当前位置: X-MOL 学术Flow Turbulence Combust. › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Effects of Localized Micro-blowing on a Spatially Developing Flat Turbulent Boundary Layer
Flow, Turbulence and Combustion ( IF 2.4 ) Pub Date : 2020-10-01 , DOI: 10.1007/s10494-020-00221-2
Lan Xie , Yao Zheng , Yang Zhang , Zhi-xian Ye , Jian-feng Zou

Direct numerical simulation (DNS) is used to investigate the turbulent flat-plate boundary layer with localized micro-blowing. The 32 × 32 array of micro-holes is arranged in a staggered pattern on the solid wall, located in the developed turbulent region. The porosity of the porous wall is 23%, and the blowing fraction is 0.0015. The Reynolds number based on the inflow velocity is set to be 50,000. The structures of the turbulent boundary layer are carefully analyzed to understand the effects of micro-blowing and its drag reduction mechanism. The DNS results show that the drag reduction is efficient, and the local maximum rate of drag reduction achieves 40%. A low-speed “turbulent spot” near the micro-blowing region thickens the boundary layer. Some turbulent properties, such as the mean velocity profile, stream-wise vorticity and stream-wise velocity fluctuation are lifted up. Particularly, the tilting term of vorticity transport is significantly increased. Meanwhile, the visualization of 3-dimensional vortex displays several concave marks on the surface of the near-wall vortices, which is caused by the micro-jets, leading to more broken vortices and isotropic small scales. This impact travels downstream with a small distance due to the accumulation of the micro-jets, while the uplift effect will gradually disappear. In addition, FIK identity reveals that the spatial development term and mean wall-normal convection term play opposite roles in the contribution to the skin friction drag.

中文翻译:

局部微吹对空间发展平坦湍流边界层的影响

直接数值模拟 (DNS) 用于研究具有局部微吹的湍流平板边界层。32×32的微孔阵列在固体壁面上呈交错排列,位于湍流发展区。多孔壁孔隙率为23%,发泡率为0.0015。基于流入速度的雷诺数设置为 50,000。仔细分析了湍流边界层的结构,以了解微吹的影响及其减阻机制。DNS结果表明减阻是有效的,局部最大减阻率达到40%。微吹区域附近的低速“湍流点”使边界层变厚。一些湍流特性,例如平均速度剖面,流向涡度和流向速度脉动被提升。特别是涡量输运的倾斜项显着增加。同时,三维涡旋的可视化在近壁涡旋表面显示出几个凹痕,这是由微射流引起的,导致更多的破碎涡旋和各向同性的小尺度。由于微射流的积累,这种冲击向下游传播一小段距离,而隆升效应将逐渐消失。此外,FIK 恒等式表明空间发展项和平均壁面法向对流项在对皮肤摩擦阻力的贡献中起着相反的作用。3维涡旋的可视化显示近壁涡旋表面有几个凹痕,这是由微射流引起的,导致更多的破碎涡旋和各向同性的小尺度。由于微射流的积累,这种冲击向下游传播一小段距离,而隆升效应将逐渐消失。此外,FIK 恒等式表明空间发展项和平均壁面法向对流项在对皮肤摩擦阻力的贡献中起着相反的作用。3维涡旋的可视化显示近壁涡旋表面有几个凹痕,这是由微射流引起的,导致更多的破碎涡旋和各向同性的小尺度。由于微射流的积累,这种冲击向下游传播一小段距离,而隆升效应将逐渐消失。此外,FIK 恒等式表明空间发展项和平均壁面法向对流项在对皮肤摩擦阻力的贡献中起着相反的作用。
更新日期:2020-10-01
down
wechat
bug