Multiscale gas flows appear in many fields and have received particular attention in recent years. It is challenging to model and simulate such processes due to the large span of temporal and spatial scales. The discrete unified gas kinetic scheme (DUGKS) is a recently developed numerical approach for simulating multiscale flows based on kinetic models. The finite-volume DUGKS differs from the classical kinetic methods in the modeling of gas evolution and the reconstruction of interface flux. Particularly, the distribution function at a cell interface is reconstructed from the characteristic solution of the kinetic equation in space and time, such that the particle transport and collision effects are coupled, accumulated, and evaluated in a numerical time step scale. Consequently, the cell size and time step of DUGKS are not passively limited by the particle mean-free-path and relaxation time. As a result, the DUGKS can capture the flow behaviors in all regimes without resolving the kinetic scale. Particularly, with the variation of the ratio between numerical mesh size scale and kinetic mean free path scale, the DUGKS can serve as a self-adaptive multiscale method. The DUGKS has been successfully applied to a number of flow problems with multiple flow regimes. This paper presents a brief review of the progress of this method.

中文翻译：

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多尺度流离散统一气体动力学方案的研究进展

多尺度气流出现在许多领域，并且近年来受到了特别的关注。由于时间和空间尺度的跨度较大，因此对此类过程进行建模和仿真具有挑战性。离散统一气体动力学方案（DUGKS）是最近开发的用于基于动力学模型模拟多尺度流量的数值方法。有限体积的DUGKS在气体逸出的建模和界面通量的重建方面不同于经典的动力学方法。特别地，根据动力学方程在空间和时间上的特征解重建单元界面处的分布函数，从而以数字时间步长尺度耦合，累积和评估粒子传输和碰撞效果。所以，DUGKS的细胞大小和时间步长不受粒子平均自由程和弛豫时间的被动限制。结果，DUKGS可以捕获所有状态下的流动行为，而无需解决动力学规模。特别地，随着数值网格尺寸尺度和动力学平均自由程尺度之间的比率的变化，DUGGS可以用作自适应多尺度方法。DUGKS已成功应用于具有多种流动状态的许多流动问题。本文简要介绍了该方法的进展。DUGKS可以用作自适应多尺度方法。DUGKS已成功应用于具有多种流动状态的许多流动问题。本文简要介绍了该方法的进展。DUGKS可以用作自适应多尺度方法。DUGKS已成功应用于具有多种流动状态的许多流动问题。本文简要介绍了该方法的进展。