Effect of Reynolds number on drag reduction: from near-wall cycle to large-scale motions.

雷诺数对减阻的影响：从近壁循环到大规模运动。

• 批准号: 2345157
• 负责人: Yulia Peet
• 金额: $ 32.97万
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-03-01 至 2027-02-28
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2345157&HistoricalAwards=false
• 关键词: Effect; Reynolds; number; drag; reduction

The problem of reducing drag on the objects in contact with viscous fluids moving relative to them is of great importance due to high economic and energy benefits associated with such drag reduction. The drag is known to increase when the relative velocity (correspondingly, the Reynolds number of the flow) increases, while many of the common drag reduction techniques are known to lose effectiveness with the increase in Reynolds number. This project will investigate the reasons for this loss of effectiveness and propose new strategies that may potentially overcome this limitation. In particular, a drag reduction mechanism in fluids flowing across a pipe that imparts a certain motion to the walls of the pipe will be considered. A hypothesis that specific parameters (such as frequency and wavelength) of such wall motions significantly influence the drag reduction will be investigated, via high-fidelity computational simulations across the range of Reynolds numbers. The project will also seek to improve the quality of education of fundamental mathematical and physical disciplines for the engineering students, via enhancing the course curriculum, engaging undergraduate students in research, and conducting outreach activities to underrepresented students across the metropolitan Phoenix area.The project will investigate the hypothesis that the loss of performance of some common drag reduction mechanisms with increase in Reynolds number is associated with the increasing influence of large scales which may not be efficiently controlled by conventional drag reduction mechanisms. In particular, the traditional inner-scaled actuation and a less investigated outer-scaled actuation mechanisms will be compared and analyzed on an example of a turbulent pipe flow with streamwise traveling waves of transverse wall velocity as a drag reduction mechanism. Depending on the frequency and the wavelength of a traveling wave, different scales of motions in a turbulent flow will be actuated, and their role in drag reduction depending on the Reynolds number will be quantified. Additionally, a novel approach that targets small and large scales of flow simultaneously, termed a multi-scaled actuation, will be investigated. This new approach promises to overcome the limitations of previously explored methods, especially at high Reynolds number flows. Enhancing the capabilities to reduce skin friction drag at increased Reynolds numbers, approaching the target for realistic applications, will have a strong impact on the world economy, global energy usage, and emission reductions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

由于与这种减阻相关的高经济和能源效益，减少与相对于其运动的粘性流体接触的物体上的阻力的问题非常重要。众所周知，当相对速度（相应地，流动的雷诺数）增加时，阻力会增加，而许多常见的减阻技术会随着雷诺数的增加而失去有效性。该项目将调查这种有效性丧失的原因，并提出可能克服这一限制的新策略。特别地，将考虑流过管道的流体中的减阻机构，该机构向管道壁赋予一定的运动。将通过雷诺数范围内的高保真计算模拟来研究这样的壁运动的特定参数（例如频率和波长）显着影响减阻的假设。该项目还将通过加强课程设置、吸引本科生参与研究以及针对凤凰城地区代表性不足的学生开展外展活动，寻求提高工程专业学生基础数学和物理学科的教育质量。该项目将研究这样的假设：随着雷诺数的增加，一些常见的减阻机制的性能损失与大尺度的影响不断增加有关，而传统的减阻机制可能无法有效地控制这种影响。特别是，将以具有横向壁速度的流向行波作为减阻机制的湍流管流为例，对传统的内尺度驱动和较少研究的外尺度驱动机制进行比较和分析。根据行波的频率和波长，将启动湍流中不同规模的运动，并且根据雷诺数对它们在减阻中的作用进行量化。此外，还将研究一种同时针对小规模和大规模流量的新方法，称为多尺度驱动。这种新方法有望克服以前探索的方法的局限性，特别是在高雷诺数流量下。提高雷诺数增加时减少表面摩擦阻力的能力，接近实际应用的目标，将对世界经济、全球能源使用和减排产生重大影响。该奖项反映了 NSF 的法定使命，并被认为是值得的通过使用基金会的智力优势和更广泛的影响审查标准进行评估来提供支持。