Control of vortex breakdown in a closed cylinder with a small rotating rod

Jacono, David Lo; Sørensen, Jens Nørkær; Thompson, Mark C.; Hourigan, Kerry

doi:10.1016/j.jfluidstructs.2008.06.015

Cited by 18 publications

(8 citation statements)

References 13 publications

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“…VB suppression is an active area of research with application, for example, to delta wing aircraft. A number of suppression methods have been proposed, including blowing at the vortex cen ter with corotating cool jets [38], and rotating rods at the vortex center [39]. The former technique can be used to increase the total pressure at the vortex axis to reduce the adverse axial pressure gradients.…”

Section: Design Challengesmentioning

confidence: 99%

Design of a Nonreacting Combustor Simulator With Swirl and Temperature Distortion With Experimental Validation

Hall

Chana

Povey

2014

Journal of Engineering for Gas Turbines and Power

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Nonuniform combustor outlet flows have been demonstrated to have significant impact on the first and second stage turbine aerothermal performance. Rich-burn combustors, which generally have pronounced temperature profiles and weak swirl profiles, primarily affect the heat load in the vane but both the heat load and aerodynamics of the rotor. Lean burn combustors, in contrast, generally have a strong swirl profile which has an additional significant impact on the vane aerodynamics which should be accounted for in the design process. There has been a move towards lean burn combustor designs to reduce NOx emissions. There is also increasing interest in fully integrated design proc esses which consider the impact of the combustor flow on the design of the high pressure vane and rotor aerodynamics and cooling. There are a number of current large research projects in scaled (low temperature and pressure) turbine facilities which aim to provide validation data and physical understanding to support this design philosophy. There is a small body of literature devoted to rich burn combustor simulator design but no open lit erature on the topic of lean burn simulator design. The particular problem is that in non reacting, highly swirling and diffusing flows, vortex instability in the form of a precessing vortex core or vortex breakdown is unlikely to be well matched to the reacting case. In reacting combustors the flow is stabilized by heat release, but in low temperature simula tors other methods for stabilizing the flow must be employed. Unsteady Reynoldsaveraged Navier-Stokes and large eddy simulation have shown promise in modeling swirling flows with unstable features. These design issues form the subject of this paper.

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Section: Design Challengesmentioning

confidence: 99%

Design of a Nonreacting Combustor Simulator With Swirl and Temperature Distortion With Experimental Validation

Hall

Chana

Povey

2014

Journal of Engineering for Gas Turbines and Power

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“…The code employed has been well proven for use in bluff-body problems, and Floquet stability analysis. 17,[32][33][34] However, a brief outline of the method is given. The base flows for the present study were calculated by solving the incompressible, timedependent Navier-Stokes equations.…”

Section: Numerical Formulationmentioning

confidence: 99%

The three-dimensional wake of a cylinder undergoing a combination of translational and rotational oscillation in a quiescent fluid

et al. 2009

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Previous two-dimensional numerical studies have shown that a circular cylinder undergoing both oscillatory rotational and translational motions can generate thrust so that it will actually self-propel through a stationary fluid. Although a cylinder undergoing a single oscillation has been thoroughly studied, the combination of the two oscillations has not received much attention until now. The current research reported here extends the numerical study of Blackburn et al. ͓Phys. Fluids 11, L4 ͑1999͔͒ both experimentally and numerically, recording detailed vorticity fields in the wake and using these to elucidate the underlying physics, examining the three-dimensional wake development experimentally, and determining the three-dimensional stability of the wake through Floquet stability analysis. Experiments conducted in the laboratory are presented for a given parameter range, confirming the early results from Blackburn et al. ͓Phys. Fluids 11, L4 ͑1999͔͒. In particular, we confirm the thrust generation ability of a circular cylinder undergoing combined oscillatory motions. Importantly, we also find that the wake undergoes three-dimensional transition at low Reynolds numbers ͑ReӍ 100͒ to an instability mode with a wavelength of about two cylinder diameters. The stability analysis indicates that the base flow is also unstable to another mode at slightly higher Reynolds numbers, broadly analogous to the three-dimensional wake transition mode for a circular cylinder, despite the distinct differences in wake/mode topology. The stability of these flows was confirmed by experimental measurements.

