The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Chengwen Zhong - One of the best experts on this subject based on the ideXlab platform.
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a conservative Implicit Scheme for steady state solutions of diatomic gas flow in all flow regimes
Computer Physics Communications, 2020Co-Authors: Ruifeng Yuan, Chengwen ZhongAbstract:Abstract An Implicit Scheme for steady state solutions of diatomic gas flow is presented. The Rykov model equation is solved in the finite volume discrete velocity method framework, in which the translational and rotational degrees of freedom are taken into account. At the cell interface, a difference Scheme of the model equation is used to construct a multiscale flux (similar to discrete unified gas-kinetic Scheme), so that the cell size is not constrained by the cell Knudsen number. The physical local time step is implemented to preserve the multiscale property in the nonuniform-mesh case. The Implicit macroscopic prediction technique is adopted to find a predicted equilibrium state at each time step, making the Scheme highly efficient in all flow regimes. Furthermore, an integral error compensation technique with negligible computational cost is proposed, which makes the Scheme conservative and allows more flexible discretization for particle velocity space. With the compensation technique, the unstructured velocity-space mesh is used in the test cases, which reduces the velocity mesh number significantly. The present method is proved to be efficient and accurate.
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a conservative Implicit Scheme for steady state solutions of diatomic gas flow in all flow regimes
arXiv: Computational Physics, 2018Co-Authors: Ruifeng Yuan, Chengwen ZhongAbstract:An Implicit Scheme for steady state solutions of diatomic gas flow is presented. The method solves the Rykov model equation in the finite volume discrete velocity method (DVM) framework, in which the translational and rotational degrees of freedom are taken into account. At the cell interface, a difference Scheme of the model equation is used to construct a multiscale flux (similar to discrete unified gas-kinetic Scheme (DUGKS)), so that the cell size is not constrained by the cell Knudsen (Kn) number. The physical local time step is implemented to preserve the multiscale property in the nonuniform-mesh case. The Implicit macroscopic prediction technique is adopted to find a predicted equilibrium state at each time level and the Implicit macroscopic governing equation is solved along with the Implicit microscopic system. Furthermore, an efficient integral error compensation technique is applied, which makes the Scheme conservative and allows more flexible discretization for particle velocity space. In the test cases, the unstructured velocity-space mesh is used, the present method is proved to be efficient and accurate.
Ruifeng Yuan - One of the best experts on this subject based on the ideXlab platform.
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a conservative Implicit Scheme for steady state solutions of diatomic gas flow in all flow regimes
Computer Physics Communications, 2020Co-Authors: Ruifeng Yuan, Chengwen ZhongAbstract:Abstract An Implicit Scheme for steady state solutions of diatomic gas flow is presented. The Rykov model equation is solved in the finite volume discrete velocity method framework, in which the translational and rotational degrees of freedom are taken into account. At the cell interface, a difference Scheme of the model equation is used to construct a multiscale flux (similar to discrete unified gas-kinetic Scheme), so that the cell size is not constrained by the cell Knudsen number. The physical local time step is implemented to preserve the multiscale property in the nonuniform-mesh case. The Implicit macroscopic prediction technique is adopted to find a predicted equilibrium state at each time step, making the Scheme highly efficient in all flow regimes. Furthermore, an integral error compensation technique with negligible computational cost is proposed, which makes the Scheme conservative and allows more flexible discretization for particle velocity space. With the compensation technique, the unstructured velocity-space mesh is used in the test cases, which reduces the velocity mesh number significantly. The present method is proved to be efficient and accurate.
