The locations of Lagrangian saddles, identified as non-parallel intersections of positive and negative-time finite-time Lyapunov exponent (FTLE) ridges, have been shown to indicate the timing of von Kármán vortex shedding in the wake of bluff bodies. The Lagrangian saddles are difficult to track in real-time however, since future flow field data is needed for the computation of the FTLE fields. In order to detect the topological changes in the wake without direct access to the FTLE field, the saddle dynamics are related to measurable surface quantities on a circular cylinder in cross-flow. The Lagrangian saddle found upstream of a forming and subsequently shedding vortex has been shown to accelerate away from the cylinder surface as the vortex sheds. In previous numerical results for a two-dimensional flow at Re = 150, this acceleration coincides with a minimum in the static pressure at a location slightly upstream of the mean separation location. In the current work, this result is compared with results from three-dimensional numerical data at Re = 400, as well as two-dimensional experimental data at Re = 19, 000, with similar findings for each case. This successful validation provides a strategy for locating sensitive regions on the cylinder surface where vortex shedding could be detected using simple pressure transducers.
|Original language||English (US)|
|Title of host publication||47th AIAA Fluid Dynamics Conference, 2017|
|Publisher||American Institute of Aeronautics and Astronautics Inc, AIAA|
|State||Published - 2017|
|Event||47th AIAA Fluid Dynamics Conference, 2017 - Denver, United States|
Duration: Jun 5 2017 → Jun 9 2017
|Name||47th AIAA Fluid Dynamics Conference, 2017|
|Other||47th AIAA Fluid Dynamics Conference, 2017|
|Period||6/5/17 → 6/9/17|
Bibliographical noteFunding Information:
The authors would like to thank Yiyang Sun, Robert Reger, Kunihiko Taira, and Lou Cattafesta from Florida State University for sharing their numerical results. The authors are especially indebted to Yiyang Sun for her work in the preparation and analysis of the three-dimensional cylinder dataset. This work was supported by the Air Force Office of Scientific Research under AFOSR Award No. FA9550-14-1-0210.
© 2017, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.