The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Fumei Rong - One of the best experts on this subject based on the ideXlab platform.
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lattice bgk model for incompressible axisymmetric flows
Communications in Computational Physics, 2012Co-Authors: Ting Zhang, Zhenhua Chai, Fumei RongAbstract:In this paper, a lattice Boltzmann BGK (LBGK) model is proposed for simulating incompressible axisymmetric flows. Unlike other existing axisymmetric lattice Boltzmann models, the present LBGK model can eliminate the compressible effects only with the small Mach number limit. Furthermore the source terms of the model are simple and contain no velocity gradients. Through the Chapman-Enskog expansion, the Macroscopic Equations for incompressible axisymmetric flows can be exactly recovered from the present LBGK model. Numerical simulations of the Hagen-Poiseuille flow, the pulsatile Womersley flow, the flow over a sphere, and the swirling flow in a closed cylindrical cavity are performed. The results agree well with the analytic solutions and the existing numerical or experimental data reported in some previous studies.
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lattice bgk model for incompressible axisymmetric flows
Communications in Computational Physics, 2012Co-Authors: Ting Zhang, Zhenhua Chai, Fumei RongAbstract:In this paper, a lattice Boltzmann BGK (LBGK) model is proposed for simulating incompressible axisymmetric flows. Unlike other existing axisymmetric lattice Boltzmann models, the present LBGK model can eliminate the compressible effects only with the small Mach number limit. Furthermore the source terms of the model are simple and contain no velocity gradients. Through the Chapman-Enskog expansion, the Macroscopic Equations for incompressible axisymmetric flows can be exactly recovered from the present LBGK model. Numerical simulations of the Hagen-Poiseuille flow, the pulsatile Womersley flow, the flow over a sphere, and the swirling flow in a closed cylindrical cavity are performed. The results agree well with the analytic solutions and the existing numerical or experimental data reported in some previous studies.
Masud Mansuripur - One of the best experts on this subject based on the ideXlab platform.
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trouble with the lorentz law of force incompatibility with special relativity and momentum conservation
Physical Review Letters, 2012Co-Authors: Masud MansuripurAbstract:The Lorentz law of force is the fifth pillar of classical electrodynamics, the other four being Maxwell's Macroscopic Equations. The Lorentz law is the universal expression of the force exerted by electromagnetic fields on a volume containing a distribution of electrical charges and currents. If electric and magnetic dipoles also happen to be present in a material medium, they are traditionally treated by expressing the corresponding polarization and magnetization distributions in terms of bound-charge and bound-current densities, which are subsequently added to free-charge and free-current densities, respectively. In this way, Maxwell's Macroscopic Equations are reduced to his microscopic Equations, and the Lorentz law is expected to provide a precise expression of the electromagnetic force density on material bodies at all points in space and time. This Letter presents incontrovertible theoretical evidence of the incompatibility of the Lorentz law with the fundamental tenets of special relativity. We argue that the Lorentz law must be abandoned in favor of a more general expression of the electromagnetic force density, such as the one discovered by Einstein and Laub in 1908. Not only is the Einstein-Laub formula consistent with special relativity, it also solves the long-standing problem of "hidden momentum" in classical electrodynamics.
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nature of electric and magnetic dipoles gleaned from the poynting theorem and the lorentz force law of classical electrodynamics
Optics Communications, 2011Co-Authors: Masud MansuripurAbstract:Abstract Starting with the most general form of Maxwell's Macroscopic Equations in which the free charge and free current densities, ρ free and J free , as well as the densities of polarization and magnetization, P and M , are arbitrary functions of space and time, we compare and contrast two versions of the Poynting vector, namely, S = μ o − 1 E × B and S = E × H . Here E is the electric field, H is the magnetic field, B is the magnetic induction, and μ o is the permeability of free space. We argue that the identification of one or the other of these Poynting vectors with the rate of flow of electromagnetic energy is intimately tied to the nature of magnetic dipoles and the way in which these dipoles exchange energy with the electromagnetic field. In addition, the manifest nature of both electric and magnetic dipoles in their interactions with the electromagnetic field has consequences for the Lorentz law of force. If the conventional identification of magnetic dipoles with Amperian current loops is extended beyond Maxwell's Macroscopic Equations to the domain where energy, force, torque, momentum, and angular momentum are active participants, it will be shown that “hidden energy” and “hidden momentum” become inescapable consequences of such identification with Amperian current loops. Hidden energy and hidden momentum can be avoided, however, if we adopt S = E × H as the true Poynting vector, and also accept a generalized version of the Lorentz force law. We conclude that the identification of magnetic dipoles with Amperian current loops, while certainly acceptable within the confines of Maxwell's Macroscopic Equations, is inadequate and leads to complications when considering energy, force, torque, momentum, and angular momentum in electromagnetic systems that involve the interaction of fields and matter.
