Hysteresis and turbulent vortex breakdown in transitional swirling jets

Moise, Pradeep; Mathew, Joseph

doi:10.1017/jfm.2021.118

Cited by 17 publications

(4 citation statements)

References 62 publications

(222 reference statements)

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“…For what concerns laminar-inflow configurations, a bubble-type VB characterizes the MPI-S140 case. In contrast, the high-swirl level imparted to the flow in the MPI-S200 case results in a regular conical VB, consistent with results of Moise and Mathew (2021). In both configurations, the vortex breakdown phenomenology leads to the onset of a stagnation point and the establishment of a central recirculation region downstream.…”

Section: Effect Of Swirl On the Jet Topologysupporting

confidence: 81%

“…Furthermore, a 10% axial coflow is imposed over the first 8 radii of the jet inflow section, i.e., U z,cof = 0.1U z,0 on the base of the cylindrical domain, to avoid the establishment of Coanda effect. In fact, the latter would cause the flow sheet issuing into the cylindrical domain to be attracted towards the inflow plane Moise and Mathew (2021), leading to a completely different jet topology.…”

Section: Turbulent-pipe Inflowmentioning

confidence: 99%

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Direct numerical simulation of Vortex Breakdown in Evaporating Dilute Sprays

Liberatori

Battista

Barba

et al. 2023

Preprint

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The effects of different vortex breakdown states on the evaporation process characterizing air-acetone vapor swirling jets laden with liquid acetone droplets in the dilute regime are discussed based on results provided by direct numerical simulations. Adopting the point-droplet approximation, the carrier phase is solved using an Eulerian framework, whereas a Lagrangian tracking of the dispersed phase is used. Three test cases are investigated: one with fully-turbulent pipe inflow conditions and two with a laminar Maxworthy velocity profile at different swirl rates. Consequently, turbulent, bubble-type and regular conical vortex breakdown states are established. Following phenomenological and statistical analyses of both phases, a significant enhancement of the overall droplet evaporation process due to the onset of the conical vortex breakdown is observed due to the strongest centrifugal forces driving the entire liquid drops towards the low-saturation mixing layer of the jet. The effects of droplet inertia on evaporation are isolated through an additional set of simulations where liquid droplets are treated as Lagrangian tracers. While it is found that inertial effects contribute to enhanced vaporization near the mixing layer under bubble vortex breakdown conditions, droplet inertia plays a secondary role under both turbulent and conical vortex breakdown due to intense turbulent mixing and high centrifugal forces, respectively.

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Section: Effect Of Swirl On the Jet Topologysupporting

confidence: 81%

Section: Turbulent-pipe Inflowmentioning

confidence: 99%

Direct numerical simulation of Vortex Breakdown in Evaporating Dilute Sprays

Liberatori

Battista

Barba

et al. 2023

Preprint

View full text Add to dashboard Cite

show abstract

“…[36][37][38][39] they found seven different types of vortex breakdown. In swirling flows, three forms were considered to be the more distinguished: bubble, spiral, and double helix types [36][37][38][39][40].…”

Section: Vortex Breakdown (Vb)mentioning

confidence: 99%

Flame Stability in Swirling and Bluff-Body Burners: A Review

Shakir Mahmood,

Saleh

2023

Jurnal Teknologi

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Flame stability is one of the main challenges facing the different combustion applications. A lot of undesirable phenomena such as blow-off and flashback may occur according to the instability of the flame causing damage to the overall combustion system. Therefore, it is necessary to develop methods which help improve the combustion process and obtain wider flame stable regions. Among these methods, swirling flows and bluff-bodies are the most commonly used in flame stabilization. These may create central recirculation zones (CRZ’s) that, in turn, recirculate the heat and active chemical species to the root of flame, improving the reactants mixing and as a result, flame stability. Hence, the current article presents an overview of flame stability mechanisms and the operation map using swirling flows and bluff-bodies. The effect of the swirl number (S) and burner’s geometry, as well as the influence of the bluff-body shape, size and position on the flame stabilization mechanisms are discussed.

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“…Benjamin (1962), Escudier (1988), Brown & Lopez (1990), Gelfgat, Bar-Yoseph & Solan (1996), Billant, Chomaz & Huerre (1998), Ruith et al. (2003), Moise & Mathew (2021), Shtern (2012) and references therein). So far, it has been observed in flows not affected (thus, not accelerated) by gravity, so their slow-down is less counter-intuitive – but it is still the same effect as the one described here.…”

Section: Introductionmentioning

confidence: 99%