68th Annual Meeting of the APS Division of Fluid Dynamics (November 22, 2015 — November 24, 2015)

V0015: Lagrangian coherent structures in the flow field of a fluidic oscillator

Authors

• Moritz Sieber, Chair of Fluid Dynamics, Hermann-Föttinger-Institut, Technische Universität Berlin, Berlin, Germany
• Florian Ostermann, Chair of Fluid Dynamics, Hermann-Föttinger-Institut, Technische Universität Berlin, Berlin, Germany
• Rene Woszidlo, The Boeing Company, Boeing Research and Technology, St. Louis, USA
• Kilian Oberleithner, Chair of Fluid Dynamics, Hermann-Föttinger-Institut, Technische Universität Berlin, Berlin, Germany
• C. Oliver Paschereit, Chair of Fluid Dynamics, Hermann-Föttinger-Institut, Technische Universität Berlin, Berlin, Germany

DOI: https://doi.org/10.1103/APS.DFD.2015.GFM.V0015

The internal flow of a fluidic oscillator together with its sweeping jet in the external flow field is captured by particle image velocimetry. The entire flow field is composed from several measurement domains concatenated to a global picture. The oscillatory motion in the individual measurements is inferred from simultaneous pressure measurements. This allows for the construction of a time-resolved flow field of the periodic motion in the internal and external flow. This composite data set enabls the calculation of Lagrangian coherent structures (LCS) by means of finite time Lyapunov exponents. The representation of the flow with LCS provides an intuitive comprehension of the complex dynamics in this flow. The switching mechanism in the internal flow as well as the mixing in the external flow can easily be deduced from this representation. Beside the scientific insight, the animated periodic motion of the flow has a high artistic value. It emphasizes the pure beauty of fluid dynamics phenomena through the combination of state-of-the-art measurement techniques and data processing.