通过矩形管道压降实验研究了壁面微沟槽和表面活性剂的减阻性能及联合减阻的增益效果，用粒子成像测速仪分析了流场特性。实验所用的微沟槽为3种不同结构的顺流向V形沟槽，表面活性剂为十六烷基三甲基氯化胺(CTAC)，水杨酸钠(NaSal)作为补偿离子。结果表明，壁面微沟槽和表面活性剂溶液均有减阻效果，二者耦合后减阻率进一步提升，最高减阻率为48.26%。微沟槽的减阻性能主要作用在近壁区，通过影响边界层平均流速、速度脉动强度和涡结构，减少表面活性剂的湍动能损耗。当超过表面活性剂的临界雷诺数后，沟槽尖端的高剪切力会加剧胶束结构分解。表面活性剂能抑制湍流涡的演变，扩大微沟槽有效减阻的雷诺数范围。
At present, there are still few studies on the collaborative drag reduction of microgroove and surfactant in pipelines, there is still insufficient understanding of the mechanism of synergistic drag reduction between the two. In this work, the pressure drop was tested to compare the drag reduction performance of the grooved pipe on water and surfactant solution, and the turbulent structure of the flow field was analyzed by PIV system to explore the mechanism of coupling drag reduction. The microgrooves were longitudinal V-shaped grooves with three different structures, and cetyltrimethyl ammonium chloride (CTAC) was used as surfactant, and sodium salicylate (NaSal) was used as adjoint ion. The results showed that in a certain range of Reynolds number, both the wall microgroove and the surfactant solution had a drag reducing effect. The highest resistance reduction rate of water and surfactant were 6.72% and 7.12%, the highest drag reduction rate of surfactant solution was 45.14%, and the highest drag reduction ratio of coupling drag reduction was 48.26%. The drag reduction performance of the surfactant was closely related to the shear induced structure (SIS). When the critical Reynolds number was exceeded, the high shear force at the tip of the trench aggravated the damage to the SIS. The drag reduction of the microgroove on the surfactant mainly occurred in the near-wall region. By raising the average flow velocity in the near-wall region, reducing the Reynolds shear stress, and suppressing the pulsation strength of the phase velocity, the surfactant solution was provided more stable and orderly. Surfactants delayed the evolution of turbulent eddies and expanded the effective range of microgroove drag reduction. The effect of the microgroove on the drag reduction of the surfactant further improved the drag reduction rate and provided a basis for the combined drag reduction of the microgroove and the surfactant.
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