航空学报 > 2020, Vol. 41 Issue (10): 123814-123814   doi: 10.7527/S1000-6893.2020.23814

微吹气对湍流平板边界层流动特性的影响及其减阻机理

范云涛, 张阳, 叶志贤, 邹建锋, 郑耀   

  1. 浙江大学 航空航天学院, 杭州 310027
  • 收稿日期:2020-01-09 修回日期:2020-03-02 发布日期:2020-02-27
  • 通讯作者: 张阳 E-mail:yangzhang@zju.edu.cn
  • 基金资助:
    中华人民共和国工业和信息化部-欧盟委员会航空科技合作项目(690623)

Micro-blowing: Effect on flow characteristics in turbulent flat plate boundary layer and drag reduction mechanism

FAN Yuntao, ZHANG Yang, YE Zhixian, ZOU Jianfeng, ZHENG Yao   

  1. School of Aeronautics and Astronautics, Zhejiang University, Hangzhou 310027, China
  • Received:2020-01-09 Revised:2020-03-02 Published:2020-02-27
  • Supported by:
    DRAGY (690623)

摘要: 微吹气技术能够改变平板湍流流场结构,减小平板表面的摩擦阻力。采用直接数值模拟方法,计算了来流马赫数0.7条件下,流场流过光滑平板和NASA-PN2多孔平板表面两种情况,通过对比这两个算例的相关流场特征,验证了微吹气控制减阻的有效性,局部最大减阻率达到了45%,并且由于微吹气控制的"记忆"功能,减阻效果在微吹气流域下游仍会持续一段距离,增加了减阻区域的流向面积。壁湍流摩擦减阻的原因在于近壁区域出现了一个低速的"湍流斑",黏性底层厚度增加,速度型曲线被抬升。但与此同时,边界层内湍流速度脉动也得到了增强。进一步对流向脉动涡演化规律分析,发现微吹气对流向脉动涡发挥着多重作用。在增加流向脉动涡强度的同时,还使得流向涡团向远离壁面抬升,这样减小了流向涡与壁面之间直接作用。此外,微吹射流产生的冲击作用会在流向涡表面留下凹痕,使得流向涡分散成相对小的涡团结构。

关键词: 微吹气技术, 湍流结构, 减阻, 湍流强度, 涡量

Abstract: Micro-blowing technology can change the turbulent structure in a flat plate flow and reduce the wall friction drag. In this paper, two cases of inflow through a smooth plate and a NASA-PN2 porous plate at Mach number 0.7 are respectively resolved by direct numerical simulation. Comparison of the flow characteristics in the two cases proves the effectiveness of micro-blowing technology on drag reduction, with the maximum rate reaching 45%. Furthermore, because of the "memory" function controlled by micro-blowing, the effect will last for a certain distance in the downstream, thus expanding the area of drag reduction. The explanation for the drag reduction in a wall turbulent boundary layer is the production of a low-speed "turbulence spot" in the near-wall region, which increases the thickness of viscous sub-layer and uplifts the average velocity profile. However, the turbulent velocity fluctuations in the boundary layer are strengthened simultaneously. Further analysis of the evolution of stream-wise vortex fluctuations reveals that micro-blowing plays multiple roles. It not only enhances the intensity of stream-wise vortex fluctuations, but also uplifts the stream-wise vortex clusters away from the wall, hence directly reducing the interaction between the stream-wise vortex and the wall surface. In addition, the impact caused by micro-blowing will leave dents on the vortex surface, leading to more dispersed and finely broken vortex clusters.

Key words: micro-blowing technology, turbulent structure, drag reduction, intensity of turbulence, vorticity

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