equations of state Surface tension and related phenomena

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Derivation of model kinetic equation

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EPL 2015年第4期111卷

作者： Belyi, V. V. Russian Acad Sci IZMIRAN Moscow 142190 Russia

A new form of the model collision operator is derived. One-component and many component systems are considered. The collision operator proposed takes properly into account the relaxation of the first 13 hydrodynamic moments. A technique for construction of the model collision integral based on a known expression for the linearized model operator is proposed. It is shown that, within our model, the model collision operator does not contain the complicated exponential, common for ellipsoidal statistical models. Boltzmann's H-theorem is proved for our model. Copyright (C) EPLA, 2015

关键词： Kinetic theory computational methods in fluid dynamics Plasma simulation

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Numerical simulation of flows past flat plates using volume penalization

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computational & APPLIED MATHEMATICS 2014年第2期33卷 481-495页

作者： Schneider, Kai Paget-Goy, Mickael Verga, Alberto Farge, Marie Aix Marseille Univ CNRS M2P2 F-13541 Marseille 20 France Aix Marseille Univ CNRS IM2NP F-13397 Marseille 20 France Ecole Normale Super LMD CNRS F-75231 Paris 05 France

We present numerical simulations of two-dimensional viscous incompressible flows past flat plates having different kind of wedges: one tip of the plate is rectangular, while the other tip is either a wedge with an angle of or a round shape. We study the shear layer instability of the flow considering different scenarios, either an impulsively started plate or an uniformly accelerated plate, for Reynolds number . The volume penalization method, with either a Fourier spectral or a wavelet discretization, is used to model the plate geometry with no-slip boundary conditions, where the geometry of the plate is simply described by a mask function. On both tips, we observe the formation of thin shear layers which are rolling up into spirals and form two primary vortices. The self-similar scaling of the spirals corresponds to the theoretical predictions of Saffman for the inviscid case. At later times, these vortices are advected downstream and the free shear layers undergo a secondary instability. We show that their formation and subsequent dynamics is highly sensitive to the shape of the tips. Finally, we also check the influence of a small riblet, added on the back of the plate on the flow evolution.

关键词： Instability of shear layers Vortex dynamics computational methods in fluid dynamics Free shear layers Wavelets Spectral methods

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Magnetocoalescence of ferrofluid droplets in a flat microfluidic channel

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EPL 2014年第2期106卷

作者： Kadivar, Erfan Persian Gulf Univ Fac Sci Dept Phys Bushehr 75168 Iran Max Planck Inst Dynam & Selforg D-37077 Gottingen Germany

In this work we present the numerical study of the deformation and the coalescence of two ferrofluid droplets in a uniform applied magnetic field. Employing the boundary element method (BEM), we numerically solve the Darcy equation in a flat microfluidic channel by applying the magnetic normal stress as a boundary condition at the interfaces of droplets. The occurrence of different numerical regimes is summarized in the two phase diagrams scanned by the distance between two droplets, magnetic capillary number, and magnetic permeability. We also show the existence of the critical separation of two droplets where the coalescence of the droplets is inhibited. This critical value is independent of the applied-magnetic-field intensity, although it depends on the permeability ratio of droplet and continuous phase. Copyright (C) EPLA, 2014

关键词： computational methods in fluid dynamics Effects of electric and magnetic fields Breakup and coalescence

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Aero-thermo-dynamic analysis of the SpaceLiner-7.1 vehicle in high altitude flight

Aero-thermo-dynamic analysis of the SpaceLiner-7.1 vehicle i...

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29th International Symposium on Rarefied Gas dynamics(第29届国际稀薄气体动力学会议)

作者： Gennaro Zuppardi Luigi Morsa Martin Sippel Tobias Schwanekamp Department of Industrial Engineering-Aerospace Division-University of Naples “Federico Ⅱ” Piazzale Tecchio 8080125 NaplesItaly Space Launcher System Analysis(SART)Deutsches Zentrum fur Luft-und Raumfahrt e.V.(DLR)28359 BremenGermany

ISBN: (纸本)9780735412651

SpaceLiner, designed by DLR, is a visionary, extremely fast passenger transportation concept. It consists of two stages: a winged booster, a vehicle. After separation of the two stages, the booster makes a controlled re-entry and returns to the launch site. According to the current project, version 7-1 of SpaceLiner (SpaceLiner-7.1), the vehicle should be brought at an altitude of 75 km and then released, undertaking the descent path. In the perspective that the vehicle of SpaceLiner-7.1 could be brought to altitudes higher than .75 km, e.g. 100 km or above and also for a speculative purpose, in this paper the aerodynamic parameters of the SpaceLiner-7.1 vehicle are calculated in the whole transition regime, from continuum low density to free molecular flows. Computer simulations have been carried out by three codes: two DSMC codes, DS3V in the altitude interval 100-250 km for the evaluation of the global aerodynamic coefficients and DS2V at the altitude of 60 km for the evaluation of the heat flux and pressure distributions along the vehicle nose, and the DLR HOTSOSE code for the evaluation of the global aerodynamic coefficients in continuum, hypersonic flow at the altitude of 44.6 km. The effectiveness of the flaps with deflection angle of -35 deg. was evaluated in the above mentioned altitude interval. The vehicle showed longitudinal stability in the whole altitude interval even with no flap. The global bridging formulae verified to be proper for the evaluation of the aerodynamic coefficients in the altitude interval 80-100 km where the computations cannot be fulfilled either by CFD, because of the failure of the classical equations computing the transport coefficients, or by DSMC because of the requirement of very high computer resources both in terms of the core storage (a high number of simulated molecules is needed) and to the very long processing time.

