Instantaneous mole-fraction PLIF imaging of mixing layers behind hypermixing injectors

Fox, J.S.; Gaston, M.; Danehy, Paul M.; Mudford, N. R.; Houwing, A. F. P.; Gai, S. L.

doi:10.2514/6.1999-774

Cited by 6 publications

(10 citation statements)

References 15 publications

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“…Studies to this point have been concerned primarily with the mixing enhancement induced by the hypermixer [3][4][5][6][7][8][9][10][11][12][13]. Doster et al [3,4] have performed complimentary experimental and computational studies on three primary hypermixing geometries with upstream scalar injection including a base supersonic wake, an alternating ramp mixer, and an alternating wedge mixer.…”

Section: Introductionmentioning

confidence: 99%

“…The current joint study seeks to investigate the mixing characteristics of the flow downstream of the strut-based hypermixer through experimental and computational means. A hypermixer featuring a central castellation with expansive wedges was selected as it was shown to have the most significant impact on the flow-field [5][6][7], and poses complex interactions to challenge the LES models. Laser-based diagnostic techniques were employed to study the mixing characteristics of the flow-field.…”

Section: Introductionmentioning

confidence: 99%

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Experimental and Computational Studies of Mixing in Supersonic Flow

Burns

Koo

Clemens

et al. 2011

41st AIAA Fluid Dynamics Conference and Exhibit

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A preliminary combined experimental and computational investigation is conducted on the mixing characteristics of a strut-based hypermixer in a Mach 3 freestream. The hypermixing flow-field is generated by an injection pylon with expansive wedges to enhance the streamwise vorticity. Two different scalar visualization techniques are used to examine the underlying mixing processes. Planar laser scattering of condensed carbon dioxide gas is used to visualize the freestream flow, whereas two-photon planar laser-induced fluorescence (PLIF) of krypton gas is used to mark the injected jet fluid. The experimental results are compared directly to a large-eddy simulation (LES) of the same flow-field. The results obtained are complimentary because the experimental data can aid in the validation of LES models, and the simulations provide information about the thermodynamic property variations that affect the interpretation of the krypton PLIF signal.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental and Computational Studies of Mixing in Supersonic Flow

Burns

Koo

Clemens

et al. 2011

41st AIAA Fluid Dynamics Conference and Exhibit

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“…This gate was long enough to capture over 90% of the uorescence while short enough to reject the majority of the natural ow luminosity. A more detailed description of the optical setup is provided by Fox et al 33 …”

Section: Plif Excitation and Detectionmentioning

confidence: 99%

Fluorescence Visualization of Hypersonic Flow Establishment over a Blunt Fin

et al. 2001

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Fluorescence imaging is used to investigate the separated ow upstream of a blunt n in a hypersonic freestream with a transitional boundary layer. Images are presented to show the ow development before, during, and after the test time of the free-piston shock tunnel used to generate the ow. These images indicate that the test time in this facility is long enough to achieve a steady ow over the blunt n. Thermocouple measurements are included to compare the surface heat ux upstream of the n with that for ow along a at plate with the same freestream conditions. The heat ux results are consistent with separation in a transitional boundary layer and show that the separated ow is oscillatory. Nomenclaturespeci c enthalpy of freestream, J ¢ kg ¡1 h w = speci c enthalpy at wall, J ¢ kg ¡1 h 1 = verticle distance from plate to triple point, m h 2 = vertical distance from plate to shear layer below triple point, m L = length of at plate, m l sep = separation length, m M = Mach number M 1 = Mach number in freestream Pr = Prandtl number p pitot;1 = pitot pressure, Pa p 0 = nozzle reservoir pressure, Pa P q s .t / = surface heat ux, J ¢ m ¡2 ¢ s ¡1 R = gas constant, J/(kg ¢ K) Re = Reynolds number St = Stanton number based on freestream conditions T = temperature, K T w = temperature at wall, K T 1 = temperature in freestream, K T ¤ = Eckert reference temperature, K t = time, s U = velocity, m ¢ s ¡1 U 1 = ow speed ahead of the bow shock, m ¢ s ¡1 u e = velocity of freestream, m ¢ s ¡1 X= position at which 1t N T is evaluated, m x = distance from nozzle throat along nozzle axis, m ® 1 = angle of separation shock with horizontal, deg ® 2 = angle of shear layer with horizontal, deg ®¸= angle of lambda shock with horizontal, deg°= ratio of speci c heats°1 = ratio of speci c heats in freestream 1 = asymptotic value of shock standoff distance, m 1t E = time to establish overall ow, s 1t E ;max = maximum time to establish overall ow, s 1t E ;min = minimum time to establish overall ow, s 1t nozzle = time to establish nozzle ow, s 1t N T = time for sound waves to travel through nozzle, s 1 0 = shock standoff distance when established, m ½ e = density of freestream, kg ¢ m 3 ½ s = density behind bow shock, kg ¢ m 3 ½ 1 = density ahead of bow shock, kg ¢ m 3 ¿ bl = characteristic response time (boundary layer), s ¿ bs = characteristic response time (bow shock), s ¿ sep = characteristic response time (separated ow), s

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“…Later studies to the same effect utilized PLIF of nitric oxide (NO) in a shock tunnel. [7][8][9] In particular, a baseline case of a planar hypermixing flowfield was compared to various castellated and compressive hypermixers, drawing much the same conclusion about the mixing enhancement.…”

Section: Introductionmentioning

confidence: 98%

“…[5][6][7][8][9][10][11][12][13][14][15][16][17][18] In this strategy, geometrically-induced pressure gradients are used to generate or increase the streamwise vorticity present in the flow. For strut-based schemes, this is often achieved through the use of alternating compressive and/or expansive surfaces on the trailing edge of the pylon, while for wall-based schemes it is achieved through oblique injection from a swept compressive ramp.…”

Section: Introductionmentioning

confidence: 99%

Scalar and Velocity Measurements in a Mach 3 Hypermixing Flowfield

Burns

Clemens

2012

50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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Mach 3 hypermixer flowfields are studied by using scalar and velocity imaging techniques. Two strut-based hypermixer configurations are used that feature parallel gas injection through a castellated base with (i) expansive wedges flanking the base, and (ii) a combination of compressive and expansive wedges near the base. Two-component particle image velocimetry (PIV) is used to obtain the velocity fields, planar laser scattering (PLS) of condensed carbon dioxide gas is used to visualize the freestream flow structures, and planar laser-induced fluorescence (PLIF) of acetone vapor is used to tag the injected jet fluid. In the cases with no base injection, the two wakes show notable differences, with the compressive mixer entraining large quantities of freestream fluid within the wake in contrast to the expansive mixer. With the addition of base injection, the expansive mixer is found to induce notable transverse spread of the injected jet fluid though spanwise spread is limited. The compressive mixer enhances the spread of the injected fluid in both the spanwise and transverse directions. The velocity measurements show that rapid transverse spread of the jet in the compressive hypermixer is the result of a large transverse velocity component induced by the strong streamwise vortices. These vortices are so strong as to create a bifurcation of the jet fluid along the midplane of the hypermixer.

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Instantaneous mole-fraction PLIF imaging of mixing layers behind hypermixing injectors

Cited by 6 publications

References 15 publications

Experimental and Computational Studies of Mixing in Supersonic Flow

Experimental and Computational Studies of Mixing in Supersonic Flow

Fluorescence Visualization of Hypersonic Flow Establishment over a Blunt Fin

Scalar and Velocity Measurements in a Mach 3 Hypermixing Flowfield

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