Shear layer instabilities in low-density transverse jets

Getsinger, Daniel; Hendrickson, Cory; Karagozian, Ann

doi:10.1007/s00348-012-1329-x

Cited by 38 publications

(67 citation statements)

References 28 publications

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“…Similar V-shaped curves have been reported for other self-excited, but physically disparate, systems such as turbulent lean-premixed combustors (Bellows et al 2008), momentum-dominated low-density jets (Li & Juniper 2013a), laminar jet diffusion flames (Li & Juniper 2013b), low-density and equidensity cross-flowing jets (Davitian et al 2010;Getsinger, Hendrickson & Karagozian 2012), capillary jets (Olinger 1992) and cylinder wakes (Provansal, Mathis & Boyer 1987). The slope of the V is asymmetric about f f /f n = 1: lock-in occurs more readily for f f /f n > 1 than for f f /f n < 1.…”

Section: 4mentioning

confidence: 59%

“…The slope of the V is asymmetric about f f /f n = 1: lock-in occurs more readily for f f /f n > 1 than for f f /f n < 1. A similar asymmetry has been observed in laminar jet diffusion flames (Li & Juniper 2013b) and equidensity cross-flowing jets (Davitian et al 2010), but an opposite asymmetry has been observed in cylinder wakes (Blevins 1985), low-density cross-flowing jets (Getsinger et al 2012) and momentum-dominated low-density jets (Li & Juniper 2013a). The exact cause of the asymmetry is unknown.…”

Section: 4mentioning

confidence: 61%

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Forced synchronization of periodic and aperiodic thermoacoustic oscillations: lock-in, bifurcations and open-loop control

Kashinath

Juniper

2018

J. Fluid Mech.

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Synchronization is a universal concept in nonlinear science but has received little attention in thermoacoustics. In this numerical study, we take a dynamical systems approach to investigating the influence of harmonic acoustic forcing on three different types of self-excited thermoacoustic oscillations: periodic, quasi-periodic and chaotic. When the periodic system is forced, we find that: (i) at low forcing amplitudes, it responds at both the forcing frequency and the natural (self-excited) frequency, as well as at their linear combinations, indicating quasi-periodicity; (ii) above a critical forcing amplitude, the system locks in to the forcing; (iii) the bifurcations leading up to lock-in and the critical forcing amplitude required for lock-in depend on the proximity of the forcing frequency to the natural frequency; (iv) the response amplitude at lock-in may be larger or smaller than that of the unforced system and the system can exhibit hysteresis and the jump phenomenon owing to a cusp catastrophe; and (v) at forcing amplitudes above lock-in, the oscillations can become unstable and transition to chaos, or switch between different stable attractors depending on the forcing amplitude. When the quasi-periodic system is forced at a frequency equal to one of the two characteristic frequencies of the torus attractor, we find that lock-in occurs via a saddle-node bifurcation with frequency pulling. When the chaotic system is forced at a frequency close to the dominant frequency of its strange attractor, we find that it is possible to destroy chaos and establish stable periodic oscillations. These results show that the open-loop application of harmonic acoustic forcing can be an effective strategy for controlling periodic or aperiodic thermoacoustic oscillations. In some cases, we find that such forcing can reduce the response amplitude by up to 90 %, making it a viable way to weaken thermoacoustic oscillations.

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Section: 4mentioning

confidence: 59%

Section: 4mentioning

confidence: 61%

Forced synchronization of periodic and aperiodic thermoacoustic oscillations: lock-in, bifurcations and open-loop control

Kashinath

Juniper

2018

J. Fluid Mech.

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“…Like lock-in, quasiperiodicity has been observed in various forced self-excited flows, such as cylinder wakes (Van Atta & Gharib 1987;Karniadakis & Triantafyllou 1989), capillary jets (Olinger 1992), low-density jets (Juniper, Li & Nichols 2009), lowdensity and equidensity cross-flowing jets (Davitian et al 2010;Getsinger et al 2012) and jet diffusion flames (Li & Juniper 2013). Among these, cylinder wakes have received the most attention, forming the basis for much of the existing knowledge on the nonlinear dynamics of forced hydrodynamic oscillators.…”

Section: Introductionmentioning

confidence: 97%

“…This nonlinear adjustment process is known as synchronization, and the resulting synchronous state is known as lock-in (or phase locking; Balanov et al 2009). Lock-in has been observed in various forced self-excited flows, such as cylinder wakes (Koopmann 1967;Stansby 1976;Provansal, Mathis & Boyer 1987), capillary jets (Olinger 1992), low-density jets (Sreenivasan, Raghu & Kyle 1989;Hallberg & Strykowski 2008), low-density and equidensity crossflowing jets (Davitian et al 2010;Getsinger, Hendrickson & Karagozian 2012) and jet diffusion flames (Li & Juniper 2013).…”