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maxwell s Macroscopic Equations the energy momentum postulates and the lorentz law of force
Physical Review E, 2009Co-Authors: Masud Mansuripur, Armis R ZakharianAbstract:We argue that the classical theory of electromagnetism is based on Maxwell's Macroscopic Equations, an energy postulate, a momentum postulate, and a generalized form of the Lorentz law of force. These seven postulates constitute the foundation of a complete and consistent theory, thus eliminating the need for actual (i.e., physical) models of polarization $\mathbf{P}$ and magnetization $\mathbf{M}$, these being the distinguishing features of Maxwell's Macroscopic Equations. In the proposed formulation, $\mathbf{P}(\mathbf{r},t)$ and $\mathbf{M}(\mathbf{r},t)$ are arbitrary functions of space and time, their physical properties being embedded in the seven postulates of the theory. The postulates are self-consistent, comply with the requirements of the special theory of relativity, and satisfy the laws of conservation of energy, linear momentum, and angular momentum. One advantage of the proposed formulation is that it sidesteps the long-standing Abraham-Minkowski controversy surrounding the electromagnetic momentum inside a material medium by simply ``assigning'' the Abraham momentum density $\mathbf{E}(\mathbf{r},t)\ifmmode\times\else\texttimes\fi{}\mathbf{H}(\mathbf{r},t)∕{c}^{2}$ to the electromagnetic field. This well-defined momentum is thus taken to be universal as it does not depend on whether the field is propagating or evanescent, and whether or not the host medium is homogeneous, transparent, isotropic, dispersive, magnetic, linear, etc. In other words, the local and instantaneous momentum density is uniquely and unambiguously specified at each and every point of the material system in terms of the $\mathbf{E}$ and $\mathbf{H}$ fields residing at that point. Any variation with time of the total electromagnetic momentum of a closed system results in a force exerted on the material media within the system in accordance with the generalized Lorentz law.
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electromagnetic force and torque in ponderable media
Optics Express, 2008Co-Authors: Masud MansuripurAbstract:Maxwell’s Macroscopic Equations combined with a generalized form of the Lorentz law of force are a complete and consistent set of Equations. Not only are these five Equations fully compatible with special relativity, they also conform with conservation laws of energy, momentum, and angular momentum. We demonstrate consistency with the conservation laws by showing that, when a beam of light enters a magnetic dielectric, a fraction of the incident linear (or angular) momentum pours into the medium at a rate determined by the Abraham momentum density, E × H/c2, and the group velocity Vg of the electromagnetic field. The balance of the incident, reflected, and transmitted momenta is subsequently transferred to the medium as force (or torque) at the leading edge of the beam, which propagates through the medium with velocity Vg. Our analysis does not require “hidden” momenta to comply with the conservation laws, nor does it dissolve into ambiguities with regard to the nature of electromagnetic momentum in ponderable media. The linear and angular momenta of the electromagnetic field are clearly associated with the Abraham momentum, and the phase and group refractive indices (np and ng) play distinct yet definitive roles in the expressions of force, torque, and momentum densities.
Ting Zhang - One of the best experts on this subject based on the ideXlab platform.
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lattice bgk model for incompressible axisymmetric flows
Communications in Computational Physics, 2012Co-Authors: Ting Zhang, Zhenhua Chai, Fumei RongAbstract:In this paper, a lattice Boltzmann BGK (LBGK) model is proposed for simulating incompressible axisymmetric flows. Unlike other existing axisymmetric lattice Boltzmann models, the present LBGK model can eliminate the compressible effects only with the small Mach number limit. Furthermore the source terms of the model are simple and contain no velocity gradients. Through the Chapman-Enskog expansion, the Macroscopic Equations for incompressible axisymmetric flows can be exactly recovered from the present LBGK model. Numerical simulations of the Hagen-Poiseuille flow, the pulsatile Womersley flow, the flow over a sphere, and the swirling flow in a closed cylindrical cavity are performed. The results agree well with the analytic solutions and the existing numerical or experimental data reported in some previous studies.
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lattice bgk model for incompressible axisymmetric flows
Communications in Computational Physics, 2012Co-Authors: Ting Zhang, Zhenhua Chai, Fumei RongAbstract:In this paper, a lattice Boltzmann BGK (LBGK) model is proposed for simulating incompressible axisymmetric flows. Unlike other existing axisymmetric lattice Boltzmann models, the present LBGK model can eliminate the compressible effects only with the small Mach number limit. Furthermore the source terms of the model are simple and contain no velocity gradients. Through the Chapman-Enskog expansion, the Macroscopic Equations for incompressible axisymmetric flows can be exactly recovered from the present LBGK model. Numerical simulations of the Hagen-Poiseuille flow, the pulsatile Womersley flow, the flow over a sphere, and the swirling flow in a closed cylindrical cavity are performed. The results agree well with the analytic solutions and the existing numerical or experimental data reported in some previous studies.
