Numerical study of hysteresis in annular swirling jets with a stepped‐conical nozzle

Vanierschot, Maarten; Bulck, Eric Van den

doi:10.1002/fld.1400

Cited by 19 publications

(17 citation statements)

References 21 publications

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“…Although the decrease in density that occurred as the consequence of higher temperature affected the swirl number [1], it was noticed that the same transition happened at | X|/D=0.082 with α=45°using the same Re numbers. This phenomenon of superimposition was previously observed by Vanoverberghe [10,31]. As the high temperatures of the Coanda flame posed a threat to the Stereo PIV cameras and the flowrates were going to be kept at the same values, it was decided to shift experiments to isothermal conditions.…”

Section: Isothermal Experimentsmentioning

confidence: 52%

“…Mullyadzhanov et al [30] presents a coherent literature review of the topic with LES results showing the hysteresis of the transition phenomenon with some conclusions on the differences between hot and cold regimes. Vanierschot and Van den Bulck [31,32] describe different flow patterns produced by these configurations emphasizing some of the features during the transition process. They focus on the hysteresis of the phenomenon.…”

Section: Introductionmentioning

confidence: 99%

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Hydrodynamics During the Transient Evolution of Open Jet Flows from/to Wall Attached Jets

Valera‐Medina

Baej

2016

Flow Turbulence Combust

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Swirl stabilized flows are the most widely deployed technology used to stabilize gas turbine combustion systems. However, there are some coherent structures that appear in these flows close to the nozzle whose occurrence and stability are still poorly understood during transition. The external recirculation zone and the Precessing Vortex Core to/from the Coanda effect are some of them. Thus, in this paper the transition of an Open Jet FlowMedium Swirl flow pattern to/from a Coanda jet flow is studied using various geometries at a fixed Swirl number. Phase Locked Stereo Particle Image Velocimetry and High Speed Photography experiments were conducted to determine fundamental characteristics of the phenomenon. It was observed that the coherent structures in the field experience a complete annihilation during transition, with no dependency between the structures formed in each of the flow states. Moreover, transition occurs at a particular normalized step size whilst some acoustic shifts in the frequencies of the system were noticed, a phenomenon related to the strength of the vortical structures and vortices convection. It is concluded that a transient, precessing, Coanda Vortex Breakdown is formed, changing flow dynamics. The structure progresses to a less coherent Trapped Vortex between the two states. During the phenomenon there are different interactions between structures such as the Central Recirculation Zone, the High Momentum Flow Region and the Precessing Vortex Core that were also documented.

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Section: Isothermal Experimentsmentioning

confidence: 52%

Section: Introductionmentioning

confidence: 99%

Hydrodynamics During the Transient Evolution of Open Jet Flows from/to Wall Attached Jets

Valera‐Medina

Baej

2016

Flow Turbulence Combust

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“…The hysteresis in a swirl cycle was observed experimentally; also a numerical study by Vanierschot and Van den Bulck [5] could predict the four different flow patterns and their hysteretic behavior. Figure 2 shows a comparison between their numerical simulations and experimental data in a swirl cycle.…”

Section: Introductionmentioning

confidence: 94%

“…The nozzle is followed by a sudden expansion into a large confinement of diameter 30D o . The confinement is chosen large enough to simulate a free jet, and simulations with different confinement geometries show that the wall of the confinement has no influence on the velocity, pressure and turbulence profiles near the nozzle [5]. The outlet is chosen to be at 32.5D o .…”

Section: Turbulence Closurementioning

confidence: 99%

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Computation of a drastic flow pattern change in an annular swirling jet caused by a small decrease in inlet swirl

Vanierschot

Bulck

2008

Numerical Methods in Fluids

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SUMMARYThis paper investigates the flow pattern change in an annular jet caused by a sudden change in the level of inlet swirl. The jet geometry consists of an annular channel followed by a specially designed stepped-conical nozzle, which allows the existence of four different flow patterns as a function of the inlet swirl number. This paper reports on the transition between two of them, called the 'open jet flow high swirl' and the 'Coanda jet flow.' It is shown that a small sudden decrease of 4% in inlet swirl results in a drastic and irreversible change in flow pattern. The objective of this paper is to reveal the underlying physical mechanisms in this transition by means of numerical simulations. The flow is simulated using the unsteady Reynolds-averaged Navier-Stokes (URANS) approach for incompressible flow with a Reynolds stress turbulence model. The analysis of the numerical results is based on a study of different forces on a control volume, which consists of the jet boundaries. The analysis of these forces shows that the flow pattern change consists of three different regimes: an immediate response regime, a quasi-static regime and a Coanda regime. The simulation reveals that the pressure-tangential velocity coupling during the quasistatic regime and the Coanda effect at the nozzle outlet during the Coanda regime are the driving forces behind the flow pattern change. These physical mechanisms are validated with time-resolved stereo-PIV measurements, which confirm the numerical simulations.

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Numerical Investigation of Flow Near a Round Exhaust Channel Screened by an Annular Swirled Jet

Gritskevich

Logachev

2019

J Eng Phys Thermophy

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Numerical study of hysteresis in annular swirling jets with a stepped‐conical nozzle

Cited by 19 publications

References 21 publications

Hydrodynamics During the Transient Evolution of Open Jet Flows from/to Wall Attached Jets

Hydrodynamics During the Transient Evolution of Open Jet Flows from/to Wall Attached Jets

Computation of a drastic flow pattern change in an annular swirling jet caused by a small decrease in inlet swirl

Numerical Investigation of Flow Near a Round Exhaust Channel Screened by an Annular Swirled Jet

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