李世隆, 杨晓雷, 袁先旭, 等. 粗糙元取向对湍流统计量影响的数值研究[J]. 空气动力学学报, 2023, 41(4): 73−83. doi: 10.7638/kqdlxxb-2022.0108
引用本文: 李世隆, 杨晓雷, 袁先旭, 等. 粗糙元取向对湍流统计量影响的数值研究[J]. 空气动力学学报, 2023, 41(4): 73−83. doi: 10.7638/kqdlxxb-2022.0108
LI S L, YANG X L, YUAN X X, et al. Numerical study on the orientation effects of roughness elements on turbulence statistics[J]. Acta Aerodynamica Sinica, 2023, 41(4): 73−83. doi: 10.7638/kqdlxxb-2022.0108
Citation: LI S L, YANG X L, YUAN X X, et al. Numerical study on the orientation effects of roughness elements on turbulence statistics[J]. Acta Aerodynamica Sinica, 2023, 41(4): 73−83. doi: 10.7638/kqdlxxb-2022.0108

粗糙元取向对湍流统计量影响的数值研究

Numerical study on the orientation effects of roughness elements on turbulence statistics

  • 摘要: 采用直接数值模拟方法研究了椭球体粗糙元取向对粗糙壁槽道湍流统计量的影响,其中,粗糙元几何采用清晰界面浸没边界方法直接解析。考虑了四种不同粗糙元取向的粗糙壁,包括随机取向、垂直放置、朝下游倾斜45°、朝上游倾斜45°,对于每种取向选取三种不同粗糙元间距。模拟结果显示:粗糙元取向对湍流统计量有显著影响;对于小粗糙元间距( l = 2.0r ,其中 r 为椭球体的最短半轴长),“随机取向”粗糙壁的砂粒粗糙度长度( k_s )大于其他粗糙壁;对于大粗糙元间距( l = 2.8r 3.5r ),“垂直放置”粗糙壁的 k_s 最大;“朝下游倾斜45°”和“朝上游倾斜45°”粗糙壁的 k_s 值和雷诺正应力(以壁面摩擦速度无量纲化)基本相同,并且其流向雷诺正应力远高于其他粗糙壁。另一方面,“朝下游倾斜45°”粗糙壁的流向分散应力高于 “朝上游倾斜45°”粗糙壁;垂向和横向分散应力远小于流向分散应力,其中“随机取向”粗糙壁的垂向和横向分散应力幅值最高。

     

    Abstract: This paper employs Direct Numerical Simulation to study the orientation effects of ellipsoid roughness elements on the statistics of rough-wall turbulent channel flows. Roughness elements are directly resolved using a sharp-interface immersed boundary method. The simulations consider roughness elements with four different orientations, namely random orientation, vertical placement, inclined 45° downstream, and inclined 45° upstream. For each orientation, three different roughness element spacings are considered. Numerical results show that the roughness elements’ orientation significantly affects turbulence statistics. For a small roughness element spacing (i.e. l = 2.0r, where ris the minor semi-axis length of the ellipsoid), the randomly oriented roughness elements result in the largest sandgrain roughness length (ks); for large roughness elements spacing (i.e. l = 2.8r and 3.5r), ks of the vertically placed roughness elements is the largest. The value of ks and the Reynolds normal stresses in viscous units of the roughness elements inclined 45° downstream or upstream are nearly the same; the streamwise Reynolds normal stress is much higher than those of other rough walls. On the other hand, the streamwise dispersive stress of roughness elements inclined 45° downstream is higher than that of the opposite orientation. The vertical and spanwise dispersive stresses are much smaller than the streamwise one. Randomly oriented roughness elements yield the strongest vertical and spanwise dispersive stresses.

     

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