Sweeping Jet from a Fluidic Oscillator in Crossflow

Описание: Sweeping Jet from a Fluidic Oscillator in Crossflow

Florian Ostermann, Hermann-Föttinger-Institut, Technische Universität Berlin, Berlin, Germany
Philipp Godbersen, Hermann-Föttinger-Institut, Technische Universität Berlin, Berlin, Germany
Rene Woszidlo, Hermann-Föttinger-Institut, Technische Universität Berlin, Berlin, Germany
C. Navid Nayeri, Hermann-Föttinger-Institut, Technische Universität Berlin, Berlin, Germany
C. Oliver Paschereit, Hermann-Föttinger-Institut, Technische Universität Berlin, Berlin, Germany

DOI: https://doi.org/10.1103/APS.DFD.2016....

The presented video illustrates the experimentally acquired time-resolved flow field of a spatially oscillating jet in crossflow. The jet’s oscillation plane is perpendicular to the cross flow over a flat plate. The ratio between jet velocity and freestream is three and the oscillation frequency is 67 Hz. A traversable stereoscopic Particle Image Velocimetry system is employed to acquire velocity information. The time-resolved, three-dimensional flow field is constructed from individual planes. A simultaneously acquired reference signal inside the oscillator is used to phase-average and phase-align the individual planes. Initially, the video illustrates the velocity magnitude which demonstrates the spatial oscillation of the jet. More details are revealed by the streak volume of particles originating from the jet. Two alternating, streamwise vortices are formed by the jet when interacting with the crossflow. Their sense of rotation is opposite to the counter-rotating vortex pair of a steady jet in crossflow. Therefore, the vortices provide a downwash in between them. This behavior may be one of the driving mechanisms behind the high efficacy of spatially oscillating jets in separation control. Finally, the finite-time Lyapunov exponent is visualized which considers not only the particles originating from the jet but also from the freestream.

See other videos from the 2015 Gallery of Fluid Motion: http://gfm.aps.org/