Vortex Core Dynamics in a Swirling Jet Near Vortex Breakdown

Clees, Sean; Lewalle, Jacques; Frederick, Mark; O’Connor, Jacqueline

doi:10.2514/6.2018-0052

Cited by 3 publications

(5 citation statements)

References 42 publications

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“…However, the spatial variation ofŪ r (figure 9c) is not perfectly anti-symmetric about r = 0, as one may expect. This is because the presence of turbulence in the flow along with intermittent vortex breakdown observed for this case, both of which cause the rotational axis of the flow to 'wobble' incoherently about the geometric jet centreline; details of this process are described in Clees et al (2018). Ideally, given a long enough time record, one can expect that the impact of these incoherent flow centreline oscillations would average out, yielding an axisymmetricŪ r field (Syred, O'Doherty & Froud 1994).…”

Section: Linear and Leading-order Nonlinear Solutionsmentioning

confidence: 94%

“…At each swirl number, the flow is defined by a certain state; pre-vortex breakdown, near-vortex breakdown, steady vortex breakdown, weak PVC and strong PVC (Clees et al. 2018). Pre-vortex breakdown swirling jets correspond to , before a central recirculation zone forms.…”

Section: Flow Field Characterizationmentioning

confidence: 99%

“…The expression in (4.1) can be derived from the momentum flux based definition of swirl number (Beér & Chigier 1972) by assuming an axial inflow into an annulus with inner and outer radii, R c and R b , respectively, undergoing a deflection through and angle α as it passes through the swirl vanes. At each swirl number, the flow is defined by a certain state; pre-vortex breakdown, near-vortex breakdown, steady vortex breakdown, weak PVC and strong PVC (Clees et al 2018). Pre-vortex breakdown swirling jets correspond to 0 S 0.38, before a central recirculation zone forms.…”

Section: Flow Field Characterizationmentioning

confidence: 99%

“…We apply the weakly nonlinear theory derived in this paper to understand the emergence of PVC oscillations in a constant mass flow rate, variable swirl jet experiment at (based on the jet diameter and bulk flow velocity) (Clees et al. 2018; Frederick et al. 2018).…”

Section: Introductionmentioning

confidence: 99%

“…We apply the weakly nonlinear theory derived in this paper to understand the emergence of PVC oscillations in a constant mass flow rate, variable swirl jet experiment at Re = 59 000 (based on the jet diameter and bulk flow velocity) (Clees et al 2018;Frederick et al 2018). Time-resolved velocity field measurements are obtained using stereoscopic particle image velocimetry (sPIV) over a range of swirl numbers.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

A weakly nonlinear analysis of the precessing vortex core oscillation in a variable swirl turbulent round jet

et al. 2019

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Section: Linear and Leading-order Nonlinear Solutionsmentioning

confidence: 94%

Section: Flow Field Characterizationmentioning

confidence: 99%

Section: Flow Field Characterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A weakly nonlinear analysis of the precessing vortex core oscillation in a variable swirl turbulent round jet

et al. 2019

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A Quick Review on Experimental, Computational, and Optimization Studies of Coherent Structures in Swirling Flow

Patel,

Sharma

2024

Lecture Notes in Mechanical Engineering

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The Effects of Exit Boundary Condition on Precessing Vortex Core Dynamics

Mason

Clees

Frederick

et al. 2019

Volume 4B: Combustion, Fuels, and Emissions

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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.

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Vortex Core Dynamics in a Swirling Jet Near Vortex Breakdown

Cited by 3 publications

References 42 publications

A weakly nonlinear analysis of the precessing vortex core oscillation in a variable swirl turbulent round jet

A weakly nonlinear analysis of the precessing vortex core oscillation in a variable swirl turbulent round jet

A Quick Review on Experimental, Computational, and Optimization Studies of Coherent Structures in Swirling Flow

The Effects of Exit Boundary Condition on Precessing Vortex Core Dynamics

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