Inhalt des Dokuments
Gallery of Fluid Motion Award
Lagrangian coherent structures in the flow field of a fluidic oscillator
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.