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蔡书鹏, 汪志能, 段传伟, 李丹. 表面活性剂减阻水溶液突扩流的阻力特性[J]. 力学学报, 2018, 50(2): 274-283. DOI: 10.6052/0459-1879-17-328
引用本文: 蔡书鹏, 汪志能, 段传伟, 李丹. 表面活性剂减阻水溶液突扩流的阻力特性[J]. 力学学报, 2018, 50(2): 274-283. DOI: 10.6052/0459-1879-17-328
Cai Shupeng, Wang Zhineng, Duan Chuanwei, Li Dan. DRAG CHARACTERISTICS OF A DRAG-REDUCING SURFACTANT SOLUTION FLOWING OVER A SUDDEN-EXPANSION PIPE[J]. Chinese Journal of Theoretical and Applied Mechanics, 2018, 50(2): 274-283. DOI: 10.6052/0459-1879-17-328
Citation: Cai Shupeng, Wang Zhineng, Duan Chuanwei, Li Dan. DRAG CHARACTERISTICS OF A DRAG-REDUCING SURFACTANT SOLUTION FLOWING OVER A SUDDEN-EXPANSION PIPE[J]. Chinese Journal of Theoretical and Applied Mechanics, 2018, 50(2): 274-283. DOI: 10.6052/0459-1879-17-328

表面活性剂减阻水溶液突扩流的阻力特性

DRAG CHARACTERISTICS OF A DRAG-REDUCING SURFACTANT SOLUTION FLOWING OVER A SUDDEN-EXPANSION PIPE

  • 摘要: 为揭示胶束水溶液突扩流的减阻特性,实验研究了质量分数为1×10-4, 2 ×10-4的十六烷基三甲基溴化铵水溶液通过管径比为1:1.52的突扩的流动阻力行为. 实验结果表明,在直管段最大减阻率都可达到70%的两给定质量分数的胶束水溶液,其突扩局部阻力系数,在较低雷诺数区域,较牛顿流体仅有10%~20%程度的降低,呈现局部低减阻特性;在较高雷诺数区域远大于牛顿流体,尤其当突扩进口流快失去减阻能力时,甚至接近牛顿流体的1.5倍,呈现明显的局部增阻行为. 胶束水溶液减阻流,在突扩下游再次形成充分发展流所需的下游长度,远大于牛顿流体的7.8倍下游管径(45倍突扩台阶高度),流入突扩前完全失去减阻能力的质量分数为2×10-4的胶束水溶液流,所需的突扩下游长度达到最大,约合158倍下游管径(920倍突扩台阶高度). 通过胶束水溶液流变特性的实验分析认为,减阻水溶液突扩流的阻力行为与它的胶束网联结构的形成及松弛的时间特性密切相关.

     

    Abstract: The minor loss characteristics of a drag-reducing surfactant solution flowing over a circular sudden-expanded pipe have been investigated experimentally with an expansion ratio of 1:1.52. The surfactant used is cetyltrimethyl ammonium bromide (CTAB) with concentrations of 1×10 - 4 and 2×10-4 by weight. The maximum drag reduction rate for both solutions is achieved 70% in the fully developed flow in straight pipes. But at lower inlet Reynolds numbers than the critical one, the expansion loss coefficient is only 10%~20% below that for water, while at inlet Reynolds numbers much higher than the critical one, it is found to be much greater than that for water and to approach 1.5 times one for water at the Reynolds number at which the friction factor reaches that for water. Furthermore, a much longer distance is required for the micelle solution flowing across the sudden-expanded step, than 7.8 times the diameter (45 times the step height) of expansion-downstream pipe for water in order to reform a fully developed flow in the downstream. And as inlet flow for the solution of concentration 2 ×10-4 loses its drag-reducing efficiency, approximately 158 times diameter (920 times the step height) of the expansion downstream pipe is necessary for reforming the fully developed drag-reducing flow in the downstream. From the present rheological measuring results for the surfactant solutions, the drag and its development behaviour of the sudden expansion pipe can be considered to be closely related to the time characteristics in forming and relaxing of the netlike micelle structure induced by shearing.

     

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