Investigation of Acoustic and Hydrodynamic Modes in a Two/three-dimensional Incompressible Cavity Flow Using Wall-microphone Arrays

建议编号：CTS-0425374PRINCIPAL调查员：Ahmed NAGUIBINSTUTION：密歇根州立大学这笔赠款支持对二维和三维低马赫数空腔流动中的壁压和流动模式的研究。自我维持的振荡存在于各种各样的实际构型中，包括飞机和海军舰艇、汽车的开口(例如天窗)，甚至在水力学和土木工程领域。这项研究的一个独特特点是通过在战略上选择的位置使用大型传感器阵列来分辨率壁压模式的频率和波数。阵列测量将与使用粒子图像测速仪(PIV)的同步流场测量相耦合，通过基于多点壁面压力的随机估计来获得伪瞬时流动结构的时间分辨估计。实验中重点研究了两个关键的流动特性：(1)空腔底部壁面压力的波数-频谱及其相关弥散关系(对流速度与频率的关系)；(2)冲击唇部附近流动结构的三维特性。在第一年中，我们将研究各种腔体几何参数对这些特性的影响。第二年将研究分离边界层性质的影响，而第三年将致力于研究平均流三维的意义。该项目利用了几个现有的资源，这些资源已经得到了之前授予NSF的项目的支持。该项目的实施将导致一名博士生的培训。PI打算让一名本科生参与这项研究，希望她/他能被录取到研究生院。此外，密歇根州立大学的现有项目将在夏季将一名高中生纳入团队，向他/她展示研究和发现过程的兴奋。

PROPOSAL NO.: CTS-0425374PRINCIPAL INVESTIGATOR: AHMED NAGUIBINSTITUTION: MICHIGAN STATE UNIVERSITYThis grant supports a study of the wall-pressure and flow modes in a two- and three-dimensional low-Mach-number cavity flows. Self-sustained oscillations occur in a wide variety of practical configurations, including aircraft and naval vessels, openings in automobiles (e.g. sunroofs), and even in the field of hydraulics and civil engineering. A unique feature of the investigation is the resolution of both the frequency and wave number of the wall-pressure modes by employing large sensor arrays at strategically chosen locations. The array measurements will be coupled with simultaneous flow-field measurements using Particle Image Velocimetery (PIV) to obtain time-resolved estimation of the pseudo-instantaneous flow structure via multi-point wall-pressure-based stochastic estimation. Two key flow characteristics are emphasized in these experiments: (1) wave number-frequency spectra of the wall-pressure on the cavity bottom and associated dispersion relation (convection velocity versus frequency); (2) three-dimensionality of the flow structure in the vicinity of the impingement lip. The influence of various cavity geometrical parameters on these characteristics will be investigated during the first year. In the second year, effects of the separating boundary layer properties will be examined, while the third year will be dedicated to examining the significance of mean-flow three-dimensionality. The project capitalizes on several existing resources that have been enabled by a previously awarded NSF project. Execution of this project will result in the training of one Ph.D. student. The PI intends to involve an undergraduate student in the research, hopefully leading to her/his recruitment to graduate school. Moreover, existing programs at Michigan State University will be utilized to include a high-school student in the team during the summer, demonstrating to him/her the excitement of the process of research and discovery.