Modification of Near-Wall, High-Reynolds Number Velocity Profiles With Polymer Solution

在流体中加入极少量的聚合物可以显著减少湍流中的摩擦。建议在新建的设施中进行最先进的实验，以获得不同条件下该过程的大量详细数据，然后建立聚合物对流体速度影响的预测模型。聚合物减阻可用于长距离流体输送，例如石油管道，从而节省能源。它还可以降低海洋航行工具（船舶和潜艇）的能源成本。提出的研究是研究减阻聚合物溶液如何改变高雷诺数湍流边界层的近壁区域。虽然这已经被认为被理解了几十年，但最近的数值和实验数据显示出与经典观点的重大偏差。现有数据显示，当阻力降低超过40%时，这种现象并不普遍，这只能部分地用雷诺数效应来解释。因此，这种行为必须取决于聚合物的性质。因此，本项目将重点研究不同减阻值、雷诺数和聚合物性质（即Weissenberg数、粘度比和长度比）下近壁区域的特征。第一个目标是在聚合物海洋中进行这种表征，以消除非均匀聚合物浓度场的影响。然后用聚合物注射重复测试，以评估剖面对浓度场均匀性的敏感性。最后，将在聚合物海洋和注入聚合物的情况下重新检查最终剖面，即经验推导的速度偏移上限，以确定数值和实验观测的有效性，即剖面不是对数的。还将审查在什么条件下可以实际超过此配置文件。除了研究生和本科生的参与外，高中生还将通过PI参与俄克拉荷马州立大学向上发展计划的工作影子部分参与研究，该计划主要针对低收入和/或第一代高中生。每年，这些学生中最多有3人将与PI一起工作6周。

PI: Elbing, BrianProposal Number: 1604978The addition of a very small amount of polymers to a fluid can result in a dramatic reduction of friction for turbulent flows. It is proposed to conduct state-of-the-art experiments in a newly built facility to obtain an extensive amount of detailed data for the process at different conditions, and then develop a predictive model for the polymer effects on the fluid velocity. Drag reduction with polymers can be used to save energy for fluid transportation over long distances, e.g., for oil pipelines. It can also reduce energy costs for ocean faring vehicles (ships and submarines). The proposed research is to investigate how drag-reducing polymer solutions modify the near-wall region of a high-Reynolds number turbulent boundary layer. While this has been thought to be understood for decades, recent numerical and experimental data show significant deviation from the classical view. Available data shows a non-universal behavior when the drag reduction is above 40%, which can only be partially explained by a Reynolds number effect. Consequently, the behavior must be dependent on polymer properties. Thus, this project will focus on characterizing the near-wall region at various values of drag reduction, Reynolds number and polymer properties (i.e., Weissenberg number, viscosity ratio, and length ratio). The first objective is to perform this characterization in a polymer ocean to eliminate the influence of a non-homogeneous polymer concentration field. Then testing will be repeated with polymer injection to assess the sensitivity of the profiles to the homogeneity of the concentration field. Finally, the ultimate profile, an empirically derived upper limit for the velocity shift, will be reexamined in both a polymer ocean and with polymer injection to determine the validity of numerical and experimental observations that the profile is not logarithmic. It will also be examined under what conditions this profile can actually be exceeded. In addition to graduate and undergraduate student participation, high-school students will be engaged in research through the PI's involvement with the job-shadowing component of Oklahoma State University's Upward Bound program, which is focused on low-income and/or first generation high school students. Each year, up to 3 of these students would work with the PI for 6 weeks.