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中文核心期刊

固体颗粒对沟槽湍流边界层影响的实验研究

EXPERIMENTAL STUDY ON THE EFFECT OF SOLID PARTICLES ON RIBLET-PLATE TURBULENT BOUNDARY LAYER

  • 摘要: 本文采用粒子图像测速技术(particles image velocimetry, PIV)研究固体颗粒对放置在平板湍流边界层中的平壁和沟槽壁面减阻效果的影响. 实验对清水和加入粒径为155 μm聚苯乙烯颗粒的流法向二维速度场信息进行采集, 对不同工况下的平均速度剖面、雷诺应力和湍流度等统计量进行对比, 分析流体在边界层中的行为. 运用空间局部平均结构函数提取了不同工况湍流边界层喷射−扫掠行为的空间拓扑结构并进行比较. 结果发现, 在不同的壁面条件下, 粒子加入后的对数律区中无量纲速度均略大于清水组, 雷诺切应力有所降低, 湍流度有所减弱. 对于不同流场速度下的沟槽而言, 颗粒的加入均降低了壁面附近的阻力, 而颗粒单独作用于光滑壁面的减阻效果并不明显. 加入粒子后的相干结构数目有所增加, 法向脉动速度下降. 沟槽壁面附近的相干结构数目有所增加, 法向脉动速度在自由来流速度较大时有所上升, 在速度较小时有所下降. 这表明不同减阻状况下的沟槽均能将大涡破碎成更多的涡, 并且粒子的加入强化了这种破碎作用.

     

    Abstract: The particle image velocimetry (PIV) is used to conduct experimental research in the solid-liquid two-phase wall turbulent boundary layer in smooth and riblet surface. The streamwise-normal two-dimensional velocity field information of clean water (as single phase) and water with polystyrene particles which diameter is 155 μm was collected, and the turbulence statistics such as the average velocity profile, turbulence intensity and Reynolds shear stress of the smooth and riblet surface are compared in particle phase and clean water to analyze the behavior of fluid in different wall boundary layers. Coherent structures were detected by quadrant splitting method and the concept of local average velocity structure functions of the streamwise is utilized to extract the sweep and eject motions under different operating conditions. Under the different wall conditions, the dimensionless fluid velocity with particles was greater than that of clean water, the Reynolds stress in the logarithmic law region is decreased and the turbulence intensity is receded. The addition of particles reduces the drag reduction near the riblet surface with different velocities, but the drag reduction effect of particles acting on smooth wall surface is not obvious. The number of coherent structures is increased with the addition of particles and the normal fluctuating velocity is decreased. The number of coherent structures is increased near the riblet surface, the normal fluctuating velocity is increased in a higher free flow velocity and the normal fluctuating velocity is decreased in a lower free flow velocity. This indicates that the large vortices can be broken into more vortices under different drag reduction conditions, and this effect is increased by the addition of particles.

     

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