Scaling parameters for underexpanded supersonic jets

Yuceil, K. B.; Otugen, M. V.

doi:10.1063/1.1513796

Cited by 92 publications

(55 citation statements)

References 11 publications

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“…16, we have k ∼ π /D for NPR = 4.5 and k ∼ 2π /D otherwise. The antisymmetry shown earlier for mode pair (1,2) gives an azimuthal wavenumber |m| = 1 and characterizes the helical mode. Gutmark et al 49 reported that the dominant mode in a similar configuration satisfied |m| = 1, supporting the present finding.…”

Section: G Proper Orthogonal Decompositionmentioning

confidence: 99%

“…[1][2][3][4][5][6][7] Such high speed jets can also be observed in geophysical applications, for example, volcano eruptions release large amounts of gas in the atmosphere featuring weak shocks, compression waves and Machdisks. 8 Other examples are jet formation during accidental release of pressurized hydrogen through a small hole or a crack.…”

Section: Introductionmentioning

confidence: 99%

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Large-eddy simulation of highly underexpanded transient gas jets

Vuorinen¹,

Yu²,

Tirunagari³

et al. 2013

Physics of Fluids

157

142

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Large-eddy simulations (LES) based on scale-selective implicit filtering are carried out in order to study the effect of nozzle pressure ratios on the characteristics of highly underexpanded jets. Pressure ratios ranging from 4.5 to 8.5 with Reynolds numbers of the order 75 000-140 000 are considered. The studied configuration agrees well with the classical picture of the structure of highly underexpanded jets. Similarities and differences between simulation and experiments are discussed by comparing the concentration field structures from LES and planar laser induced fluorescence data. The transient stages, leading eventually to the highly underexpanded state, are visualized and investigated in terms of a phase diagram revealing the shock speeds and duration of the transient stages. For the studied nozzle pressure ratio range, the Mach disk dimensions are found to be in good agreement with literature data and experimental observations. It is observed how the nozzle pressure ratio influences the Mach disk width, and thereby the slip line separation, which leads to co-annular jets with inner and outer shear layers at higher pressure ratios. The improved mixing with increasing pressure ratio is demonstrated by the probability density functions of the concentration. The coherent structures downstream of the Mach disk are identified using proper orthogonal decomposition (POD). The structures indicate a helical mode originating from the shear layers of the jet. Despite the relatively low energy content of the dominant POD modes, the frequencies of the POD time coefficients explain the dominant frequencies in the pressure fluctuation spectra. C

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Section: G Proper Orthogonal Decompositionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Large-eddy simulation of highly underexpanded transient gas jets

Vuorinen¹,

Yu²,

Tirunagari³

et al. 2013

Physics of Fluids

157

142

View full text Add to dashboard Cite

show abstract

“…The majority of leak scenarios will occur from a pressurized source creating an under-expanded jet. Notional nozzle models allow the replacement of the compressible aspect of the jet with atmospheric equivalent boundary conditions (Birch et al 1984(Birch et al , 1987Ewan and Moodie 1986;Harstad and Bellan 2006;Yuceil and Otugen 2002), after which the jet is regarded as atmospheric and modeled thusly. A recent study concluded that the downstream aspect of an underexpanded jet conforms to the current self-similarity assessment (Ruggles and Ekoto 2012).…”

Section: Introductionmentioning

confidence: 99%

Statistically advanced, self-similar, radial probability density functions of atmospheric and under-expanded hydrogen jets

Ruggles

2015

Exp Fluids

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used to separate the turbulent and pure air data, and thusly estimate intermittency. Beta-distributions (four parameters) are used to accurately represent the turbulent distribution moments. This combination of measured intermittency and four-parameter beta-distributions constitutes a new, simple approach to model scalar mixing. Comparisons between global moments from the data and moments calculated using the proposed model show excellent agreement. This was attributed to the high quality of the measurements which reduced the width of the correctly identified, noiseaffected pure air distribution, with respect to the turbulent mixing distribution. The ignitability of the atmospheric jet is determined using the flammability factor calculated from both kernel density estimated (KDE) PDFs and PDFs generated using the newly proposed model. Agreement between contours from both approaches is excellent. Ignitability of the under-expanded jet is also calculated using KDE PDFs. Contours are compared with those calculated by applying the atmospheric model to the under-expanded jet. Once again, agreement is excellent. This work demonstrates that self-similar scalar mixing statistics and ignitability of atmospheric jets can be accurately described by the proposed model. This description can be applied with confidence to under-expanded jets, which are more realistic of leak and fuel injection scenarios.Abstract This paper presents improved statistical insight regarding the self-similar scalar mixing process of atmospheric hydrogen jets and the downstream region of underexpanded hydrogen jets. Quantitative planar laser Rayleigh scattering imaging is used to probe both jets. The self-similarity of statistical moments up to the sixth order (beyond the literature established second order) is documented in both cases. This is achieved using a novel self-similar normalization method that facilitated a degree of statistical convergence that is typically limited to continuous, pointbased measurements. This demonstrates that image-based measurements of a limited number of samples can be used for self-similar scalar mixing studies. Both jets exhibit the same radial trends of these moments demonstrating that advanced atmospheric self-similarity can be applied in the analysis of under-expanded jets. Self-similar histograms away from the centerline are shown to be the combination of two distributions. The first is attributed to turbulent mixing. The second, a symmetric Poisson-type distribution centered on zero mass fraction, progressively becomes the dominant and eventually sole distribution at the edge of the jet. This distribution is attributed to shot noise-affected pure air measurements, rather than a diffusive superlayer at the jet boundary. This conclusion is reached after a rigorous measurement uncertainty analysis and inspection of pure air data collected with each hydrogen data set. A threshold based upon the measurement noise analysis is

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“…(Note in Figure 5 that the CFD solution has a recirculation region attached to the outer shroud that slows the flow at this location.) In the downstream portion of the jet, a velocity profile 12 approximating a Gaussian distribution, should be reached as shown by the CFD calculation, but an approximate "top hat" profile is shown by the instantaneous measured data instead (Fig. 9(b)).…”

Section: B Streamwise Velocity Profiles Near Thementioning

confidence: 99%