一种表征水力糙率的快速直接数值模拟方法
A fast direct numerical simulation method for characterising hydraulic roughness
摘要：
我们描述了一种快速的直接数值模拟（DNS）方法，承诺直接计算任何给定的粗糙表面的水力粗糙度，从水力光滑到完全粗糙的制度。该方法通过采用最小跨度通道（Jimenez & Moin 1991）避免了与模拟高雷诺数流动相关的不利计算成本。概念验证模拟表明，在最小跨度渠道的流量足以捕捉向下的速度偏移，即哈马粗糙度函数，预测在全跨度渠道的流量。我们考虑两组模拟，第一次与建模的粗糙度施加的体力，第二次与明确的粗糙度所描述的粗糙度一致的网格。由于最低的成本，我们能够进行DNS与粗糙度雷诺数增加，同时保持一个固定的阻塞比，是典型的全尺寸应用。该方法为直接从粗糙表面的轮廓测量数据表征流体阻力提供了一种实用、快速和准确的工具。
英文摘要：
We describe a fast direct numerical simulation (DNS) method that promises to directly characterise the hydraulic roughness of any given rough surface, from the hydraulically smooth to the fully rough regime. The method circumvents the unfavourable computational cost associated with simulating high-Reynolds-number flows by employing minimal-span channels (Jimenez & Moin 1991). Proof-of-concept simulations demonstrate that flows in minimal-span channels are sufficient for capturing the downward velocity shift, that is, the Hama roughness function, predicted by flows in full-span channels. We consider two sets of simulations, first with modelled roughness imposed by body forces, and second with explicit roughness described by roughness-conforming grids. Owing to the minimal cost, we are able to conduct DNSs with increasing roughness Reynolds numbers while maintaining a fixed blockage ratio, as is typical in full-scale applications. The present method promises a practical, fast and accurate tool for characterising hydraulic resistance directly from profilometry data of rough surfaces.
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