A study of the flow-field evolution and mixing 
in a planar turbulent jet using direct 
numerical simulation

Stanley, S. A.; Sarkar, Sutanu; Mellado, Juan Pedro

doi:10.1017/s0022112001006644

Cited by 206 publications

(161 citation statements)

References 39 publications

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“…Both thickness measurements are similar up to x/H ∼ 7, but δ Z becomes larger than δ 05 beyond this point. These results are consistent with those of Stanley et al (2002) for non-heated planar jets. They also observe a transition in growth rate around x/H ∼ 7 and a faster rate of mixing for the scalar profile beyond this point when compared to the rate of spread of the velocity profile.…”

Section: Statistical Characterization Of the Flowsupporting

confidence: 92%

“…We define the characteristic flow transient time as t L = L x /U j . Experience with this and other kinds of turbulent flows show that, in order to achieve well-converged first-order statistics one must sample the flow for approximately 10 t L (Stanley et al 2002;Jiménez 2003). In our case, such a simulation would have required approximately two years of computational time, with our present resources, and it is simply unattainable at this time.…”

Section: Statistical Characterization Of the Flowmentioning

confidence: 99%

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Direct simulation of non-premixed flame extinction in a methane–air jet with reduced chemistry

Pantano¹

2004

J. Fluid Mech.

111

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A three-dimensional direct numerical simulation (DNS) study of a spatially evolving planar turbulent reacting jet is reported. Combustion of methane with air is modelled using a four-step reduced mechanism in the non-premixed regime. A total of eight chemical species are integrated in time along with the fluid mechanical fields. The solution of the compressible Navier-Stokes equations is obtained numerically for moderately low Mach number. A large computational grid, with 100 million grid points, is required in order to resolve the flame. The cold flow Reynolds number is 3000. The focus of the study is to investigate the dynamics of extinction fronts in threedimensional turbulent flows. A novel data reduction and identification algorithm was developed to postprocess the large DNS database and extract the shape of the evolving flame surface including its edges and their propagation velocity. The joint probability density function (p.d.f.) of edge velocity and scalar dissipation was obtained and the results indicate that the three-dimensional flame edges propagate with a velocity that is largely controlled by the local rate of scalar dissipation, or equivalently in terms of the local Damköhler number at the flame edge, as predicted by theory. Naturally, the effects of unsteadiness in this flow produce a broad joint p.d.f. The statistics collected also suggest that the mean value of the hydrogen radical reaction rate are very small in the turbulent regions of the flow owing to the functional form of the hydrogen radical reaction rate itself. The consequence of these results in the context of turbulent combustion modelling is discussed. Additional statistical and morphological information of the flame is provided.

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Section: Statistical Characterization Of the Flowsupporting

confidence: 92%

Section: Statistical Characterization Of the Flowmentioning

confidence: 99%

Direct simulation of non-premixed flame extinction in a methane–air jet with reduced chemistry

Pantano¹

2004

J. Fluid Mech.

111

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“…9(b)) and other investigations on plane jet flows. 4,45 The one-dimensional streamwise component of the turbulent kinetic energy E k (x) is displayed in Figure 9 where E k (x) normalized by U 2 c (x). The data of Namar and Otugen 12 for the cases Re h = 1000-7000 are also included.…”

Section: Results and General Discussionmentioning

confidence: 99%

“…4,11,12 However, the role of the local Reynolds number, Re θ , based on the scale, θ m (x), is less clear in previous literature although this parameter is also known to evolve non-identically for jets measured at different Re h . 17 This is because, unlike a round jet where the Re θ is invariant, or for a planar wake flow where Re θ decreases, 22 that in a plane jet Re θ increases with x.…”

Section: -4mentioning

confidence: 99%

Similarity analysis of the momentum field of a subsonic, plane air jet with varying jet-exit and local Reynolds numbers

