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Related papers: Adaptive wave-particle decomposition in UGKWP meth…

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Multiscale non-equilibrium physics at large variations of local Knudsen number are encountered in applications of aerospace engineering and micro-electro-mechanical systems, such as high-speed flying vehicles and low pressure of the…

Fluid Dynamics · Physics 2023-12-06 Yufeng Wei , Wenpei Long , Kun Xu

The unified gas-kinetic wave-particle method (UGKWP) has been developed for the multiscale gas, plasma, and multiphase flow transport processes for the past years. In this work, we propose an implicit unified gas-kinetic wave-particle…

Computational Physics · Physics 2023-09-22 Chang Liu , Weiming Li , Peng Song , Kun Xu

Over the past 7 decades, the classical Monte Carlo method has played a huge role in the fields of rarefied gas flow and micro/nano scale heat transfer, but it also has shortcomings: the time step and cell size are limited by the relaxation…

Computational Physics · Physics 2025-05-15 Hongyu Liu , Xiaojian Yang , Chuang Zhang , Xing Ji , Kun Xu

This paper presents a highly efficient implicit unified gas-kinetic particle (IUGKP) method for obtaining steady-state solutions of multi-scale phonon transport. The method adapts and reinterprets the integral solution of the BGK equation…

Computational Physics · Physics 2025-06-12 Hongyu Liu , Xiaojian Yang , Chuang Zhang , Xing Ji , Kun Xu

In this paper, a unified gas kinetic scheme with adaptive velocity space (AUGKS) for multiscale flow transport will be developed. In near-equilibrium flow regions, particle distribution function is close to the Chapman-Enskog expansion and…

Computational Physics · Physics 2018-02-15 Tianbai Xiao , Kun Xu , Qingdong Cai

The unified gas-kinetic scheme (UGKS) is a direct modeling method for multiple scale transports. The modeling scale of the scheme is the mesh size and time step, and the ratios of the mesh size over particle mean free path or the time step…

Computational Physics · Physics 2019-05-01 Yajun Zhu , Chengwen Zhong , Kun Xu

The Unified Gas-Kinetic Wave-Particle (UGKWP) method, developed for multiscale simulation of partially ionized plasmas, has been extended to unstructured meshes, enabling the modeling of electromagnetic flows around a hemisphere across…

Plasma Physics · Physics 2026-04-29 Zhigang Pu , Kun Xu

The gas dynamics under gravitational field is usually associated with the multiple scale nature due to large density variation and a wide range of local Knudsen number. It is chal- lenging to construct a reliable numerical algorithm to…

Computational Physics · Physics 2017-02-01 Tianbai Xiao , Qingdong Cai , Kun Xu

This paper proposes a unified gas-kinetic particle (UGKP) method for the frequency-dependent photon transport process. The photon transport is a typical multiscale process governed by the nonlinear radiative transfer equations (RTE). The…

Numerical Analysis · Mathematics 2023-01-18 Weiming Li , Chang Liu , Peng Song

This paper is a continuation of our earlier work [Z.L. Guo {\it et al.}, Phys. Rev. E {\bf 88}, 033305 (2013)] where a multiscale numerical scheme based on kinetic model was developed for low speed isothermal flows with arbitrary Knudsen…

Fluid Dynamics · Physics 2015-06-22 Zhaoli Guo , Ruijie Wang , Kun Xu

In this paper, we extend the unified kinetic particle (UGKP) method to the frequency-dependent radiative transfer equation with both absorption-emission and scattering processes. The extended UGKP method could not only capture the diffusion…

Computational Physics · Physics 2023-02-17 Yuan Hu , Chang Liu

The flow regime of micro flow varies from collisionless regime to hydrodynamic regime according to the Knudsen number. On the kinetic scale, the dynamics of micro flow can be described by the linearized kinetic equation. In the continuum…

Computational Physics · Physics 2020-05-27 Chang Liu , Kun Xu

This study extends the Unified Gas-Kinetic Scheme (UGKS) and the Unified Gas-Kinetic Wave-Particle (UGKWP) method for electrostatic plasma modeling, ensuring the correct asymptotic limits with respect to both the Debye length and the mean…

Computational Physics · Physics 2025-12-18 Zhigang Pu , Kun Xu

The hypersonic flow around near-space vehicles constitutes a multi-scale flow problem. Due to insufficient molecular collisions to achieve equilibrium, rarefied gas effects are present in the flow field. Thus, numerical methods capable of…

Fluid Dynamics · Physics 2025-07-02 Sirui Yang , Chengwen Zhong , Ningchao Ding , Junzhe Cao , He Zhang , Congshan Zhuo , Sha Liu

In this work, the Navier-Stokes (NS) solver is combined with the Direct simulation Monte Carlo (DSMC) solver in a direct way, under the wave-particle formulation [J. Comput. Phys. 401, 108977 (2020)]. Different from the classical domain…

Computational Physics · Physics 2023-09-26 Junzhe Cao , Sha Liu , Sirui Yang , Chengwen Zhong

A Quantified Model-Competition (QMC) mechanism for multi-scale flows is extracted from the integral (analytical) solution of the Boltzmann-BGK model equation. In the QMC mechanism, the weight of the rarefied model and the weight of the…

Computational Physics · Physics 2020-07-15 Sha Liu , Chengwen Zhong , Ming Fang

A unified gas kinetic scheme (UGKS) for multi-scale and multi-component plasma transport is constructed. The current scheme is a direct modeling method, where the time evolution solutions from the Vlasov-BGK equations of electron and ion…

Computational Physics · Physics 2017-12-21 Chang Liu , Kun Xu

Fluid dynamic equations are valid in their respective modeling scales. With a variation of the modeling scales, theoretically there should have a continuous spectrum of fluid dynamic equations. In order to study multiscale flow evolution…

Numerical Analysis · Mathematics 2017-12-21 Chang Liu , Kun Xu , Quanhua Sun , Qingdong Cai

In this paper, a unified gas kinetic scheme for multiphase dilute gas-particle system is proposed. The UGKS multiphase (UGKS-M) is a finite volume method, which captures flow physics in the regimes from collisionless multispecies transport…

Computational Physics · Physics 2019-05-01 Chang Liu , Zhao Wang , Kun Xu

In this paper, a unified gas-kinetic scheme (UGKS) with simplified multi-scale numerical flux is proposed for the thermodynamic non-equilibrium flow simulation involving the excitation of molecular vibrational degrees of freedom in all flow…

Fluid Dynamics · Physics 2023-02-08 Rui Zhang , Sha Liu , Chengwen Zhong , Congshan Zhuo