U.S.-Netherlands Cooperative Research on the Structure of a Turbulent Boundary Layer with Suction

该奖项支持乔治亚理工学院的助理教授Minami Yoda与荷兰代尔夫特理工大学航空与流体动力学实验室的F.T.M. Nieuwstadt教授在机械工程研究方面的合作。利用粒子成像测速技术，他们将在几个直径为当地边界层厚度10%的孔附近，对有吸力和没有吸力的湍流边界层进行研究。荷兰实验室为这项研究提供了优秀的实验设施，美国PI将获得的经验将为决定是否以及如何在佐治亚理工学院建立类似的设施提供基础。这两个实验室为研究工作带来了水动力系统和专业仪器方面的互补专业知识：Delft在有界流动中的应用以及粒子成像测速和佐治亚理工学院在自由剪切流动控制和激光诱导荧光中的应用。湍流增加了飞机机翼等移动表面的阻力（和运行成本）。众所周知，吸力会使湍流边界层重新分层并延迟分离，但过大的吸力实际上会增加分离。通过大孔或大槽的吸力已被广泛研究；漏洞越小效果越好，但人们发现，实施的成本并不值得拖延。虽然新技术现在可以经济地生产微小穿孔表面，但相对而言，人们对吸力对边界层结构上这种小孔的影响知之甚少。这项工作将有助于澄清这种吸力如何影响边界层中的相干结构，并增加对“气动粗糙度”的理解，在这种情况下，强吸力水平实际上会导致分离。

This award supports Assistant Professor Minami Yoda of Georgia Institute of Technology to collaborate in mechanical engineering research with Professor F.T.M. Nieuwstadt of the Laboratory of Aeroand Hydrodynamics of the Delft University of Technology, The Netherlands. Using particle imaging velocimetry, they will carry out a study of a turbulent boundary layer with and without suction in the vicinity of a few holes of a diameter of ten percent of the local boundary layer thickness. The Dutch laboratory has excellent experimental facilities for this research, and the experience with their set-up to be gained by the US PI will provide the basis for deciding whether and how to establish similar facilities at Georgia Tech. The two laboratories bring to the research effort complementary expertise in both hydrodynamic systems and specialized instrumentation: Delft in bounded flows and the application of particle imaging velocimetry and Georgia Tech in free shear flow control and laser-induced fluorescence. Turbulence increases drag (and operating cost) on moving surfaces such as airplane wings. Suction is known to re- laminarize and delay the separation of turbulent boundary layers, but too much suction can actually increase the separation. Suction through large holes or slots has been widely studied; smaller holes work better, but the cost of implementing has been found not to be worth the savings in drag. While new technology now permits economical production of minutely perforated surfaces, relatively little is known about the effect of suction on such small holes on the boundary layer structure. This work will help to clarify how such suction affects the coherent structures in the boundary layers, and increase understanding of `aerodynamic roughness`, where strong suction levels actually cause separation.