高分子溶液对湍流边界层减阻机理的实验研究  

Experimental investigation of drag reduction in turbulent boundary layer with polymer additives solution

作　　者：王超伟 杨绍琼 姜楠[1,2] WANG Chaowei;YANG Shaoqiong;JIANG Nan(School of Mechanical Engineering,Tianjin University,300354,Tianjin,China;Tianjin Key Laboratory of Modern Engineering Mechanics,300354,Tianjin,China)

机构地区：[1]天津大学机械工程学院,天津300354 [2]天津市现代工程力学重点实验室,天津300354

出　　处：《应用力学学报》2021年第6期2384-2391,共8页Chinese Journal of Applied Mechanics

基　　金：国家自然科学基金项目(11732010,11972251,11902218)。

摘　　要：采用TRPIV实验测量了不同雷诺数下聚丙烯酰胺(PAM)溶液的平板湍流边界层的速度场。研究结果表明:在加入少量PAM后,湍流边界层壁面阻力出现降低,并且减阻率随雷诺数的升高而增大;PAM湍流的平均速度剖面的对数律区与清水湍流具有相同的斜率,但具有更高的法向位置。与清水湍流相比,PAM湍流的脉动速度的强度明显减弱,雷诺切应力显著减小。通过采用改进的基于空间局部平均速度结构函数的象限分裂法以及新型条件采样法计算了湍流猝发事件中各物理量的空间相位平均场。其结果表明作为雷诺切应力主要来源的喷射和扫掠事件,在近壁区受到明显抑制。Time-resolved particle image velocimetry(TRPIV) was performed to investigate the drag reduction characteristics of polymer solution. Turbulent boundary layer was measured in a water channel with different Reynolds numbers. The drag-reducing solution was an aqueous solution of polyacrylamide with a mass concentration of 190 ppm. The results of the study showed that wall friction velocity, wall friction stress and wall friction coefficient decreased when small amounts of polymers were added. With the increase of Reynolds number,drag reduction rate became larger. Compared to that of the water flow, the mean velocity profile in the logarithmic region for drag-reducing flow had the same slope, but shifted upward in the log-law and the buffer region thickened,which had the obvious drag reduction performance. A prominent decrease in turbulence intensities(r.m.s.of streamwise velocity fluctuations and wall normal velocity fluctuations) and Reynolds shear stress were noted for polymer solution compared to those for water flow. An improved quadrant splitting method based on the spatial local-averaged velocity structure function was employed to analyze the statistics of streamwise direction by space phase average topology of various physical quantities about coherent structures. The ejection and sweep intensities of coherent structures in wall turbulent flow are significantly inhibited for polymer solution in the near wall region which is considered as the main contributor to Reynolds shear stress.

关 键 词：湍流边界层 减阻 高分子 TRPIV 局部平均速度结构函数 

分 类 号：O357.5[理学—流体力学]