Computation of 3-D Compressible Flow From a Rectangular Nozzle With Delta Tabs

Reddy, Dhanireddy R.; Steffen, Christopher J.; Zaman, K. B. M. Q.

doi:10.1115/97-gt-257

Cited by 6 publications

(3 citation statements)

References 14 publications

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“…These results, for the first time, provide a proof that streamwise vortex pairs are indeed introduced by the tabs at supersonic conditions. There is a difference in the indicated amplitudes, but this is partly due to the velocity scale used in the non-dimensionalization (Reddy et al 1997). Ignoring this difference, the streamwise vorticity distribution in the tabbed jet under consideration is inferred to be essentially similar at subsonic and supersonic conditions.…”

Section: Streamwise Vorticity In the Tabbed Rectangular Jetmentioning

confidence: 99%

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Spreading characteristics of compressible jets from nozzles of various geometries

1999

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The spreading characteristics of jets from several asymmetric nozzles, and a set of rectangular orifices are compared, covering a jet Mach number range of 0.3-2.0. The effect of 'tabs' for a rectangular and a round nozzle is also included in the comparison. Compared to a round jet, the jets from the asymmetric nozzles spread only slightly more at subsonic conditions whereas at supersonic conditions, when 'screech' occurs, they spread much more. The dynamics of the azimuthal vortical structures of the jet, organized and intensified under the screeching condition, are thought to be responsible for the observed effect at supersonic conditions. Curiously, the jet from a 'lobed' nozzle spreads much less at supersonic condition compared to all other cases; this is due to the absence of screech with this nozzle. Screech stages inducing flapping, rather than varicose or helical, flow oscillation cause a more pronounced jet spreading. At subsonic conditions, only a slight increase in jet spreading with the asymmetric nozzles contrasts previous observations by others. The present results show that the spreading of most asymmetric jets is not much different from that of a round jet. This inference is further supported by data from the rectangular orifices. In fact, jets from the orifices with small aspect ratio (AR) exhibit virtually no increase in the spreading. A noticeable increase commences only when AR is larger than about 10. Thus, 'shear layer perimeter stretching', achieved with a larger AR for a given cross-sectional area of the orifice, by itself, proves to be a relatively inefficient mechanism for increasing jet spreading. In contrast, the presence of streamwise vortices or 'natural excitation' can cause a significant increase -effects that might explain the observations in the previous investigations. Thus far, the biggest increase in jet spreading is observed with the tabs. This is true in the subsonic regime, as well as in the supersonic regime, in spite of the fact that screech is eliminated by the tabs. The characteristic spreading of the tabbed jets is explained by the induced motion of the tab-generated streamwise vortex pairs. The tabs, however, incur thrust loss; the flow blockage and loss in thrust coefficient, vis-à-vis the spreading increase, are evaluated for various configurations.

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Section: Streamwise Vorticity In the Tabbed Rectangular Jetmentioning

confidence: 99%

“…inflow/outflow boundary conditions catering to the 'entrainment appetite' of the jet and grid generation for the tabbed nozzle geometry, were more difficult hurdles in the computation. For further details the reader is referred to Steffen et al (1997) and Reddy et al (1997).…”

Section: Streamwise Vorticity In the Tabbed Rectangular Jetmentioning

confidence: 99%

Spreading characteristics of compressible jets from nozzles of various geometries

1999

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“…Rectangular and square free jets received most of the attention (e.g. Berg et al, 2006;de With and Holdo, 2005;Imine et al, 2004;Wilson and Imber, 2003;Rembold et al, 2002;Abdel-Hameed and Bellan, 2002;Jiang and Luo, 2001;Reddy et al, 1998Reddy et al, , 1999Wilson and Demuren, 1998;Grinstein, 1998;Zaman et al, 1997;Grinstein and DeVore, HFF 19,7 896 1996;Miller et al, 1995;Grinstein and Kailasanath, 1995;Teshima, 1989;Quinn and Militzer, 1988). However, only a few numerical studies were devoted to triangular jets (Imine et al, 2004;Abdel-Hameed and Bellan, 2002;Miller et al, 1995).…”

Section: Introductionmentioning

confidence: 99%

Three‐dimensional numerical simulation of an equilateral triangular turbulent free jet

Shamami

Birouk

2009

Int Jnl of Num Meth for HFF

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Purpose -This paper aims to describe the numerical simulation of a three-dimensional turbulent free jet issuing from a sharp-edged equilateral triangular orifice into still air. Design/Methodology/approach -The numerical simulation was carried out by solving the governing three-dimensional Reynolds-averaged Navier-Stokes equations. Several two-equation eddyviscosity models (i.e. the standard k-", renormalization group (RNG) k-", realizable k-", shear-stress transport (SST) k-!), as well as the Reynolds stress models (i.e. the standard RSM and the SSG) were tested to simulate the flowfield. The numerical predictions were compared with experimental data in order to assess the capability and limitations of the various turbulent models examined in this work. Findings -The vena contracta effect was predicted by all the tested models. Among the eddyviscosity models only the realizable k-" model showed good agreement of the near-field jet decay. None of the eddy-viscosity models was capable of predicting the profiles of the jet turbulence intensities. The RSMs, especially the standard RSM, were able to produce much better predictions of the features of the jet in comparison with the eddy-viscosity models. The standard RSM predictions were found to agree reasonably well with the experimental data.Research limitations/implications -The conclusion, that among the tested RANS turbulence closure models, the RSM appeared the only one capable of reproducing reasonably well the experimental data concerns only the jet flow case examined here. Also, the average computational time for a single run was quite long, i.e. 340 h, but it is believed that parallel computing will reduce it considerably. Originality/value -The numerical results reported in this paper provide a comparison between several RANS turbulence closure models for simulating a turbulent free jet issuing from an equilateral triangular nozzle.

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