The formation and shedding of vortices in two vortex-dominated flows around an actuated flat plate are studied to develop a better method of identifying and tracking coherent structures in unsteady flows. The work automatically processes data from the 2D simulation of a flat plate undergoing a 45∘ pitch-up maneuver, and from experimental particle image velocimetry data in the wake of a continuously pitching trapezoidal panel. The Eulerian Γ1, Γ2, and Q functions, as well as the Lagrangian finite-time Lyapunov exponent are applied to identify both the centers and boundaries of the vortices. The multiple vortices forming and shedding from the plates are visualized well by these techniques. Tracking of identifiable features, such as the Lagrangian saddle points, is shown to have potential to identify the timing and location of vortex formation, shedding, and destruction more precisely than by only studying the vortex cores as identified by the Eulerian techniques.
Bibliographical noteFunding Information:
Dr. Jeff Eldredge and his research group at UCLA are gratefully acknowledged for sharing the database of simulation results for the current research. This work was supported by the Air Force Office of Scientific Research under AFOSR Award No. FA9550-14-1-0210 and by the Office of Naval Research under ONR Award No. N00014-14-1-0418.
© 2015, Springer-Verlag Berlin Heidelberg.
- Finite-time Lyapunov exponent
- Unsteady aerodynamics
- Vortex detection