Persistent memory of diffusing particles.
Persistent memory of diffusing particles.
复制标题
扩散粒子的持久记忆。
DOI：
10.1103/physreve.80.061134
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
P. Knabner
中科院分区：
文献类型：
--
作者：
N. Suciu;C. Vamos;F. Radu;H. Vereecken;P. Knabner
变系数对流扩散过程的方差被精确地分解为弥散项和由速度和初始位置之间的相关性组成的记忆项之和。对于随机初始条件，记忆项量化的偏离的前渐近方差的时间线性扩散行为。对于确定性的初始条件，记忆项考虑了扩散粒子的初始位置的记忆。基于全局随机游走算法的数值模拟表明，粒子云的初始分布的影响被认为是在数百个无量纲的时间。在有限相关范围的随机速度场中扩散的情况下，粒子在长时间限制内忘记初始位置，方差是自平均的，具有明显的正常扩散趋势。
The variance of the advection-diffusion processes with variable coefficients is exactly decomposed as a sum of dispersion terms and memory terms consisting of correlations between velocity and initial positions. For random initial conditions, the memory terms quantify the departure of the preasymptotic variance from the time-linear diffusive behavior. For deterministic initial conditions, the memory terms account for the memory of the initial positions of the diffusing particles. Numerical simulations based on a global random walk algorithm show that the influence of the initial distribution of the cloud of particles is felt over hundreds of dimensionless times. In case of diffusion in random velocity fields with finite correlation range the particles forget the initial positions in the long-time limit and the variance is self-averaging, with clear tendency toward normal diffusion.