论文标题
具有平滑颗粒流体动力学的全球时间可逆流体模拟
Globally time-reversible fluid simulations with smoothed particle hydrodynamics
论文作者
论文摘要
本文介绍了弱压缩平滑粒子流体动力学（SPH）的能量保存和全球时间可逆的代码。我们不会在普通微分方程级别上为Monaghan的原始SPH方案添加任何其他动力学，但是我们通过使用校正的表达式进行密度并调用符号积分器来显示如何离散方程。此外，要实现全球及时可逆性，我们必须纠正初始状态，实现保守的流体壁相互作用并使用固定点算术。尽管数值方案在全球范围内是可逆的（在恢复初始条件的同时可以向后溶解），但我们观察到粒子速度的热化和玻尔兹曼熵的生长。换句话说，当我们看不到所有可能的细节时，如仅取决于一个粒子分布函数的玻尔兹曼熵中时，我们会观察到纯粹可逆动力学的热力学（不可逆行为）的第二定律的出现。
This paper describes an energy-preserving and globally time-reversible code for weakly compressible smoothed particle hydrodynamics (SPH). We do not add any additional dynamics to the Monaghan's original SPH scheme at the level of ordinary differential equation, but we show how to discretize the equations by using a corrected expression for density and by invoking a symplectic integrator. Moreover, to achieve the global-in-time reversibility, we have to correct the initial state, implement a conservative fluid-wall interaction, and use the fixed-point arithmetic. Although the numerical scheme is reversible globally in time (solvable backwards in time while recovering the initial conditions), we observe thermalization of the particle velocities and growth of the Boltzmann entropy. In other words, when we do not see all the possible details, as in the Boltzmann entropy, which depends only on the one-particle distribution function, we observe the emergence of the second law of thermodynamics (irreversible behavior) from purely reversible dynamics.
