论文标题
部分可观测时空混沌系统的无模型预测
Computing hydrodynamic interactions in confined doubly-periodic geometries in linear time
论文作者
论文摘要
我们开发了力耦合方法的线性缩放变体[K.。 Yeo和M. R. Maxey,J。FluidMech。 649,205-231(2010)]用于计算限制在双底壁或两个壁(缝隙通道)的颗粒之间的流体动力相互作用。我们的频谱准确的Stokes求解器在周期性的$ xy $ plane中使用快速傅立叶变换(FFT),而chebyshev pyenmials则在墙壁正常的差异$ z $方向上使用。我们将问题分解为两个问题。首先是在存在$ z $方向上具有自由空间边界条件的颗粒(源项)的双层二次子问题中,我们通过从最近的方法中借用一种想法来快速评估对双层静态几何形状中的静电相互作用的快速评估[O。 Maxian,R。P。Peláez,L。Greengard和A. Donev,J。Chem。物理。 154,204107(2021)]。第二个是校正子问题,将边界条件强加于墙壁。而不是传统的高斯内核,而是使用半圆内核的指数来对源术语(身体力)进行建模,并为粒子的存在提供,并为核参数提供最佳值,以确保给定的流体动力半径至少具有至少两位精度,旋转和旋转和转换率。在图形处理单元中实现的求解器的计算时间与粒子数量线性缩放,并允许对胶体微胶卷的沉积层的计算在不到一秒钟的时间内使用约一百万个粒子。我们发现,在一个狭缝通道中,微胶卷的驱动密集悬架保持与单个壁上相同的两层结构,但由于限制的增加而以较低的集体速度移动。
We develop a linearly-scaling variant of the Force Coupling Method [K. Yeo and M. R. Maxey, J. Fluid Mech. 649, 205-231 (2010)] for computing hydrodynamic interactions among particles confined to a doubly-periodic geometry with either a single bottom wall or two walls (slit channel) in the aperiodic direction. Our spectrally-accurate Stokes solver uses the Fast Fourier Transform (FFT) in the periodic $xy$ plane and Chebyshev polynomials in the aperiodic $z$ direction normal to the wall(s). We decompose the problem into two problems. The first is a doubly-periodic subproblem in the presence of particles (source terms) with free-space boundary conditions in the $z$ direction, which we solve by borrowing ideas from a recent method for rapid evaluation of electrostatic interactions in doubly-periodic geometries [O. Maxian, R. P. Peláez, L. Greengard and A. Donev, J. Chem. Phys. 154, 204107 (2021)]. The second is a correction subproblem to impose the boundary conditions on the wall(s). Instead of the traditional Gaussian kernel, we use the exponential of a semicircle kernel to model the source terms (body force) due to the presence of particles, and provide optimum values for the kernel parameters that ensure a given hydrodynamic radius with at least two digits of accuracy and rotational and translational invariance. The computation time of our solver, which is implemented in graphical processing units, scales linearly with the number of particles, and allows computations with about a million particles in less than a second for a sedimented layer of colloidal microrollers. We find that in a slit channel, a driven dense suspension of microrollers maintains the same two-layer structure as above a single wall, but moves at a substantially lower collective speed due to increased confinement.