ITR/AP (CHE): Mutliscale Treatment of Fluid-Solid Interfaces: Development of Hybrid Monte Carlo and Finite Element Code

0112929这个ITR/AP小团体奖支持开发高效和健壮的计算方法，用于模拟涉及截然不同长度尺度的现象的物理系统。其结果将服务于计算机辅助设计、分析和建模的重要需要。一个经典的例子是一个系统，它涉及从分子到宏观尺度上具有复杂几何形状的流固界面。一方面，基于连续介质近似的计算建模方法(如有限元和有限差分技术)只能描述比界面上流体密度显著变化的典型距离长得多的波长处的力学响应。另一方面，整个系统太大了，不能用一个完全原子化的模拟来处理，这个模拟将同时涵盖所有尺度的反应。为了解决这个问题，将采用蒙特卡罗-有限元混合格式，其中界面上的流体分子被显式处理，而固体被连续介质技术处理。其中的随机变量由流体分子的位置和覆盖固相的有限元网格的节点组成。蒙特卡罗的随机性使其适合于一种高效的并行计算方案，这对于模拟真实世界的系统至关重要。一个跨学科的团队已经组成了一个为期三年的项目，其预期的结果是一个强大的计算方案，用于分析现实流体-固体系统的热力响应，其中分子非均质界面与宏观连续介质的耦合在其中起着至关重要的作用。

0112929ZhengThis ITR/AP Small Group Award supports development of efficient and robust computational methods for simulating physical systems involving phenomena at drastically different length scales. The results will serve an important need in computer-aided design, analysis andmodeling. A classic example is a system that involves fluid-solid interfaces with complex geometries on scales ranging from molecular to macroscopic. On one hand, computational modeling approaches based on continuum approximations (e.g., finite-element and finite-difference techniques) are capable of describing mechanical responses only at wavelengths much longer than the typical distances over which the fluid density at interfaces varies appreciably. On the other hand, the whole system is far too large to be treated by a fully atomistic simulation that would encompass responses at all scales simultaneously. To address this problem a hybrid Monte Carlo-finite element scheme, in which fluid molecules at the interface are treated explicitly, while the solid is handled by continuum techniques, will be applied. A "reduced" description in which the stochastic variables consist of the positions of thefluid molecules and the nodes of the finite-element mesh covering the solid phase will be developed. The stochastic nature of Monte Carlo lends itself to an efficient parallel computing scheme, which is crucial for simulating real-world systems. A multi-disciplinary team has been assembled to undertake the three-year project, the expected outcome of which is a powerful computational scheme for analyzing the thermomechanical response of realistic fluid-solid systems in which the coupling of the molecularly heterogeneous interfaces to the macroscopic continuum plays an essential role.***