Experimental and Numerical Investigation of a Supersonic C-D Chevron Nozzle

Burak, Markus Olander; Eriksson, Lars‐Erik; Munday, David; Gutmark, Ephraim; Prisell, Erik

doi:10.2514/6.2009-4004

Cited by 9 publications

(5 citation statements)

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“…Bridges et al 12 identified issues in generating streamwise vorticity in overexpanded conditions due to the inherent contraction of the flow field at the nozzle exit. Similar findings were presented by Munday et al 13 and Kuo et al 14 Bridges et al 12 also found that the peak vorticity magnitudes roughly two diameters downstream of the nozzle were independent of initial values, though the spatial extent of the structures varied depending on the initial configuration, similar to what was presented by Opalski et al 9 Burak et al 15 noted the presence of a secondary counter rotating streamwise vortex pair in addition to the primary pair reported in most studies. Investigation of streamwise vorticity introduction into supersonic jets has typically been performed using sonic nozzles, limiting results to sonic and under expanded conditions.…”

Section: Introductionsupporting

confidence: 82%

“…These secondary structures rotate in an opposite fashion compared to the primary pair, as is particularly evident for the low penetration vortex generator configuration ( Figure 6(d)). Similar vorticity features were reported in the computational study of Burak et al 15 In an effort to quantify the effect of penetration on the vorticity field, the maximum vorticity was initially tabulated at each available axial location as presented in Figures 7 and 8. An exponential function was also fit to each of the vortex generator configurations to illustrate the decay rate following the results of Alkislar et al 33 As expected from the above vorticity contour plots, the overexpanded results show initial maximum vorticity that is much higher for the medium and high penetration vortex generators than the baseline and low penetration vortex generators.…”

Section: Resultsmentioning

confidence: 89%

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An experimental investigation of the flow dynamics of streamwise vortices of various strengths interacting with a supersonic jet

2014

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The results of an experimental study involving the introduction of streamwise vorticity into a supersonic jet are presented. Both streamwise and cross stream PIV measurements of a baseline jet and three vortex generator configurations of varied penetration were acquired in the overexpanded, ideally expanded, and underexpanded regimes. Streamwise vortex pairs were shown to persist no further than two diameters downstream independent of initial magnitude. Integration of the modulus of streamwise vorticity was shown to better correlate with secondary flow field modifications than maximum values. Reductions in shock cell spacing and downstream turbulence, and increases in initial spread rate and upstream integrated turbulence were correlated with increases in streamwise vorticity for all operating conditions. Streamwise vorticity was shown to achieve opposite effects on shock strength in the over/under expanded regimes due to introduction of secondary shock structures in the underexpanded case. Additionally, limited effect on potential core length was quantified.

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Section: Introductionsupporting

confidence: 82%

Section: Resultsmentioning

confidence: 89%

An experimental investigation of the flow dynamics of streamwise vortices of various strengths interacting with a supersonic jet

2014

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“…Cuppoletti et al 6 showed significant reduction of BBSN and screech through use of fluidic injection at the nozzle exit to interrupt the jet shock structure. Experiments have been performed at the University of Cincinnati and LES computations have been performed at Chalmers University of Technology, where the noise from a convergentdivergent nozzle was studied 7,8 . These studies were conducted on a conical converging-diverging (C-D) nozzle with a sharp throat.…”

Section: Introductionmentioning

confidence: 99%

Nozzle throat optimization for supersonic jet noise reduction

Gustafsson

Cuppoletti

Gutmark

et al. 2012

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

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Noise from engines that operate at supersonic conditions, especially high performance military aircraft, often utilize a converging-diverging nozzle with variable area control. This design usually includes a sharp nozzle throat which creates internal shock formation. Turbulent structure interaction with these shocks results in additional noise components other than turbulent mixing noise to be introduced to the jet noise spectrum. The present study investigates how weakening the internal shocks affects the flow and acoustics of a Mach 1.6 jet. RANS simulations were used to minimize internal shock formation and optimize the flow contours of the converging portion and throat of a C-D nozzle. A response surface methodology was used to evaluate 3000 possible designs using the RANS results as model inputs. An experimental investigation was conducted with a splined nozzle design that is virtually free of internal shocks. The flow field was measured using PIV for comparison with RANS and LES. Mean velocity and turbulence was captured well by the computations for the sharp throat and splined nozzles. Although the throat shocks were nearly eliminated, the overall shock strength was relatively unchanged. Far-field acoustic results showed little difference at thrust matched conditions since the overall shock strength was unchanged. The nozzle performance is greatly improved through throat optimization, providing equivalent thrust with 4% less pressure with no acoustic penalty. NomenclatureA = area PIV = particle image velocimetry AR = ratio of exit area to throat area r = radial coordinate BBSN = broad-band shock associated noise R C = radius of throat corner C d = discharge coefficient R T = throat radius C fg = gross thrust coefficient RANS = Reynolds Averaged Navier-Stokes D j = jet exit diameter T = temperature  = rate of dissipation of k TKE; k = turbulent kinetic energy L C = length of convergent section U j = isentropic jet exit velocity LES = large eddy simulation x = axial coordinate NPR = nozzle pressure ratio, P tot,in /P amb  conv = angle of convergent section OASPL = overall sound pressure level  = turbulent frequency P = pressure P amb = ambient pressure  1

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“…The direction of rotation of these secondary structures was opposite compared to the primary pair. Burak et al [66] presented similar vorticity features in a computational study of chevrons.…”

Section: Flow Fieldmentioning

confidence: 56%