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“…14,15 The code employed has been well proven for use in bluff-body problems. [16][17][18] The timeasymptotic wake flows for the present study were calculated by solving the incompressible, time-dependent NavierStokes equations in a translating accelerating frame of reference attached to the cylinder. The discretization method employed was a spectral-element method using seventh-order Lagrange polynomials associated with Gauss-LobattoLegendre quadrature points.…”

mentioning

confidence: 99%

Flow behind a cylinder forced by a combination of oscillatory translational and rotational motions

et al. 2009

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The flow behind a cylinder undergoing forced combined oscillatory motion has been studied. The motion consists of two independent oscillations: cross-stream translation and rotation. Previous studies have extensively investigated the effect of these motions individually on cylinder wakes; however, the investigation of their combined effect is new. The motivation lies in its application to vortex-induced vibration and its suppression and to biomimetic motion. The focus is on the effect of the phase difference between the two motions. The results show that there is an unexpected loss of synchronization of the wake for a finite range of phase differences.The primary goal of this research is to understand the physical mechanisms behind the response of a cylinder wake to the combined forcing mechanisms of cross-stream translation and rotational oscillations. With an in-depth understanding of the flow physics it may be possible to propose a novel means of actively or passively suppressing the lock-on between vortex shedding and transverse oscillation. Also, we are interested in the application to biomimetic motions and, in particular, to carangiform motion. 1 There has been considerable research on the effect of either transverse or rotational oscillations on cylinder wakes, as discussed in the extensive reviews. 2,3 Primarily, these have focused on the translational oscillation due to their focus on vortex-induced vibration. There have also been studies of the effect of rotational oscillation on wakes. 4,5 Previous numerical work has also been performed on the effect of the combined motions in quiescent fluids 6 and when there is a flow past the cylinder; 7 however, the influence of an important parameter was not considered. Indeed, previous interesting results 6,8 indicate that the phase difference between the two motions is of considerable importance and this is the focus of the research discussed here. This work is part of a more extensive set of experiments that considers the full range of independent variables.The experiments were conducted in the FLAIR freesurface closed-loop water channel at Monash University. A schematic of the problem is given in Fig. 1. The cylinder used was 800 mm in length and with an outer diameter of D = 20 mm, giving an aspect ratio of 40. The experiments were performed for a fixed upstream velocity U ϱ = 0.0606 m / s giving Re= U ϱ D / = 1322. Two sinusoidal motions were imposed, namely, translational ͑cross stream͒, given by y͑t͒ = A t sin͑2f t t͒ / D, and rotational, given by ͑t͒ = A sin͑2f t + ⌽͒. The frequencies are fixed close to that of the natural frequency ͑T −1 = f t = f = 0.6 s −1 Ϸ f N ͒. The natural frequency was found to be equal to f N Ϸ 0.6154 s −1 .The Strouhal number based on this frequency is about St Ϸ f N D / U ϱ = 0.203 and the Strouhal number of the forcing is St t Ϸ f t D / U ϱ = 0.198. The experiments presented are for fixed amplitudes of oscillation, A t = D / 2 and A = 1. These amplitudes combined with the equal frequencies provide equal maximum velocities fro...

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Control of vortex breakdown in a closed cylinder with a small rotating rod

Cited by 18 publications

References 13 publications

Design of a Nonreacting Combustor Simulator With Swirl and Temperature Distortion With Experimental Validation

Design of a Nonreacting Combustor Simulator With Swirl and Temperature Distortion With Experimental Validation

The three-dimensional wake of a cylinder undergoing a combination of translational and rotational oscillation in a quiescent fluid

Flow behind a cylinder forced by a combination of oscillatory translational and rotational motions

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