Large Eddy Simulation of separating flows from curved surfaces
Large Eddy Simulation of separating flows from curved surfaces
复制标题
曲面分离流的大涡模拟
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
L. Temmerman
中科院分区：
文献类型：
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作者：
L. Temmerman
大涡模拟在高雷诺数下预测曲面分离的能力和局限性是本论文的中心内容。特别感兴趣的问题是网格分辨率、次网格尺度建模和旨在降低计算成本的近壁近似。文中分析了两种情况：一种是在具有流动周期收缩(丘陵)的通道中分离的流动，另一种是雷诺数为2.1的单段高升力翼型绕流。106.在这些研究之前，考虑的是完全发展的河道水流模拟。这些结果表明，在次网格尺度粘性量级及其壁面渐近变化方面，次网格尺度模式之间存在显著差异。建模和数值误差似乎相互抵消，从而减少了总误差。墙函数被证明是一种经济有效的方法，在接近平衡的条件下提供了一个相当准确的近似。然而，要实现成功的模拟，足够的分辨率仍然至关重要。在山丘流中，分离发生在山顶下游，重新连接发生在两个连续山丘之间的中途，部分恢复发生在下一个山丘重新加速之前。为产生基准数据而进行的高分辨率模拟允许对流动特性进行广泛的研究。然后将较粗的网格模拟与前者进行比较。这突出了分离点附近的流型离散化的影响和壁面处理的实施细节所起的作用，而次网格尺度模式的影响不太显著。翼型具有过渡和分离的特点，具有极大的挑战性，处于当前LES能力的边缘。所有的模拟都没有重现
The capabilities and limitations of LES in predicting separation from curved surfaces at high Reynolds number are at the centre of this Thesis. Issues of particular interest are mesh resolution, subgrid-scale modelling and near-wall approximations aiming to reduce the computational cost. Two cases are examined: a flow separating in a channel with streamwise periodic constrictions (hills), and the flow around a single-element, high-lift aerofoil at a Reynolds number of 2.1 . 106. Prior to these studies, fully-developed channel-flow simulations are considered. These show substantial differences among subgrid-scale models in terms of the subgrid-scale viscosity magnitude and its wall-asymptotic variation. Modelling and numerical errors appear to counteract each other, thus reducing the total error. Wall functions axe shown to be a cost-effective approach, providing a reasonably accurate approximation in near-equilibrium conditions. Adequate resolution remains critical, however, in achieving successful simulations. In the hill flow, separation occurs downstream of the hill crest, reattachment takes place about half-way between two consecutive hills and partial recovery occurs prior to a re-acceleration on the following hill. A highly-resolved simulation, performed to produce -benchmark data, permits an extensive study of the flow properties. Coarser mesh simulations are then compared with the former. These highlight the influence of the streamwise discretisation around the separation point and the role played by the implementation details of the wall treatments, while the subgrid-scale models influence is less significant. The aerofoil, which features transition and separation, is extremely challenging and at the edge of current LES capabilities. None of the simulations reproduce