An active feedback flow control theory of the vortex breakdown process
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Authors
Granata, Joshua
Issue Date
2014-08
Type
Electronic thesis
Thesis
Thesis
Language
ENG
Keywords
Aerospace engineering
Alternative Title
Abstract
Computed examples of the flow dynamics based on the full Euler and Navier-Stokes formulations at various swirl levels demonstrate the evolution to near-steady breakdown states when swirl is above a critical level which depends on Re. Numerical stability and mesh convergence studies performed on the inviscid and high-Re flow simulations ensure the accuracy of the computations and the agreement with the theoretical approaches. In addition, an energy analysis of the nonlinear model problem sheds insight into the mechanisms of the flow dynamics which lead to vortex breakdown and suggests a feedback control law which relates the flow injection and the evolving maximum radial velocity at the inlet. Moreover, applying the proposed feedback control law during flow evolution, shows for the first time the successful and robust elimination of the breakdown states and flow stabilization on an almost columnar state for a wide range of swirl up to 53 percent above the first critical level for the inviscid flow case and for a range of swirl up to 15 percent above the first critical level for viscous flows. The control law can be improved for a lower momentary maximum flux injection through the use of discrete injection regions along the pipe. The feedback control cuts the natural feed-forward mechanism of the breakdown process. Specifically, in the case of high-Re flows, the control approach establishes a branch of columnar states for all swirl levels studied where in the natural flow dynamics no such states exist.
Description
August 2014
School of Engineering
School of Engineering
Full Citation
Publisher
Rensselaer Polytechnic Institute, Troy, NY