The organized nature of a turbulent trailing vortex

Bandyopadhyay, Promode R.; Ash, Robert L.

doi:10.2514/6.1990-1625

Cited by 8 publications

(12 citation statements)

References 6 publications

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“…It is clear from this figure that the current swirling air jets have the characteristic three-layer structure common to turbulent vortices. In addition to this evidence, LDV measurements (Cattafesta 1992) of swirling jets similar to those in cases 5-8 indicated that high levels of turbulence were present in the core, a characteristic also common to incompressible swirling flows generated by various means (Délery et al 1984;Bandyopadhyay, Stead & Ash 1991). The core turbulence quantities measured by Cattafesta (1992) are very similar to those observed in the wake of an axisymmetric body (Chevray 1968) with the exception of the persistence of significant turbulence levels at larger distances from the axis.…”

Section: Swirling-jet Flow-field Resultsmentioning

confidence: 79%

“…Although the former source is linked to the means of swirl generation used here, swirling flows generated by other means also contain high core turbulence levels (i.e. Délery et al 1984;Bandyopadhyay et al 1991). Therefore, the turbulence found in the present swirling jets should not be considered peculiar to the swirl-generation means used here.…”

Section: Discussion Of Resultsmentioning

confidence: 86%

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An experimental study of compressible turbulent mixing enhancement in swirling jets

1997

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Compressible jets with various amounts of swirl and compressibility are investigated experimentally. The mixing-layer growth rate is obtained from time-averaged images of the mixing layer using the planar laser scattering (PLS) technique, and the swirl is quantified with laser Doppler velocimetry and intrusive probes. The results conclusively demonstrate that the addition of swirl to the jet increases entrainment by up to 60% compared to a corresponding non-swirling case. Instantaneous PLS images reveal modified turbulent structure in the mixing layer of the swirling-jet cases. In particular, analysis of these images indicates that both the spatial extent and amplitude of the largest turbulent fluctuations are increased when swirl is added. Based upon these results, a parameter β that correlates the observed growth-rate enhancement is proposed. This parameter is derived assuming that the streamwise vorticity, generated in the mixing layer by the addition of small amounts of swirl, causes additional turbulent mixing that increases the growth rate. When the available growth-rate data for swirling jets are plotted against this parameter, they collapse to a single curve with increased enhancement for higher values of β. This result implies that the degree of enhancement actually increases with compressibility, although the dimensional growth rates for the present compressible swirling-jet cases are still less than those of their incompressible counterparts. † Present address: MCAT, Inc., Mountain View, CA 94043, USA.‡ Present address: High Technology Corporation, Hampton, VA 23666, USA.

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Section: Swirling-jet Flow-field Resultsmentioning

confidence: 79%

Section: Discussion Of Resultsmentioning

confidence: 86%

An experimental study of compressible turbulent mixing enhancement in swirling jets

1997

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“…With the notable exception of aircraft wake vortices, interacting vortices in nature are rarely of equal strength. Indeed, the interaction of vortices of very different strength is central to understanding vortex dissipation at high Reynolds number, as illustrated in the direct numerical simulation of vortex interaction with surrounding turbulence by Melander & Hussain (1993) and the experimental work on decay of airfoil trailing vortices subjected to surrounding turbulence by Bandyopadhyay, Stead & Ash (1991). This problem is fundamental to development of more physically grounded models for turbulence cascade processes and for subgrid-scale models used in large-eddy turbulence simulation.…”

Section: Introductionmentioning

confidence: 99%

Interaction of unequal anti-parallel vortex tubes

2001

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OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao.univ-toulouse.fr/ Eprints ID : 19705 A computational study is reported of the close interaction of nominally anti-parallel vortex tubes with unequal strengths,Γ 1 and −Γ 2 , whereΓ 2 /Γ 1 6 1. The computations are performed using a spectral method, with periodic boundary conditions and vortex Reynolds number Re ≡Γ 1 /ν = 1500, and the vortices are perturbed by a wavelength for which the pair is unstable because of their mutual interaction. The numerical method is tested for the case of equal-strength vortices, which exhibits the classic vortex reconnection phenomenon typified by bridging between the vortex cores and formation of thin vorticity threads as the bridged sections advect away under their self-induced velocity. Computations for vortices of unequal strengths are reported for cases with small, moderate and large strength differences, for whichΓ 2 /Γ 1 =0.82, 0.54 and 0.25 are chosen as representative values. The bridges between the vortex structures form loops that twist owing to the unequal vortex strengths. In the thread region, the vortex interaction is controlled by competition between the effects of stretching of the weak vortex as it wraps around the stronger vortex and the core distortion induced on each vortex owing to the straining imposed by the opposing vortex. For cases with large vortex strength difference, the strong vortex remains nearly straight as the weak vortex wraps around it, inducing an interlaced pattern of positive and negative vorticity spirals within the core of the strong vortex. Over long time, the bridge regions form loops that propagate away from the thread region for cases with small strength difference and wrap around the nearly columnar strong vortex for cases with large strength difference.

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“…et al (1996) Due to the absence of shear in the vortex core, turbulence production is considered to be negligible. Bandyopadhyay et al (1991) investigated the turbulence structure in a turbulent trailing vortex and concluded that the inner core region is not a complete laminar region; instead it is a re-laminarizing region where patches of turbulent fluid are intermittently brought in from the outer region.…”

Section: Wingtip Vorticesmentioning

confidence: 99%

“…high levels o f turbulence in the vortex core are not well understood. The high levels of turbulence in the vortex core can be due to vortex wandering (Khan and Johnston, 2000), entrainment o f surrounding turbulence (Bandyopadhyay et al, 1991), or the vortex core acting as a wave guide propagating disturbances that would have otherwise dissipated (Leibovich, 1984).…”

Section: Turbulence Distributionmentioning

confidence: 99%

Numerical simulations of turbulent flows

Johansen¹

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The organized nature of a turbulent trailing vortex

Cited by 8 publications

References 6 publications

An experimental study of compressible turbulent mixing enhancement in swirling jets

An experimental study of compressible turbulent mixing enhancement in swirling jets

Interaction of unequal anti-parallel vortex tubes

Numerical simulations of turbulent flows

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