Section: Introductionmentioning

confidence: 99%

Lock-in and quasiperiodicity in a forced hydrodynamically self-excited jet

Juniper

2013

J. Fluid Mech.

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The ability of hydrodynamically self-excited jets to lock into strong external forcing is well known. Their dynamics before lock-in and the specific bifurcations through which they lock in, however, are less well known. In this experimental study, we acoustically force a low-density jet around its natural global frequency. We examine its response leading up to lock-in and compare this to that of a forced van der Pol oscillator. We find that, when forced at increasing amplitudes, the jet undergoes a sequence of two nonlinear transitions: (i) from periodicity to T 2 quasiperiodicity via a torus-birth bifurcation; and then (ii) from T 2 quasiperiodicity to 1:1 lock-in via either a saddle-node bifurcation with frequency pulling, if the forcing and natural frequencies are close together, or a torus-death bifurcation without frequency pulling, but with a gradual suppression of the natural mode, if the two frequencies are far apart. We also find that the jet locks in most readily when forced close to its natural frequency, but that the details contain two asymmetries: the jet (i) locks in more readily and (ii) oscillates more strongly when it is forced below its natural frequency than when it is forced above it. Except for the second asymmetry, all of these transitions, bifurcations and dynamics are accurately reproduced by the forced van der Pol oscillator. This shows that this complex (infinite-dimensional) forced self-excited jet can be modelled reasonably well as a simple (three-dimensional) forced self-excited oscillator. This result adds to the growing evidence that open self-excited flows behave essentially like low-dimensional nonlinear dynamical systems. It also strengthens the universality of such flows, raising the possibility that more of them, including some industrially relevant flames, can be similarly modelled.

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“…They both affect the resulting mixing and how the resulting LIF signal is rendered, but they do not affect the spectroscopy of toluene itself. Injection of different fluids might also affect the fluid dynamics of the JISCF system [38,39]. We will first focus on the oxygen-free case, and later extend the analysis to the case with oxygen.…”

Section: Measurement Response Analysismentioning

confidence: 99%

Temperature and number density measurement in non-uniform supersonic flowfields undergoing mixing using toluene PLIF thermometry

et al. 2015

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visualization and quantification of many flow properties, including scalar concentration and temperature measurements, and it has been long used in both low-and highspeed flows. PLIF imaging based on a variety of tracers has been considered through the literature [1]. Historically, acetone and 3-pentanone [2, 3] have been widely used for scalar and temperature imaging, and more recently, naphthalene [4,5], krypton [6], 1-methylnaphthalene [7], and anisole [8] have been utilized in a variety of applications.Toluene has been identified as a versatile candidate for PLIF studies owing to its large fluorescence quantum yield and strong temperature sensitivity [9][10][11][12][13]. Toluene PLIF has found many applications for the study of mixing, especially in internal combustion engine studies [10,12,[14][15][16][17] where the strong oxygen quenching [18] has been used to obtain a direct measurement of air/fuel ratio [1,12,19]. Some of the challenges (particularly related to pressure effects) on the use of toluene for fuel/air ratio measurements have also been identified [12,15,20,21]. The properties of oxygen quenching on fluorescence have also been exploited for a direct measure of oxygen concentration in both single-tracer [22] and dual-tracer [23] configurations. Furthermore, because of the relatively large fluorescence quantum yield, toluene PLIF has also been successfully used for high-framing-rate imaging configurations where laser pulse energies are typically limited [14,20,24].Toluene PLIF has proven to be a particularly robust approach for temperature measurements. Both singleand dual-band-detection schemes have been proposed [10, 13] and applied [16,[25][26][27][28][29]. Its use as a thermometry technique stems from the strong temperature dependence of the integrated fluorescence quantum yield and the temperature-induced red shift of the spectral fluorescence Abstract Single-excitation, dual-band-collection toluene planar laser-induced fluorescence (PLIF) is used to measure temperature and number density (or partial pressure) fields in non-uniform supersonic complex flows in the presence of mixing and compressibility. The study provides a quantitative evaluation of the technique in transverse jets in supersonic crossflow (JISCF). It is found that toluene PLIF is highly effective in visualizing the structure of supersonic flows and that temperature can be accurately inferred with acceptable signal-to-noise ratios (of order 30) even when mixing occurs. The technique was applied to several JISCFs that differ by jet fluid properties with resulting different structures. In the presence of compressibility and mixing, it is found that the PLIF signal is non-unique, a feature that is used to identify the mixing region of the transverse jet. Measurement errors due to camera registration errors have also been quantified. Because of the complexity of the flowfield, it is found that minute misalignment (<0.1 pixels) between the two PLIF images can introduce measurable errors on the order of tens of Kelvins and significa...

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Shear layer instabilities in low-density transverse jets

Cited by 38 publications

References 28 publications

Forced synchronization of periodic and aperiodic thermoacoustic oscillations: lock-in, bifurcations and open-loop control

Forced synchronization of periodic and aperiodic thermoacoustic oscillations: lock-in, bifurcations and open-loop control

Lock-in and quasiperiodicity in a forced hydrodynamically self-excited jet

Temperature and number density measurement in non-uniform supersonic flowfields undergoing mixing using toluene PLIF thermometry

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