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The unified gas-kinetic scheme (UGKS) provides a framework for simulating multiscale transport with the updates of both gas distribution function and macroscopic flow variables on the cell size and time step scales. The multiscale dynamics…

Numerical Analysis · Mathematics 2018-11-20 Chang Liu , Yajun Zhu , Kun Xu

The development of radiation hydrodynamical methods that are able to follow gas dynamics and radiative transfer self-consistently is key to the solution of many problems in numerical astrophysics. Such fluid flows are highly complex, rarely…

Two kinetic models are proposed for high-temperature rarefied (or non-equilibrium) gas flows with radiation. One of the models uses the Boltzmann collision operator to model the translational motion of gas molecules, which has the ability…

Fluid Dynamics · Physics 2023-06-28 Qi Li , Jianan Zeng , Lei Wu

The set of benchmark solutions used in the thermal radiative transfer community suffer some coverage gaps, in particular nonlinear, non-equilibrium problems. Also, there are no non-equilibrium, optically thick benchmarks. These shortcomings…

Computational Engineering, Finance, and Science · Computer Science 2023-05-10 William Bennett , Ryan G. McClarren

In this paper, a unified algorithm will be proposed for the study of gas-solid particle multiphase flow. The gas-kinetic scheme (GKS) is used to simulate the continuum gas phase and the multiscale unified gas-kinetic wave-particle (UGKWP)…

Computational Physics · Physics 2023-04-10 Xiaojian Yang , Wei Shyy , Kun Xu

We investigate the kinetic theory of two-temperature plasmas for reactive polyatomic gas mixtures. The Knudsen number is taken proportional to the square root of the mass ratio between electrons and heavy-species, and thermal…

Plasma Physics · Physics 2019-02-05 Jean-Maxime Orlac'H , Vincent Giovangigli , Tatiana Novikova , Pere Roca

In this paper, a compact high-order gas-kinetic scheme (GKS) with spectral resolution will be presented and used in the simulation of acoustic and shock waves. For accurate simulation, the numerical scheme is required to have excellent…

Computational Physics · Physics 2020-12-30 Fengxiang Zhao , Xing Ji , Wei Shyy , Kun Xu

To determine the electron heat flux density on macroscopic scales, the most widely used approach is to solve a diffusion equation through a multi-group technique. This method is however restricted to transport induced by temperature…

Radiation hydrodynamics describes the interaction between high-temperature hypersonic plasmas and the radiation they emit or absorb, a coupling that plays a central role in many astrophysical phenomena related to accretion and ejection…

Plasma Physics · Physics 2026-01-13 Gonzague Radureau

From a mathematical perspective, radiation hydrodynamics can be thought of as a system of hyperbolic balance laws with dual multiscale behavior (multiscale behavior associated with the hyperbolic wave speeds as well as multiscale behavior…

Computational Physics · Physics 2015-05-19 Michael D Sekora , James M Stone

We describe an approach for incorporating radiative transfer into 3D hydrodynamic cosmological simulations. The method, while approximate, allows for a self-consistent treatment of self-shielding and shadowing, diffuse and point sources of…

Astrophysics · Physics 2007-05-23 Michael L. Norman , Paschalis Paschos , Tom Abel

Simulating multiscale flows with moving boundaries, such as hypersonic multi-body separation and flows in micro-electro-mechanical systems (MEMS), requires robust numerical methods that couple mesh deformation with complex flow physics.…

Fluid Dynamics · Physics 2026-04-14 Yue Zhang , Wenpei Long , Junzhe Cao , Kun Xu

For increasingly rarefied flowfields, the Navier-Stokes (NS) equations lose accuracy partially due to the single temperature approximation. To overcome this barrier, a continuum multi-temperature model based on the Bhatnagar-Gross-Krook…

Fluid Dynamics · Physics 2018-10-12 Guiyu Cao , Hualin Liu , Kun Xu

We describe RAGE, the ``Radiation Adaptive Grid Eulerian'' radiation-hydrodynamics code, including its data structures, its parallelization strategy and performance, its hydrodynamic algorithm(s), its (gray) radiation diffusion algorithm,…

The unified gas-kinetic wave-particle (UGKWP) method is a hybrid method for multiscale flow simulations, in which the contributions to the whole gas evolution from deterministic hydrodynamic wave and stochastic particle transport are…

Computational Physics · Physics 2024-08-16 Zhaoli Guo , Yajun Zhu , Kun Xu

We have developed an economical, effective numerical scheme for cosmic-ray transport suitable for treatment of electrons up to a few hundreds of GeV in multidimensional simulations of radio galaxies. The method follows the electron…

Astrophysics · Physics 2009-10-31 T. W. Jones , I. L. Tregillis , Dongsu Ryu

In this paper, the unified gas-kinetic wave-particle (UGKWP) method is further developed for diatomic gas with the energy exchange between translational and rotational modes for flow study in all regimes. The multiscale transport mechanism…

Computational Physics · Physics 2021-07-07 Xiaocong Xu , Yipei Chen , Chang Liu , Zhihui Li , Kun Xu

In this paper, a class of compact higher-order gas-kinetic schemes (GKS) with spectral resolution will be presented. Based on the high-order gas evolution model in GKS, both the interface flux function and conservative flow variables can be…

Computational Physics · Physics 2019-01-03 Fengxiang Zhao , Xing Ji , Wei Shyy , Kun Xu

The unified gas kinetic scheme (UGKS) is a direct modeling method based on the gas dynamical model on the mesh size and time step scales. With the implementation of particle transport and collision in a time-dependent flux function, the…

Computational Physics · Physics 2017-10-25 Yajun Zhu , Chengwen Zhong , Kun Xu

We explore the application of Monte Carlo transport methods to solving coupled radiation-hydrodynamics problems. We use a time-dependent, frequency-dependent, 3-dimensional radiation transport code, that is special relativistic and includes…

Instrumentation and Methods for Astrophysics · Physics 2015-06-19 Nathaniel Roth , Daniel Kasen