Direct numerical simulation of large-eddy-break-up devices in a boundary layer
Direct numerical simulation of large-eddy-break-up devices in a boundary layer
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DOI：
10.1016/j.ijheatfluidflow.2006.03.014
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发表时间：
2006-10-01
影响因子：
2.6
通讯作者：
Travin, A.
中科院分区：
文献类型：
--
作者：
Spalart, P. R.;Strelets, M.;Travin, A.
湍流边界层会在所有车辆内部产生空气动力学噪声，尤其是在喷气式客机内部。该项目的目的是修改附加边界层中的湍流，不是为了减少表面摩擦，而是为了减弱壁面压力波动，或者将它们转移到破坏性较小的频率和波长。为了使整个客机挡风玻璃受益，该效果将在大约25个边界层厚度delta上持续，这远远超过了湍流松弛需要大约10 delta的常见规则。采用直接数值模拟的方法对各种流动控制装置进行了研究，该方法无需建模，并提供了压力场的全部细节。雷诺数远低于真实的流，但DNS的这种限制是可以容忍的，因为重点是较大的涡流。多块隐式数值方法可以以可管理的成本表示相当复杂的器件。来流紊流是由源自隆德、吴和斯奎尔斯的循环程序提供的，但要简单得多。它在流向上所占的面积小于56。流动可视化，雷诺应力，和光谱显示;基线光谱内的实验散射。首先尝试同向旋转涡流发生器。正如所希望的那样，它们降低了远离壁面的湍流强度，但实际上加剧了壁面压力波动，因此被放弃了。接下来尝试了类似于公路桥的大涡流破碎装置，并成功地减少了壁面波动，但仅超过约6个三角洲。因此，该技术对于挡风玻璃还不成功，但它可能应用于其他窗户或其他车辆，并且模拟方法似乎已经得到很好的开发，并且特别是关于流入条件的一些兴趣。(C)2006年爱思唯尔公司All rights reserved.
Turbulent boundary layers create aerodynamic noise inside all vehicles, and especially inside jetliners. The objective of this project is to modify the turbulence in an attached boundary layer, not to reduce skin friction, but to weaken the wall pressure fluctuations, or to shift them to less damaging frequencies and wavelengths. In order to benefit an entire airliner windshield, the effect would be sustained over about 25 boundary-layer thicknesses, delta, which far exceeds the common rule that the relaxation of the turbulence takes about 10 delta. Various flow-control devices are studied by Direct Numerical Simulation, which is free of modeling and provides the full details of the pressure field. The Reynolds number is far lower than in the real flow, but this limitation of DNS is tolerable, because the focus is on the larger eddies. The multi-block implicit numerical method can represent fairly complex devices at a manageable cost. Inflow turbulence is provided by a recycling procedure derived from that of Lund, Wu and Squires, but much simpler. It occupies less than 56 in the streamwise direction. Flow visualizations, Reynolds stresses, and spectra are shown; the baseline spectra are within the experimental scatter. Co-rotating vortex generators are tried first. They reduce the turbulence intensity away from the wall, as hoped, but actually intensify the wall pressure fluctuations and were therefore abandoned. Large-eddy-break-up devices resembling a highway bridge are tried next, and succeed in reducing the wall fluctuations, but only over about 6 delta. Thus, the technology is not successful yet for a windshield, but it might be applied to other windows or other vehicles, and the simulation methodology appears to be well developed and of some interest particularly regarding inflow conditions. (C) 2006 Elsevier Inc. All rights reserved.