ERI: Wake interactions past two roughness elements in close proximity to a surface

ERI：靠近表面的两个粗糙度元素的尾流相互作用

• 批准号: 2301453
• 负责人: Ali Hamed
• 金额: $ 19.82万
• 依托单位: Union College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-04-01 至 2025-03-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2301453&HistoricalAwards=false
• 关键词: ERI; Wake; interactions; past; two

The turbulent flow over two roughness elements in close proximity on an otherwise relatively smooth surface is encountered in environmental and engineering applications (e.g., two dunes in close proximity and two protrusions in close succession on an engineered surface). The interactions between the upstream wake and the downstream wake govern important flow features including drag and turbulence. This project aims to quantify and understand the wake interactions between two roughness elements in close proximity under incoming turbulent flow. For this purpose, flow measurements will be made for a wide range of configurations using state-of-the-art instrumentation. The project will be performed at an undergraduate institution providing foundation for engineering research and enhancing undergraduate research training. The project will provide engaging research experiences for undergraduate students who will gain valuable research training and mentoring while working alongside faculty.High-speed volumetric particle image velocimetry, a non-intrusive laser-diagnostic flow measurement technique, will be used to measure the flow over two cylindrical roughness elements positioned in close proximity and immersed in a turbulent boundary layer. The cylinders will be positioned at various configurations to vary the degree by which the upstream cylinder shelters the downstream cylinder from the incoming high-momentum flow. The experiments will allow for the characterization of rich flow physics: the interaction of two 3D shear layers in the lower portion of a turbulent boundary layer. The objectives are to 1) quantify the flow interactions between the wakes of the two cylindrical roughness elements; 2) characterize the vortical structures shed from isolated cylindrical roughness elements and identify the modifications to these structures due to the introduction of an upstream cylinder; 3) investigate the effects of additional upstream elements (i.e., sheltering by 2, 3, and 4 upstream elements) on the captured flow physics, 4) quantify the roughness-induced perturbation to the boundary layer and its coherent structures; and 5) distill a spatiotemporally-resolved flow description that illustrates sheltering flow physics across a wide range of arrangements. The spatially- and temporally-resolved measurements will aid in addressing a gap in the literature on the flow over two roughness elements in close proximity, offer insight into the rich flow physics involved, and provide benchmark results to aid other researchers in their modeling and validation efforts.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.

在环境和工程应用中，会遇到在相对光滑的表面上紧邻的两个粗糙度元素上的湍流（例如，工程表面上紧邻的两个沙丘和紧邻的两个突起）。上游尾流和下游尾流之间的相互作用控制着重要的流动特征，包括阻力和湍流。该项目旨在量化和理解传入湍流下两个非常接近的粗糙度元素之间的尾流相互作用。为此，将使用最先进的仪器对各种配置进行流量测量。该项目将在本科院校进行，为工程研究提供基础并加强本科生研究培训。该项目将为本科生提供引人入胜的研究经验，他们将在与教师一起工作的同时获得宝贵的研究培训和指导。高速体积粒子图像测速技术是一种非侵入式激光诊断流量测量技术，将用于测量流量两个圆柱形粗糙度元素紧密相连并浸入湍流边界层中。气缸将以不同的配置定位，以改变上游气缸保护下游气缸免受进入的高动量流影响的程度。这些实验将能够表征丰富的流动物理：湍流边界层下部的两个 3D 剪切层的相互作用。目标是 1) 量化两个圆柱形粗糙度元素尾流之间的流动相互作用； 2）表征从孤立的圆柱形粗糙度单元中脱落的涡流结构，并确定由于引入上游圆柱体而对这些结构的修改； 3) 研究附加上游元件（即，由 2、3 和 4 个上游元件遮挡）对捕获的流动物理的影响，4) 量化粗糙度引起的对边界层及其相干结构的扰动； 5）提炼出时空解析的流动描述，该描述说明了各种布置中的庇护流动物理现象。空间和时间分辨率的测量将有助于解决文献中有关两个邻近粗糙度元素的流动的空白，提供对所涉及的丰富流动物理的深入了解，并提供基准结果以帮助其他研究人员进行建模和验证该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。