Investigation of Supersonic Turbulent Mixing Layer with Zero Pressure Gradient

Ikawa, Hideo; Kubota, T.

doi:10.2514/3.49766

Cited by 88 publications

(9 citation statements)

References 9 publications

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“…Although the spectra data of Spencer & Jones (1971) show 'spikes ' at low frequency, these data also illustrate that the spike magnitude attenuates with decreasing speed ratio. In a similar manner low frequency spectral peaks were found to disappear with increasing Reynolds number in the supersonic turbulent shear-layer experiments of Ikawa & Kubota (1975). The dependence of the shear-layer structure on the Reynolds number, speed ratio and even on the density ratio (Brown & Roshko 1974) therefore appears to require further evaluation, as already suggested by Chandrsuda et al (1977), Fiedler (1975) and Roshko (1976).…”

Section: Probability Density and Spectrasupporting

confidence: 68%

Turbulent mixing of passive and chemically reacting species in a low-speed shear layer

Batt

1977

J. Fluid Mech.

144

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A series of experiments has been conducted in a low-speed wind tunnel in which measurements were performed in a two-dimensional turbulent shear layer experiencing the mixing of both a passive and a chemically reacting species. The low-temperature air in the jet's primary flow was seeded with dilute concentrations of N2O4so that the dissociation reaction N2+ N2O4[harr ] 2NO2+ N2occurred in a near-equilibrium manner within the mixing layer owing to the turbulent mixing properties and the imposed temperature gradient. Mean and fluctuating values of velocity, temperature and NO2concentration were measured up to axial distances of 25 in. for jet velocities of 23 and 50ft/s (Rex[les ] 7 × 105) and for three primary temperatures (252, 273 and 305°K). Velocity and temperature measurements were performed with hot-wire probes, whereas a fibre optics light sensor probe was used to measure NO2concentrations. Local correlations between species and other fluid properties were obtained by positioning a hot-wire sensor within the light gap of the fibre optics probe and simultaneously recording output signals from both probes. A relatively complete set of turbulent statistics was measured for the non-reacting shear layer, including such results as temperature/species correlations, probability densities, filtered and unfiltered moving-frame velocities, skewness and flatness factors, spectra, velocity and temperature integral scales, intermittency factors for velocity, temperature and passive species, and conventional intensities. Some typical results from the investigation are as follows: the turbulent Schmidt and Lewis numbers were 0·5 and 1·0 respectively; the correlation between passive NO2concentration and temperature was approximately 0·95; dramatic changes consistent with equilibrium chemistry occurred in NO2concentration profiles with chemical reaction; velocity, temperature and concentration spectra were comparable over a 2½-decade range in wavenumber (k−2); spectra, probability densities, time-trace data and smoke-seeded shear-layer photographs indicate that, for axial locationsx=x0[ges ] 18·5 in. and for speedsu1[ges ] 23ft/s, undisturbed edge fluid rarely penetrates completely across the mixing region. Although not specifically addressed during the current study, measured results herein suggest that the turbulent motion for the present shear layer is characterized more by random and/or three-dimensionality effects than by large-scale two-dimensional coherent structures, as has been observed recently in other shear-layer investigations.

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Section: Probability Density and Spectrasupporting

confidence: 68%

Turbulent mixing of passive and chemically reacting species in a low-speed shear layer

Batt

1977

J. Fluid Mech.

144

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“…The same type of correlation used with the present growth rates can be applied to the growth rates measured by previous investigators. The experimental data are taken from Maydew & Reed (19631, Sirieix & Solignac (1966), Birch & Eggers (1973), and Ikawa & Kubota (1975). These investigators made probe measurements of vorticity thickness (8,) in shear layers with M , = 0 and both gases air.…”

Section: The Net Effect Of Compressibilitymentioning

confidence: 99%

The compressible turbulent shear layer: an experimental study

1988

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The growth rate and turbulent structure of the compressible, plane shear layer are investigated experimentally in a novel facility. I n this facility, it is possible to flow similar or dissimilar gases of different densities and to select different Mach numbers for each stream. Ten combinations of gases and Mach numbers are studied in which the free-stream Mach numbers range from 0.2 to 4. Schlieren photography of 20-ns exposure time reveals very low spreading rates and large-scale structures. The growth of the turbulent region is defined by means of Pitot-pressure profiles measured at several streamwise locations. A compressibility-effect parameter is defined that correlates and unifies the experimental results. It is the Mach number in a coordinate system convecting with the velocity of the dominant waves and structures of the shear layer, called here the convective Mach number. It happens to have nearly the same value for each stream. I n the current experiments, it ranges from 0 to 1.9. The correlations of the growth rate with convective Mach number fall approximately onto one curve when the growth rate is normalized by its incompressible value at the same velocity and density ratios. The normalized growth rate, which is unity for incompressible flow, decreases rapidly with increasing convective Mach number, reaching an asymptotic vaue of about 0.2 for supersonic convective Mach numbers.

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“…Recently there has been a growing interest in acquiring a better understanding of the underlying processes involved in supersonic mixing and combustion. Experimentally it has been found, for example by Ikawa & Kubota (1975), Bogdanoff (1983), Papamoschou & Roshko (1986) and Chinzei et al (1986), that the spreading or mixing rates of supersonic shear layers are considerably less than those a t subsonic speeds. The decrease is attributed to the effect of compressibility.…”

Section: Introductionmentioning

confidence: 97%

The instability and acoustic wave modes of supersonic mixing layers inside a rectangular channel

Tam

1989

J. Fluid Mech.

111

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At high supersonic convective Mach numbers the familiar Kelvin-Helmholtz instability of a thin unconfined two-dimensional shear layer becomes neutrally stable. In this paper, it is shown that when the same shear layer is put inside a rectangular channel the coupling between the motion of the shear layer and the acoustic modes of the channel produces new two-dimensional instability waves. The instability mechanism of these waves is examined. Extensive numerical computation of the properties of these new instability waves has been carried out. Based on these results two classes of these waves are identified. Some of the important characteristic features of these waves are reported in this paper. In addition to the unstable waves, a thorough analysis of the normal modes of a supersonic shear layer inside a rectangular channel reveals that there are basically two other families of neutral acoustic waves. Examples of some of the prominent characteristics of these neutral acoustic waves are also provided in this paper. The new instability waves are the dominant instabilities of a confined mixing layer at high supersonic convective Mach number. As such they are very relevant to the supersonic mixing and combustion processes inside a ramjet engine combustion chamber.

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Investigation of Supersonic Turbulent Mixing Layer with Zero Pressure Gradient

Cited by 88 publications

References 9 publications

Turbulent mixing of passive and chemically reacting species in a low-speed shear layer

Turbulent mixing of passive and chemically reacting species in a low-speed shear layer

The compressible turbulent shear layer: an experimental study

The instability and acoustic wave modes of supersonic mixing layers inside a rectangular channel

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