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Method to minimize polymer degradation in drag-reduced non-Newtonian turbulent boundary layers
Measurement Science and Technology ( IF 2.7 ) Pub Date : 2021-05-28 , DOI: 10.1088/1361-6501/abff81
Lucia Baker 1 , Yiming Qiao 2 , Sina Ghaemi 3 , Filippo Coletti 1, 4
Affiliation  

Polymer solutions are often used to produce drag-reduced fluid flows, in which the drag reduction is achieved due to the solutions’ non-Newtonian shear-thinning and viscoelastic properties. However, experiments using polymer solutions are typically challenging due to the tendency of the polymer to degrade when subjected to intense shearing. The degradation reduces the amount of drag reduction as the experiment progresses, which limits the experiment duration and the accuracy of the results. Here we introduce a method to avoid the degradation of the polymer solution by driving the flow with a paddlewheel instead of a conventional pump. The solution is shown to undergo very little degradation during the paddlewheel’s operation. The method is then applied to perform novel measurements of a drag-reduced turbulent boundary layer at two different Reynolds numbers, both with and without a suspended particle phase. The effects of carrier fluid rheology and Reynolds number on the particle concentration and velocity profiles are explored, as well as the effect on total drag of the flow. For a given fluid type and Reynolds number, the drag is found to be nearly constant with the global particle volume fraction, suggesting that the particles have a limited ability to modulate the drag. Remarkably, the particle velocity fluctuations are greater in the non-Newtonian cases, possibly due to enhanced collisions in the near-wall region.



中文翻译:

在减阻的非牛顿湍流边界层中最大限度地减少聚合物降解的方法

聚合物溶液通常用于产生减阻流体流,其中由于溶液的非牛顿剪切稀化和粘弹性特性而实现减阻。然而,由于聚合物在受到强烈剪切时容易降解,因此使用聚合物溶液的实验通常具有挑战性。随着实验的进行,降解减少了减阻量,这限制了实验持续时间和结果的准确性。在这里,我们介绍了一种通过用桨轮而不是传统泵驱动流动来避免聚合物溶液降解的方法。该解决方案显示出在桨轮运行期间几乎没有退化。然后应用该方法对具有和不具有悬浮颗粒相的两种不同雷诺数下的减阻湍流边界层进行新的测量。探讨了载液流变学和雷诺数对粒子浓度和速度分布的影响,以及对流动总阻力的影响。对于给定的流体类型和雷诺数,发现阻力与全局颗粒体积分数几乎恒定,这表明颗粒调节阻力的能力有限。值得注意的是,在非牛顿情况下,粒子速度波动更大,可能是由于近壁区域的碰撞增强。探讨了载液流变学和雷诺数对粒子浓度和速度分布的影响,以及对流动总阻力的影响。对于给定的流体类型和雷诺数,发现阻力与全局颗粒体积分数几乎恒定,这表明颗粒调节阻力的能力有限。值得注意的是,在非牛顿情况下,粒子速度波动更大,可能是由于近壁区域的碰撞增强。探讨了载液流变学和雷诺数对粒子浓度和速度分布的影响,以及对流动总阻力的影响。对于给定的流体类型和雷诺数,发现阻力与全局颗粒体积分数几乎恒定,这表明颗粒调节阻力的能力有限。值得注意的是,在非牛顿情况下,粒子速度波动更大,可能是由于近壁区域的碰撞增强。

更新日期:2021-05-28
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