Analysis of the transition process around laminar separation bubbles (LSB‘s) in a towing tank using time-resolved 3D particle tracking techniques

使用时间分辨 3D 粒子跟踪技术分析拖曳池中层流分离气泡 (LSBâs) 周围的转变过程

• 批准号: 422177304
• 负责人: Professor Dr. Christian Joachim Kähler
• 金额: --
• 依托单位: Institut für Strömungsmechanik und Aerodynamik (LRT-7)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/422177304?language=en
• 关键词: Analysis; transition; process; around; laminar

The performance of various lifting surfaces at relatively low Reynolds numbers is known to be affected significantly by laminar boundary layer separation. The examples of the relevant application range from man-made systems, such as turbofan engine blades and tail surfaces on commercial aircraft, wind turbine blades, as well as to nature’s flyers and swimmers. The laminar boundary layer separation typically takes place on the suction side of the airfoil and leads to the formation of a separated shear layer. The flow can then undergo rapid transition and be reattached to the airfoil surface in the mean sense forming a Laminar Separation Bubble (LSB). As LSB’s alter the circulation of the airfoil and consequently the lift and drag, the overall flow development therefore depends on the formation and dynamics of the LSB, which are the main focal points of the present proposal. Despite a significant research progress made to date towards understanding LSB dynamics, a number of critical gaps in knowledge of both fundamental importance remain to be addressed, which serves as a motivation for the present proposal. As the free stream turbulence level has a significant effect on the formation of LSB and the transition process, the experiments will be performed in a towing channel whose free stream turbulence can be varied between zero and two percent. Furthermore, sophisticated three-dimensional time-resolved flow measurement techniques will be used to resolve all flow processes in space and time with high special resolution and low measurement uncertainty. It is expected that the studies will significantly improve the current state of knowledge and that open research questions can be reliably answered.

众所周知，在较低雷诺数下，各种升力面的性能受层流附面层分离的影响很大。相关应用的例子包括人造系统，如商用飞机上的涡轮风扇发动机叶片和尾翼、风力涡轮机叶片，以及自然界的飞行者和游泳者。层流边界层分离通常发生在翼型的吸力侧，并导致形成分离的剪切层。然后，气流可以经历快速过渡，并重新附着到翼型表面，形成层流分离泡（LSB）。由于LSB会改变翼型的环流，从而改变升力和阻力，因此，总体流动发展取决于LSB的形成和动力学，这是本提案的主要焦点。尽管迄今为止在理解LSB动力学方面取得了重大的研究进展，但仍有一些具有根本重要性的知识方面的关键差距有待解决，这是本提案的动机。由于自由流湍流度对LSB的形成和转捩过程有显着影响，因此实验将在自由流湍流度可在零到百分之二之间变化的拖曳通道中进行。此外，先进的三维时间分辨流量测量技术将被用来解决所有的流动过程中的空间和时间，具有高的特殊分辨率和低的测量不确定性。预计这些研究将大大改善目前的知识状况，并可以可靠地回答开放的研究问题。