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a conservative Implicit Scheme for steady state solutions of diatomic gas flow in all flow regimes
arXiv: Computational Physics, 2018Co-Authors: Ruifeng Yuan, Chengwen ZhongAbstract:An Implicit Scheme for steady state solutions of diatomic gas flow is presented. The method solves the Rykov model equation in the finite volume discrete velocity method (DVM) framework, in which the translational and rotational degrees of freedom are taken into account. At the cell interface, a difference Scheme of the model equation is used to construct a multiscale flux (similar to discrete unified gas-kinetic Scheme (DUGKS)), so that the cell size is not constrained by the cell Knudsen (Kn) number. The physical local time step is implemented to preserve the multiscale property in the nonuniform-mesh case. The Implicit macroscopic prediction technique is adopted to find a predicted equilibrium state at each time level and the Implicit macroscopic governing equation is solved along with the Implicit microscopic system. Furthermore, an efficient integral error compensation technique is applied, which makes the Scheme conservative and allows more flexible discretization for particle velocity space. In the test cases, the unstructured velocity-space mesh is used, the present method is proved to be efficient and accurate.
Caterina Cocchi - One of the best experts on this subject based on the ideXlab platform.
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layerpcm an Implicit Scheme for dielectric screening from layered substrates
Journal of Chemical Physics, 2021Co-Authors: Jannis Krumland, Gabriel Gil, Stefano Corni, Caterina CocchiAbstract:We present LayerPCM, an extension of the polarizable-continuum model coupled to real-time time-dependent density-functional theory, for an efficient and accurate description of the electrostatic interactions between molecules and multilayered dielectric substrates on which they are physisorbed. The former are modeled quantum-mechanically, while the latter are treated as polarizable continua characterized by their dielectric constants. The proposed approach is purposely designed to simulate complex hybrid heterostructures with nano-engineered substrates including a stack of anisotropic layers. LayerPCM is suitable for describing the polarization-induced renormalization of frontier energy levels of the adsorbates in the static regime. Moreover, it can be reliably applied to simulating laser-induced ultrafast dynamics of molecules through the inclusion of electric fields generated by Fresnel-reflection at the substrate. Depending on the complexity of the underlying layer structure, such reflected fields can assume non-trivial shapes and profoundly affect the dynamics of the photo-excited charge carriers in the molecule. In particular, the interaction with the substrate can give rise to strong delayed fields, which lead to interference effects resembling those of multi-pulse-based spectroscopy. The robustness of the implementation and the above-mentioned features are demonstrated with a number of examples, ranging from intuitive models to realistic systems.
Luc Mieussens - One of the best experts on this subject based on the ideXlab platform.
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discrete velocity model and Implicit Scheme for the bgk equation of rarefied gas dynamics
Mathematical Models and Methods in Applied Sciences, 2000Co-Authors: Luc MieussensAbstract:We present a numerical method for computing transitional flows as described by the BGK equation of gas kinetic theory. Using the minimum entropy principle to define a discrete equilibrium function, a discrete velocity model of this equation is proposed. This model, like the continuous one, ensures positivity of solutions, conservation of moments, and dissipation of entropy. The discrete velocity model is then discretized in space and time by an explicit finite volume Scheme which is proved to satisfy the previous properties. A linearized Implicit Scheme is then derived to efficiently compute steady-states; this method is then verified with several test cases.
Kenneth G Powell - One of the best experts on this subject based on the ideXlab platform.
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a parallel explicit Implicit time stepping Scheme on block adaptive grids
Journal of Computational Physics, 2006Co-Authors: G Toth, Darren L De Zeeuw, T I Gombosi, Kenneth G PowellAbstract:We present a parallel explicit/Implicit time integration Scheme well suited for block-adaptive grids. The basic idea of the algorithm is that the time stepping Scheme can differ in the blocks of the grid for a given time step: an explicit Scheme is used in the blocks where the local stability requirement is not violated and an Implicit Scheme is used in the blocks where the explicit Scheme would be unstable. The Implicit Scheme is second order in time. The non-linear system of equations is linearized with Newton linearization. The linear system is solved with a preconditioned Krylov subspace iterative Scheme. The Schwarz type preconditioning is also based on the block structure of the grid. We discuss load balancing for parallel execution and the optimal choice of the time step for speed and robustness. The parallel efficiency of the Scheme is demonstrated for the equations of magnetohydrodynamics with a geophysics application in three dimensions. The control of the numerical divergence of the magnetic field in combination with the explicit/Implicit time stepping Scheme is also discussed.