Deo

Nathan

2013

Physics of Fluids

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A similarity analysis is presented of the momentum field of a subsonic, plane air jet over the range of the jet-exit Reynolds number Reh (≡ Ubh/υ where Ub is the area-averaged exit velocity, h the slot height, and υ the kinematic viscosity) = 1500 − 16 500. In accordance with similarity principles, the mass flow rates, shear-layer momentum thicknesses, and integral length scales corresponding to the size of large-scale coherent eddy structures are found to increase linearly with the downstream distance from the nozzle exit (x) for all Reh. The autocorrelation measurements performed in the near jet confirmed reduced scale of the larger coherent eddies for increased Reh. The mean local Reynolds number, measured on the centerline and turbulent local Reynolds number measured in the shear-layer increases non-linearly following x1/2, and so does the Taylor microscale local Reynolds number that scales as x1/4. Consequently, the comparatively larger local Reynolds number for jets produced at higher Reh causes self-preservation of the fluctuating velocity closer to the nozzle exit plane. The near-field region characterized by over-shoots in turbulent kinetic energy spectra confirms the presence of large-scale eddy structures in the energy production zone. However, the faster rate of increase of the local Reynolds number with increasing x for jets measured at larger Reh is found to be associated with a wider inertial sub-range of the compensated energy spectra, where the −5/3 power law is noted. The downstream region corresponding to the production zone persists for longer x/h for jets measured at lower Reh. As Reh is increased, the larger width of the sub-range confirms the narrower dissipative range within the energy spectra. The variations of the dissipation rate (ɛ) of turbulent kinetic energy and the Kolmogorov (η) and Taylor (λ) microscales all obey similarity relationships, $\varepsilon h/U_{\rm b}^3 \sim Re_h^3$ɛh/Ub3∼Reh3, η/h ∼ Reh−3/4, and λ/h ∼ Reh−1/2. Finally, the underlying physical mechanisms related to discernible self-similar states and flow structures due to disparities in Reh and local Reynolds number is discussed.

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“…It was shown by other researchers (e.g. Stanly et al 2002) that, while the large scales in the flow field adjust slowly to variations in the local mean velocity gradients, the small scales adjust rapidly.…”

Section: Instantaneous Vorticity (ω Y )mentioning

confidence: 94%

Vorticity filaments beneath regular turbulent flow

Mukaro

2017

J. S. Afr. Inst. Civ. Eng.

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Two-dimensional vorticity flow fields created in the wake of a plunging breaker were investigated for regular turbulent flow at a Reynolds number of 30 000. Velocity flow fields obtained from an earlier study that had employed digital particle image velocimetry, were analysed to determine vorticity shedding patterns and the interactions between the vorticity filaments as flow progressed. Central difference approximations were applied to the velocity fields to determine vorticity at each point in the field. Most of the strong instantaneous vorticity observed in the flow field was in the form of filaments. A hierarchy of filaments of different lengths were observed, with the longest being as long as the height of the wave used. During the early phases of the flow, instantaneous vorticity tended to organise into thin filaments of counter-rotating pairs. Eventually, the co-rotating vorticity filaments coalesced and ultimately merged in the turbulent flow as flow progressed, while counter-rotating vorticity filaments were cancelled by viscous dissipation. The results suggested that filaments travel more slowly than the wave velocity and drifted towards the bed as they became elongated, and the number of filaments remaining in the flow were observed to decrease as flow progressed. Whereas phase-resolved instantaneous vorticity results showed pairs of counter-rotating vorticity filaments near the crest, the phase-averaged vorticity description of flow fields showed a dominant primary positive vorticity filament around the shear boundary layer.

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A study of the flow-field evolution and mixing in a planar turbulent jet using direct numerical simulation

Cited by 206 publications

References 39 publications

Direct simulation of non-premixed flame extinction in a methane–air jet with reduced chemistry

Direct simulation of non-premixed flame extinction in a methane–air jet with reduced chemistry

Similarity analysis of the momentum field of a subsonic, plane air jet with varying jet-exit and local Reynolds numbers

Vorticity filaments beneath regular turbulent flow

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