关键词： rarefied gas dynamics supersonic and hypersonic flows direct simulation Monte Carlo method computational methods in fluid dynamics rarefied gas dynamics hypersonic flow vehicle AERODYNAMIC COEFFICIENTS panel method (fluid dynamics) magnetic core stores launching sites transport properties BOOSTERS

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Two- and three-dimensional lattice Boltzmann simulations of particle migration in microchannels

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MICROfluidICS AND NANOfluidICS 2013年第6期15卷 785-796页

作者： Basagaoglu, H. Allwein, S. Succi, S. Dixon, H. Carrola, J. T., Jr. Stothoff, S. Southwest Res Inst Geosci & Engn Div San Antonio TX 78238 USA Southwest Res Inst Microencapsulat & Nanomat Dept San Antonio TX 78238 USA Inst Applicaz Calcolo I-00161 Rome Italy Southwest Res Inst Aerosp Elect Syst Engn & Training San Antonio TX 78238 USA

The use of two-dimensional (2D) numerical simulations with a reduced particle-based Reynolds number (Re) for studying particle migration in a microchannel with equally spaced multiple constrictions was investigated. 2D and 3D colloidal lattice Boltzmann (LB) models were used to simulate particle-fluid hydrodynamics. Experiments were conducted with inert microparticles in a creeping flow in a microflow channel with symmetric wall obstacles. Lowering Re in 2D simulations by a factor of R (the dimensionless particle radius in LB simulations) resulted in a close match between numerically computed and experimentally obtained particle velocities, indicating that Re-based dimensional scaling was needed to capture the 3D particle flow dynamics in 2D simulations of experimental data. We captured particle displacement motion in a microchannel with symmetric inline obstacles in 2D simulations, where symmetry in the flow field was broken by local disturbances in the flow field due to particle motion, indicating that asymmetry in channel geometry is not the sole cause for particle displacement motion. Particle acceleration/deceleration around each constriction followed the same pattern, but each constriction acted like a particle accelerator in 2D and 3D simulations, in which particles exhibited progressively higher velocities in each subsequent constriction. Particles migrated across multiple streamlines in converging and diverging flow zones in a creeping flow, which calls into question the use of steady streamlines for calculating transient particle flow. Monotonicity in particle acceleration toward the constriction and deceleration beyond the constriction was broken by interparticle hydrodynamic interactions leading to more pronounced particle migration across multiple streamlines.

关键词： computational methods in fluid dynamics Low Reynolds number (creeping) flows Hydrodynamics Hydraulics Hydrostatics

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Hydrodynamic ratchet: Controlled motion of a polymer in an alternating microchannel flow

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EPL 2013年第1期104卷

作者： Zhang, Zhen Stark, Holger Mikhailov, Alexander S. Univ Sci & Technol China Dept Chem Phys Hefei 230026 Anhui Peoples R China Tech Univ Berlin Inst Theoret Phys D-10623 Berlin Germany Fritz Haber Inst Max Plank Gesell Abt Phys Chem D-14195 Berlin Germany

Using ratchets, periodic or irregular oscillations can be transformed into steady translational or rotational motions. Here, we consider a model system that operates as a hydrodynamic ratchet. A polymer is placed inside a narrow channel where an oscillating Poiseuille flow is externally created. The ratchet mechanism is implemented by introducing a feedback control for the lateral position of the polymer through which its mobility becomes effectively dependent on the direction of its motion along the channel. We employ the semi-flexible elastic chain modeling for the polymer and use the method of multi-particle collision dynamics to simulate the fluid. We indeed observe directed motion of the polymer and determine the dependence of the propagation velocity on the model parameters. Copyright (C) EPLA, 2013

关键词： Micro- and nano- scale flow phenomena Polymers and polymer solutions computational methods in fluid dynamics

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Lattice BGK kinetic model for high-speed compressible flows: Hydrodynamic and nonequilibrium behaviors

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EPL 2013年第2期103卷

作者： Gan, Yanbiao Xu, Aiguo Zhang, Guangcai Yang, Yang North China Inst Aerosp Engn Langfang 065000 Peoples R China Inst Appl Phys & Computat Math Natl Key Lab Computat Phys Beijing 100088 Peoples R China China Petr Pipeline Bur Langfang 065000 Peoples R China

We present a simple and general approach to formulate the lattice BGK model for high-speed compressible flows. The main point consists of two parts: an appropriate discrete equilibrium distribution function (DEDF) f(eq) and a discrete velocity model with flexible velocity size. The DEDF is obtained by f(eq) = C M-1, where M is a set of moments of the Maxwellian distribution function, and C is the matrix connecting the DEDF and the moments. The numerical components of C are determined by the discrete velocity model. The calculation of C-1 is based on the analytic solution which is a function of the parameter controlling the sizes of discrete velocity. The choice of the discrete velocity model has a high flexibility. The specific-heat ratio of the system can be flexible. The approach works for the one-, two- and three-dimensional model constructions. As an example, we compose a new lattice BGK kinetic model which works not only for recovering the Navier-Stokes equations in the continuum limit but also for measuring the departure of the system from its thermodynamic equilibrium. Via adjusting the sizes of the discrete velocities, the stably simulated Mach number can be significantly increased up to 30 or even higher. The model is verified and validated by well-known benchmark tests. Some macroscopic behaviors of the system due to the deviation from thermodynamic equilibrium around the shock wave interfaces are shown. Copyright (C) EPLA, 2013

关键词： computational methods in fluid dynamics Kinetic and transport theory of gases Kinetic theory

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