The Wall Pressure Field Of High Reynolds Number Rough-Wall Turbulent Boundary Layers

Devenport，William J. 本研究计划旨在揭示和更好地了解高雷诺数粗糙壁边界层产生的脉动表面压力场。该压力场在许多应用中是振动和噪声的来源。它还提供了有利于近壁动力学的加权边界层湍流结构的测量。然而，粗糙壁边界层压力波动的研究却很少。研究只包括一组有限的粗糙表面，几乎没有系统的检查粗糙度类型或稀疏的影响。最重要的是，几乎没有雷诺数和边界层粗糙度尺度比大到足以消除过渡效应的边界层测量，其中可能观察到普遍的标度和行为，并且具有最实用和科学价值。本研究的目的是：将现有的粗糙壁边界层脉动压力测量数据库扩展到高雷诺数区域，将数据库扩展到包括具有完全定义的几何形状和显著范围的尺寸和稀疏值的随机和确定性表面;利用这些数据建立粗糙壁面压力谱的低频和高频标度以及对流速度和空间压力相干函数的行为;并为包括研究生、本科生和高中生在内的不同学生群体提供尖端的研究教育。PI的实验方法集中在弗吉尼亚理工大学稳定性风洞提供的新的航空声学能力。该设备既大又安静，因此特别适合于压力波动测量和厚的、充分发展的、具有光滑或粗糙壁的高雷诺数湍流边界层的生长。一个完整的程序，高雷诺数的随机和确定性粗糙表面上的流动实验将直接解决现有知识的不足。在许多情况下，例如风力涡轮机或飞机，噪声和振动是粗糙壁湍流边界层的脉动压力场的直接结果。这项研究所产生的更好的理解将对噪声源预测的准确性产生直接影响。这对于提高这些设备的环境可接受性和经济可行性至关重要。弗吉尼亚理工大学稳定隧道是一个多用户设施，吸引了各种各样的用户，包括研究小组，商业测试和一系列本科课程。计划的工作包括两个具体的分项目，将由本科生和高中生小组进行。这些小组将在PI的指导下由参与该项目的研究生指导。这延续了大学生参与PI研究小组的悠久历史。高中生将通过现有的计划与西南弗吉尼亚州州长招募？科学、数学和技术学院。

CBET -0853674 Devenport, William J. This research program aims to reveal and better understand the fluctuating surface pressure field produced by high Reynolds number rough-wall boundary layers. This pressure field is a source of vibration and noise in many applications. It also provides a measure of the turbulence structure of the boundary layer weighted in favor of the near-wall dynamics. However, there have been remarkably few prior studies of rough-wall boundary-layer pressure fluctuations. Studies have included only a limited set of rough surfaces and there has been little systematic examination of the effects of roughness type or sparseness. Most importantly, there have been almost no measurements of boundary layers with Reynolds number and boundary-layer-to-roughness scale ratios large enough to be free of transitional effects, where universal scalings and behaviors are likely to be observed and are of the most practical and scientific value. The objectives of this study are as follows: to extend the existing database of fluctuating pressure measurements for rough wall boundary layers into the high Reynolds number regime; to extend the database to include stochastic and deterministic surfaces with fully defined geometry and a significant range of sizes and sparseness values; to use these data to establish the low and high-frequency scaling of the rough wall pressure spectrum and the behavior of the convection velocities and the spatial pressure coherence functions; and to provide a cutting-edge research education to a diverse group of students including graduate, undergraduate and high-school students. The PI's experimental approach centers on the new aeroacoustic capabilities provided by the Virginia Tech Stability Wind Tunnel. This facility is both large and acoustically quiet and thus is uniquely suited to pressure fluctuation measurements and the growth of thick, fully developed, high-Reynolds number turbulent boundary layers with smooth or rough walls. A complete program of experiments on high Reynolds number flows over stochastic and deterministic rough surfaces will be performed to directly address the deficiencies in current knowledge. In many situations, such as with wind turbines or aircraft, the noise and vibration are a direct consequence of the fluctuating pressure field of a rough wall turbulent boundary layer. The improved understanding generated by this research will have a direct impact on the accuracy of noise source predictions. This is critical to advancing the environmental acceptability and economic viability of these devices. The Virginia Tech Stability Tunnel is a multi-user facility that draws a wide variety of users including research groups, commercial testing and a range of undergraduate classes. The planned work includes two specific sub-projects to be conducted by groups of undergraduate and high school students. These groups will be mentored by the graduate students involved in the project under the guidance of the PI. This continues a long history of undergraduate involvement in the PI's research group. High school students will be recruited through existing programs with the Southwest Virginia Governor?s School for Science, Mathematics and Technology.