论文标题

粒度硬粒玻尔兹曼方程的流体动态极限 - 几乎弹性状态

Fluid dynamic limit of Boltzmann equation for granular hard--spheres in a nearly elastic regime

论文作者

Alonso, Ricardo J., Lods, Bertrand, Tristani, Isabelle

论文摘要

在本文中,我们提供了从玻尔兹曼方程的第一个严格衍生物,用于具有较小非弹性的非弹性硬球。我们获得的流体动力系统是一种不可压缩的Navier-Stokes-toursy系统,具有自一致的强迫术语,因此是第一个正确描述快速颗粒流量的流体动力系统。为此,我们以无量纲的形式编写了玻尔兹曼方程,引入了无量纲的诺德森数字,该数字旨在倾向于0。当时的困难是很多,第一个来自原始的Boltzmann方程是自由冷却的事实,因此,自由冷却,因此需要与一个平稳的变量进行自我衡量的变量,以实现一个平稳的居住状态。后者不是显式的,并且是重尾,这是适应能量估计和光谱分析的主要障碍。这里的主要挑战之一是了解恢复系数(量化微观水平上的能量损失)与诺德森数之间的关系。完成此操作以识别正确的几乎弹性状态以捕获非平凡的流体动力行为。然后,我们能够在接近均衡状态下重新定制的玻尔兹曼方程的固定溶液的纳德森溶液统一证明指数稳定性。最后,我们证明,我们对Boltzmann方程的解决方案以某些非常特定的弱感觉收敛到某些仅通过宏观数量来取决于时间和空间变量的流体动力解。这样的宏观数量是解决不可压缩的Navier-Stokes-foury系统的解决方案,在这种情况下似乎是新的。

In this paper, we provide the first rigorous derivation of hydrodynamic equations from the Boltzmann equation for inelastic hard spheres with small inelasticity. The hydrodynamic system that we obtain is an incompressible Navier-Stokes-Fourier system with self-consistent forcing terms and is thus the first hydrodynamic system that properly describes rapid granular flows. To do that, we write our Boltzmann equation in nondimensional form introducing the dimensionless Knudsen number which is intended to tend to 0. The difficulties are then manyfold, the first one coming from the fact that the original Boltzmann equation is free-cooling and thus requires a self-similar change of variables to work with an equation that has an homogeneous steady state. The latter is not explicit and is heavy-tailed, which is a major obstacle to adapt energy estimates and spectral analysis. One of the main challenges here is to understand the relation between the restitution coefficient (which quantifies the loss of energy at the microscopic level) and the Knudsen number. This is done identifying the correct nearly elastic regime to capture nontrivial hydrodynamic behavior. We are then able to prove exponential stability uniformly with respect to the Knudsen number of the solution of our rescaled Boltzmann equation in a close to equilibrium regime. Finally, we prove that our solution to the Boltzmann equation converges in some very specific weak sense towards some hydrodynamic solution which depends on time and space variables only through macroscopic quantities. Such macroscopic quantities are solutions to a suitable modification of the incompressible Navier-Stokes-Fourier system which appears to be new in this context.

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