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arXiv 0910.3968cond-mat.softcond-mat.mes-hall
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复杂流体动力学的粒子-连续介质混合方法

A hybrid particle-continuum method for hydrodynamics of complex fluids

A. Donev, J. B. Bell, A. L. Garcia, B. J. Alder

摘要:

一个先前发展的混合粒子-连续介质方法[J. B.贝尔,A.加西亚和S. A. Williams,SIAM Multiscale Modeling and Simulation,6:1256-1280,2008]被推广到稠密流体以及二维和三维流动。该格式将显式脉动可压缩Navier-Stokes解与各向同性直接模拟蒙特卡罗(DSMC)粒子方法耦合在一起[A。Donev和A. L. Garcia和B. J. Alder,ArXiv预印本0908.0510]。为了实现粒子(微观尺度)和连续体(宏观尺度)区域之间的双向动态耦合,连续体求解器为粒子子域提供基于状态的边界条件,而粒子求解器为连续体子域提供基于通量的边界条件。平衡扩散(布朗)运动的一个大的球形珠悬浮在颗粒流体中检查,表明混合方法正确地再现珠的速度自相关函数,但只有当热波动包括在连续求解器。最后,混合被施加到著名的绝热活塞问题,它被发现,混合正确地再现缓慢的非平衡松弛的活塞向热力学平衡,但再次,只有连续求解器包括随机(白噪声)通量项。这些例子清楚地表明,需要包括在混合多尺度方法中采用的连续求解器的波动。

英文摘要:

A previously-developed hybrid particle-continuum method [J. B. Bell, A. Garcia and S. A. Williams, SIAM Multiscale Modeling and Simulation, 6:1256-1280, 2008] is generalized to dense fluids and two and three dimensional flows. The scheme couples an explicit fluctuating compressible Navier-Stokes solver with the Isotropic Direct Simulation Monte Carlo (DSMC) particle method [A. Donev and A. L. Garcia and B. J. Alder, ArXiv preprint 0908.0510]. To achieve bidirectional dynamic coupling between the particle (microscale) and continuum (macroscale) regions, the continuum solver provides state-based boundary conditions to the particle subdomain, while the particle solver provides flux-based boundary conditions for the continuum subdomain. The equilibrium diffusive (Brownian) motion of a large spherical bead suspended in a particle fluid is examined, demonstrating that the hybrid method correctly reproduces the velocity autocorrelation function of the bead but only if thermal fluctuations are included in the continuum solver. Finally, the hybrid is applied to the well-known adiabatic piston problem and it is found that the hybrid correctly reproduces the slow non-equilibrium relaxation of the piston toward thermodynamic equilibrium but, again, only the continuum solver includes stochastic (white-noise) flux terms. These examples clearly demonstrate the need to include fluctuations in continuum solvers employed in hybrid multiscale methods.

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