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Effect of Polymer on Drag Reduction in a Sudden Enlargement of Pipe Cross Section

机译：突然增大管道横截面中聚合物对减阻的影响

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The purpose of the present paper is to study experimentally the effect of drag reducing polymers on loasses due to friction and sudden enlargement of pipe cross section. Polymers used in this research include copolymer of acrylamaide with a cationic acid (ACA) and sodium carboxymethyl cellulose (CMC). Two different geometeries were considered, a sudden enlargement in pipe diameter from 27 to 40.5 mm diameter ratio (DR) of 1 : 1.75, and (b) from 27 to 54 mm (DR =1 : 2). The effect of Reynolds number change, polymer type, polymer concentration, and area ratio were studied. The upstream Reynolds number was varied from 5 × 10~4 to 10~5 and polymer concentration from 3 to 32 ppm inside the test section. The experimental results showed that the percent drag reduction increases with increasing both Reynolds number and polymer concentration. Drag reduction up to 63.47% was obtained at 5 × 10~4 Reynolds with 32 ppm of ACA in upstream side and drag reduction reappears in downstream side when it was large in the upstream side. While CMC was not effective when used as a drag reducing agent in this range of concentration. Moreover, the sudden enlargement factor was decreased by 18% when using 32 ppm of ACA at 5 × 10~4 Reynolds number. Also, using ACA as a drag reducing agent enhances pressure distribution in the upstream and downstream pipe flow.
机译：本文的目的是通过实验研究减阻聚合物对黄土由于摩擦和管道横截面突然增大的影响。本研究中使用的聚合物包括丙烯酰胺与阳离子酸（ACA）和羧甲基纤维素钠（CMC）的共聚物。考虑了两个不同的几何形状，管径突然从27：40.5 mm的直径比（DR）扩大为1：1.75，（b）从27 mm扩大到54 mm（DR = 1：2）。研究了雷诺数变化，聚合物类型，聚合物浓度和面积比的影响。在测试区内，上游的雷诺数从5×10〜4变到10〜5，聚合物浓度从3到32 ppm。实验结果表明，减阻百分数随雷诺数和聚合物浓度的增加而增加。在5×10〜4雷诺数下，在上游侧的ACA为32 ppm时，减阻率高达63.47％，而在上游侧变大时，减阻率又出现在下游侧。当在该浓度范围内用作减阻剂时，CMC无效。此外，当在5×10〜4雷诺数下使用32 ppm的ACA时，突然增大因子降低了18％。同样，使用ACA作为减阻剂可增强上游和下游管道流动中的压力分布。

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