A hybrid molecular-continuum method for unsteady compressible multiscale flows
A hybrid molecular-continuum method for unsteady compressible multiscale flows
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DOI：
10.1017/jfm.2015.83
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发表时间：
2015-04-01
影响因子：
3.7
通讯作者：
Reese, Jason M.
中科院分区：
文献类型：
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作者：
Borg, Matthew K.;Lockerby, Duncan A.;Reese, Jason M.
我们提出了一种内流多尺度方法（“非稳态 IMM”），用于解决纳米约束高纵横比几何形状中的可压缩、时变/非稳态流动问题。 IMM 是一种混合分子连续体方法，可在宏观尺度上提供准确的流动预测，因为对连续体流体公式的局部微观校正是通过空间和时间分布的分子模拟生成的。利用时间和长度尺度上的分离可以节省数量级的计算量，远远大于其他混合方法。我们将非稳态 IMM 应用于具有各种时间和长度尺度分离的会聚-发散通道流问题。尽可能与完整的分子模拟进行比较；在大多数情况下，混合解决方案的准确性非常好。我们证明了解决方案对宏观-微观时间步长的准确性的敏感性，以及完整分子模拟的计算加速，取决于问题中存在的尺度分离程度。对于本文考虑的最大通道长度，与理论上的全分子模拟相比，获得了六个数量级的加速。
We present an internal-flow multiscale method ('unsteady-IMM') for compressible, time-varying/unsteady flow problems in nano-confined high-aspect-ratio geometries. The IMM is a hybrid molecular-continuum method that provides accurate flow predictions at macroscopic scales because local microscopic corrections to the continuum-fluid formulation are generated by spatially and temporally distributed molecular simulations. Exploiting separation in both time and length scales enables orders of magnitude computational savings, far greater than seen in other hybrid methods. We apply the unsteady-IMM to a converging-diverging channel flow problem with various time-and length-scale separations. Comparisons are made with a full molecular simulation wherever possible; the level of accuracy of the hybrid solution is excellent in most cases. We demonstrate that the sensitivity of the accuracy of a solution to the macro-micro time-stepping, as well as the computational speed-up over a full molecular simulation, is dependent on the degree of scale separation that exists in a problem. For the largest channel lengths considered in this paper, a speed-up of six orders of magnitude has been obtained, compared with a notional full molecular simulation.