On the axisymmetric vortex breakdown of a swirling jet entering a sudden expansion pipe

2004 ◽  
Vol 16 (9) ◽  
pp. 3495-3498 ◽  
Author(s):  
Antonio Revuelta
Keyword(s):  
Vortex Breakdown ◽  
Sudden Expansion ◽  
Swirling Jet ◽  
Axisymmetric Vortex

Thermal effects on axisymmetric vortex breakdown in a spherical gap

1993 ◽  
Vol 5 (5) ◽  
pp. 1211-1223 ◽  
Author(s):  
A. Arkadyev ◽  
P. Bar‐Yoseph ◽  
A. Solan ◽  
K. G. Roesner
Keyword(s):  
Thermal Effects ◽  
Vortex Breakdown ◽  
Axisymmetric Vortex

Axisymmetric Vortex Breakdown in Rotating Fluid Within a Container

1982 ◽  
Vol 49 (4) ◽  
pp. 921-923 ◽  
Author(s):  
H. J. Lugt ◽  
H. J. Haussling
Keyword(s):  
Vortex Breakdown ◽  
Rotating Fluid ◽  
Axisymmetric Vortex

The Effects of Exit Boundary Condition on Precessing Vortex Core Dynamics

2019 ◽  
Author(s):  
Danielle Mason ◽  
Sean Clees ◽  
Mark Frederick ◽  
Jacqueline O’Connor
Keyword(s):  
Boundary Condition ◽  
Vortex Core ◽  
Gas Turbines ◽  
Vortex Breakdown ◽  
Base Flow ◽  
Eigenvalue Decomposition ◽  
Precessing Vortex Core ◽  
Swirling Jet ◽  
Exit Boundary ◽  
The Impact

Abstract Many industrial combustion systems, especially power generation gas turbines, use fuel-lean combustion to reduce NOx emissions. However, these systems are highly susceptible to combustion instability, the coupling between combustor acoustics and heat release rate oscillations of the flame. It has been shown in previous work by the authors that a precessing vortex core (PVC) can suppress shear layer receptivity to external perturbations, reducing the potential for thermoacoustic coupling. The goal of this study is to understand the effect of combustor exit boundary condition on the flow structure of a swirling jet to increase fundamental understanding of how combustor design impacts PVC dynamics. The swirling jet is generated with a radial-entry, variable-angle swirler, and a quartz cylinder is fixed on the dump plane for confinement. Combustor exit constriction plates of different diameters are used to determine the impact of exit boundary condition on the flow field. Particle image velocimetry (PIV) is used to capture the velocity field inside the combustor. Spectral proper orthogonal decomposition, a frequency-resolved eigenvalue decomposition that can identify energetic structures in the flow, is implemented to identify the PVC at each condition in both energy and frequency space. We find that exit boundary diameter affects both the structure of the flow and the dynamics of the PVC. Higher levels of constriction (smaller diameters) force the downstream stagnation point of the vortex breakdown bubble upstream, resulting in greater divergence of the swirling jet. Further, as the exit diameter decreases, the PVC becomes less energetic and less spatially defined. Despite these changes in the base flow and PVC coherence, the PVC frequency is not altered by the exit boundary constriction. These trends will help inform our understanding of the impact of boundary conditions on both static and dynamic flame stability.

An active feedback flow control theory of the axisymmetric vortex breakdown process

2015 ◽  
Vol 774 ◽  
pp. 488-528 ◽  
Author(s):  
Zvi Rusak ◽  
Joshua Granata ◽  
Shixiao Wang
Keyword(s):  
Feedback Control ◽  
Control Theory ◽  
Radial Velocity ◽  
Flow Injection ◽  
Vortex Breakdown ◽  
Flow Dynamics ◽  
Control Law ◽  
Breakdown Process ◽  
Axisymmetric Vortex ◽  
Active Feedback

An active feedback flow control theory of the axisymmetric vortex breakdown process in incompressible swirling flows in a finite-length straight circular pipe is developed. Flow injection distributed along the pipe wall is used as the controller. The flow is subjected to non-periodic inlet and outlet conditions where the inlet profiles of the axial velocity, circumferential velocity and azimuthal vorticity are prescribed, along with no radial velocity at the outlet. A long-wave asymptotic analysis at near-critical swirl ratios, which involves a rescaling of the axial distance and time, results in a model problem for the dynamics and the nonlinear control of both inviscid and high-Reynolds-number ($\mathit{Re}$) flows. The approach provides the bifurcation diagram of steady states and the stability characteristics of these states. In addition, an energy analysis of the controlled flow dynamics suggests a feedback control law that relates the flow injection to the evolving maximum radial velocity at the inlet. 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 that depends on $\mathit{Re}$. 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 at least 30 %) above critical. The feedback control cuts the natural feed-forward mechanism of the breakdown process. Specifically, in the case of high-$\mathit{Re}$ 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. The present theory is limited to the control of axisymmetric flows in pipes where the wall boundary layer is thin and attached and does not interact with the flow in the bulk.

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