K H Luo - One of the best experts on this subject based on the ideXlab platform.
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three dimensional non orthogonal mrt pseudopotential lattice boltzmann model for multiphase flows
Computers & Fluids, 2019Co-Authors: Linlin Fei, K H LuoAbstract:Abstract In the classical multiple-relaxation-time (MRT) lattice Boltzmann (LB) method, the transformation matrix is formed by constructing a set of orthogonal basis vectors. In this paper, a theoretical and numerical study is performed to investigate the capability and efficiency of a non-orthogonal MRT-LB model for simulating multiphase flows. First, a three-dimensional non-orthogonal MRT-LB is proposed. A non-orthogonal MRT collision operator is devised based on a set of non-orthogonal basis vectors, through which the transformation matrix and its inverse matrix are considerably simplified as compared with those of an orthogonal MRT collision operator. Furthermore, through the Chapman-Enskog analysis, it is theoretically demonstrated that the three-dimensional non-orthogonal MRT-LB model can correctly recover the Macroscopic Equations at the Navier-Stokes level in the low Mach number limit. Numerical comparisons between the non-orthogonal MRT-LB model and the usual orthogonal MRT-LB model are made by simulating multiphase flows on the basis of the pseudopotential multiphase LB approach. The numerical results show that, in comparison with the usual orthogonal MRT-LB model, the non-orthogonal MRT-LB model can retain the numerical accuracy while simplifying the implementation.
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forcing scheme in pseudopotential lattice boltzmann model for multiphase flows
Physical Review E, 2012Co-Authors: K H LuoAbstract:The pseudopotential lattice Boltzmann (LB) model is a widely used multiphase model in the LB community. In this model, an interaction force, which is usually implemented via a forcing scheme, is employed to mimic the molecular interactions that cause phase segregation. The forcing scheme is therefore expected to play an important role in the pseudoepotential LB model. In this paper, we aim to address some key issues about forcing schemes in the pseudopotential LB model. First, theoretical and numerical analyses will be made for Shan-Chen's forcing scheme [Shan and Chen, Phys. Rev. E 47, 1815 (1993)] and the exact-difference-method forcing scheme [Kupershtokh et al., Comput. Math. Appl. 58, 965 (2009)]. The nature of these two schemes and their recovered Macroscopic Equations will be shown. Second, through a theoretical analysis, we will reveal the physics behind the phenomenon that different forcing schemes exhibit different performances in the pseudopotential LB model. Moreover, based on the analysis, we will present an improved forcing scheme and numerically demonstrate that the improved scheme can be treated as an alternative approach to achieving thermodynamic consistency in the pseudopotential LB model.
Zhenhua Chai - One of the best experts on this subject based on the ideXlab platform.
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lattice bgk model for incompressible axisymmetric flows
Communications in Computational Physics, 2012Co-Authors: Ting Zhang, Zhenhua Chai, Fumei RongAbstract:In this paper, a lattice Boltzmann BGK (LBGK) model is proposed for simulating incompressible axisymmetric flows. Unlike other existing axisymmetric lattice Boltzmann models, the present LBGK model can eliminate the compressible effects only with the small Mach number limit. Furthermore the source terms of the model are simple and contain no velocity gradients. Through the Chapman-Enskog expansion, the Macroscopic Equations for incompressible axisymmetric flows can be exactly recovered from the present LBGK model. Numerical simulations of the Hagen-Poiseuille flow, the pulsatile Womersley flow, the flow over a sphere, and the swirling flow in a closed cylindrical cavity are performed. The results agree well with the analytic solutions and the existing numerical or experimental data reported in some previous studies.
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lattice bgk model for incompressible axisymmetric flows
Communications in Computational Physics, 2012Co-Authors: Ting Zhang, Zhenhua Chai, Fumei RongAbstract:In this paper, a lattice Boltzmann BGK (LBGK) model is proposed for simulating incompressible axisymmetric flows. Unlike other existing axisymmetric lattice Boltzmann models, the present LBGK model can eliminate the compressible effects only with the small Mach number limit. Furthermore the source terms of the model are simple and contain no velocity gradients. Through the Chapman-Enskog expansion, the Macroscopic Equations for incompressible axisymmetric flows can be exactly recovered from the present LBGK model. Numerical simulations of the Hagen-Poiseuille flow, the pulsatile Womersley flow, the flow over a sphere, and the swirling flow in a closed cylindrical cavity are performed. The results agree well with the analytic solutions and the existing numerical or experimental data reported in some previous studies.
