Transition of A Vortex Ring Visualized by 3D Scanning TomoPIV

Sun, Z., Bruecker, C. & Pointz, B. (2016). Transition of A Vortex Ring Visualized by 3D Scanning TomoPIV. Paper presented at the 18th International Symposium on Applications of Laser Techniques to Fluid Mechanics, 4-7 Jul 2016, Lisbon, Portugal.

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Abstract

A vortex ring with piston-based Reynolds number Rep=4650 is studied experimentally by means of time-resolved scanning tomographic PIV. The present measurement technique provides the so-called 4D flow field, thus enables revealing the vortex ring’s transition from laminar to turbulent. The evolution of the ring torus as well as the generation of secondary vortex filaments in transition are first observed through 3D visualization. Analysis on the quantities of the vortex ring, such as circulation and vorticity components, defines the three evolution phases, namely laminar, transition and turbulent. The ring median plane is also examined to provide further insights on flow structure exhibited in transition. The axial vorticity component and radial velocity component are studied respectively and they are found to be organized in a multi-layer concentric-ring pattern. Spectrum analysis on the radial velocity component along the ring core and inner ring where secondary vortical activity happens reveals the dominate wavenumber in transition and broad band of wavenumbers in turbulent phase.

Item Type: Conference or Workshop Item (Paper)
Uncontrolled Keywords: Vortex ring, Tomographic PIV,Scanning PIV
Subjects: T Technology > TJ Mechanical engineering and machinery
Divisions: School of Engineering & Mathematical Sciences > Engineering
URI: http://openaccess.city.ac.uk/id/eprint/15664

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