Observations of the Oscillatory Behavior of a Confined Ring Vortex

Escudier, M. P.; Merkli, P.

doi:10.2514/3.61109

Cited by 8 publications

(4 citation statements)

References 5 publications

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“…The cyclone separator, vortex whistle, fluidic vortex valve, Ranque-Hilsch tube, swirl combustor and gas-core nuclear rocket are among numerous practical devices the performance of which is dominated by a confined turbulent vortex created by tangential injection of all or part of the through-flow. The present authors' interest in confined-vortex flow is motivated by its importance with regard to the characteristics of the inlet and outlet chambers of conventional axial-flow turbomachines where, in contrast to the other applications mentioned, the presence of a vortex is largely fortuitous and leads to such undesirable characteristics as periodic flow oscillations and a circumferentially non-uniform distribution of pressure (Escudier & Merkli 1979; Merkli & Escudier 1979), as well as high pressure loss (Escudier 1979).…”

Section: Introductionmentioning

confidence: 99%

“…I n this paper we present LDA measurements, supported by flow visualization, of the mean axial-and swirl-velocity distributions for flow in a straight, jet-driven, vortex tube with the inlet slit running along its entire length (figure 1). The geometry of this model was developed from the ring-tube exit-chamber geometry, discussed in the recent paper by Escudier & Merkli (1979), in which some preliminary LDA measurements were made but which were discontinued in favour of the present investigation in view of the additional complexity of the flow in the ring, engendered in large part by Coriolis forces arising as ti result of the toroidal geometry. Our vortex-tube geometry is also close to that envisaged byN.A.S.A.…”

Section: Introductionmentioning

confidence: 99%

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Observations and LDA measurements of confined turbulent vortex flow

1980

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A series of LDA measurements and visual observations of confined turbulent vortex flow are described. The experiments were performed with water as the fluid medium in a vortex tube of length-to-diameter ratio L/D = 3.8 for a range of exit diameters De between De/D = 1 and 0.18. The experiments reveal a remarkable change in the vortex structure as De is reduced: from a thick core with an axial-velocity defect in the centre, and even reversed flow, to a thin annular jet-like core with a peak axial velocity more than an order of magnitude greater than the average value and again a central velocity deficit. The corresponding swirl profiles are not remarkable and are well-represented under all conditions by the solution of Burgers (1948), albeit with a velocity maximum which is strongly dependent upon De.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Observations and LDA measurements of confined turbulent vortex flow

1980

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“…The core size structure inside a vortex chamber has a wavy character, see Darmofal et al (2001). Meanwhile, the core shape based on LDV measurements of Escudier (1979), Escudier and Merkli (1979) confi rm that these variations are very small. In addition, the visualization experiments results of Lam (1993) and Alekseenko et al (1999) showed that the core of the vortex remains approximately the same throughout the chamber; the amplitude of the oscillations was found to be small in comparison with the size of the vortex core.…”

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confidence: 91%

Flow Characteristics in a Vortex Chamber

2008

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In this article we examine confined swirling flows using the integral equations of continuity and energy, along with the minimum pressure criterion. The pressure drop and the core size have been studied in the swirling confined vortex chamber. Both the n = 2 vortex model, with reverse and non‐reverse flow, and the free vortex model have been used at the vortex chamber exit plane. The influence of vortex chamber geometry, such as contraction ratio, inlet angle, area ratio, aspect ratio, and Reynolds number, on the flow field has been analyzed and compared with the present experimental data. The pressure drop across the vortex chamber differs from that in pipe flow, due to the mechanism of swirl flow that depends mainly on the intensity of tangential velocity. If the chamber length is increased, the vortex decays producing a weaker tangential velocity (less centrifugal force) that leads to less pressure drop. Based on the present theory, a new approach to determine the tangential velocity and radial pressure profiles inside the vortex chamber is developed and compared with the available experimental data. It shown that the n = 2 vortex model with reverse flow gives better results for strongly swirling flow.

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“…Early reports of this precessing vortex in swirling flow were given by Chanaud (1965), Cassidy and Falvery (1970) and Escudier and Merkli (1979), and visual observations showed flow reversal and a helical precessing vortex. Chanaud (1965) suggested that the precessing vortex derives its energy from the hydrodynamic instability of the flow and Syred and Be6r (1974) indicated that its core lies on the boundary of the mean reversed flow zone between the zero axial velocity and the zero streamline.…”

Section: Introductionmentioning

confidence: 99%

Downstream boundary effects on the spectral characteristics of a swirling flowfield

Chao

Leu

Hung

et al. 1991

Experiments in Fluids

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The spectral characteristics and the structural response of a swirling flowfield are investigated subject to a non-axisymmetric disturbance and a contraction imposed downstream. Two natural frequencies are noted in different regions of the undisturbed swirling flowfield, one is due to a precessing vortex core and the other to the most amplified downstream azimuthal instability. The downstream contraction usually causes compression of the central recirculation zone into two side-lobes, increases the dominant frequencies and forms a straight central vortex core with a high axial velocity. The dominant downstream instability frequency depends linearly on the inlet Reynolds number and on the mode of the breakdown. For the downstream non-axisymmetric disturbance, such as the passing of the turbine blades, the fundamental frequency is not altered by the disturbance and the oscillation strength of the downstream instability is greatly reduced as the excitation frequency remains unmatched with the dominant downstream natural frequency. Downstream azimuthal instability promotes the breakdown recirculation.

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Observations of the Oscillatory Behavior of a Confined Ring Vortex

Cited by 8 publications

References 5 publications

Observations and LDA measurements of confined turbulent vortex flow

Observations and LDA measurements of confined turbulent vortex flow

Flow Characteristics in a Vortex Chamber

Downstream boundary effects on the spectral characteristics of a swirling flowfield

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