Title :
A theoretical approach to the passive control of spiral vortex breakdown
Author :
Qadri, Ubaid A. ; Juniper, Matthew P.
Author_Institution :
Dept. of Eng., Univ. of Cambridge, Cambridge, UK
Abstract :
Previous numerical simulations have shown that vortex breakdown starts with the formation of a steady axisymmetric bubble and that an unsteady spiralling mode then develops on top of this.We study how this spiral mode of vortex breakdown might be suppressed or promoted. We use a Lagrangian approach to identify regions of the flow which are sensitive to small open-loop steady and unsteady (harmonic) forces. We find these regions to be upstream of the vortex breakdown bubble. We investigate passive control using a small axisymmetric control ring. In this case, the steady and unsteady control forces are caused by the drag force on the control ring. We find a narrow region upstream of the bubble where the control ring will stabilise the flow and we verify this using numerical simulations.
Keywords :
bubbles; drag; flow control; flow instability; flow simulation; numerical analysis; open loop systems; two-phase flow; vortices; Lagrangian approach; narrow region upstream; numerical simulations; passive control; small axisymmetric control ring; small open-loop steady control forces; small open-loop unsteady control forces; spiral vortex breakdown; steady axisymmetric bubble; unsteady spiralling mode; Eigenvalues and eigenfunctions; Electric breakdown; Equations; Force; Mathematical model; Sensitivity; Spirals; adjoint; flow control; passive control; sensitivity analysis; vortex breakdown;
Conference_Titel :
Control (CONTROL), 2012 UKACC International Conference on
Conference_Location :
Cardiff
Print_ISBN :
978-1-4673-1559-3
Electronic_ISBN :
978-1-4673-1558-6
DOI :
10.1109/CONTROL.2012.6334707
