Effect of Wedge-Shaped Deflectors on Flow Fields of Dual-Stream Jets

Shupe, Rebecca S.; Zaman, K. B. M. Q.; Papamoschou, Dimitri

doi:10.2514/6.2007-3659

Cited by 11 publications

(12 citation statements)

References 9 publications

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“…The pear-shaped cross-sectional velocity contours near the end of the potential core show that there is a reduction in the radial gradient of mean velocity due to the thickening of the low speed fluid underneath the jet. Pear-shaped contours were also observed in a previous computational study, by Georgiadis and Papamoschou 13 , and also in experimental studies [2][3][4] . Note the reduction in potential core length, listed in Table 2.…”

Section: Resultssupporting

confidence: 58%

“…In the case of the external wedge-shaped deflector, asymmetry is created in the jet by causing the paths of the fluid elements near the top of the bypass duct to diverge toward the sides and beneath the jet. Regions of intense turbulent eddy formation are targeted by this method, and a thickened low-speed region results in reduced radial velocity gradients and peak turbulent kinetic energy levels in the lower hemi-cylinder of the jet 3 . Acoustic emissions over a range of azimuthal angles toward the ground are reduced 2 .…”

Section: Introductionmentioning

confidence: 99%

“…"Offset-stream" methods, tested extensively both at the University of California, Irvine and at NASA Glenn Research Center have demonstrated potential for application on commercial and military aircraft [1][2][3][4][5][6][7][8][9][10][11] . In the case of the external wedge-shaped deflector, asymmetry is created in the jet by causing the paths of the fluid elements near the top of the bypass duct to diverge toward the sides and beneath the jet.…”

Section: Introductionmentioning

confidence: 99%

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Flow Field of a Dual-Stream Jet with External Wedge-Shaped Deflector

Shupe

DeBonis

2008

46th AIAA Aerospace Sciences Meeting and Exhibit

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The research effort is a Reynolds-Averaged Navier-Stokes (RANS) investigation that looks at the flow-field and performance of a bypass ratio 8 nozzle with an external wedgeshaped noise suppressor, simulating the exhaust of a turbofan engine at takeoff conditions. Peak turbulence was reduced by the wedge on the side opposite the deflector, and it was increased in the initial region of the jet behind the deflector. Flow-field trends agreed with the expectations based on static jet experiments. The calculated thrust loss was 1.1% at takeoff conditions.

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Section: Resultssupporting

confidence: 58%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Flow Field of a Dual-Stream Jet with External Wedge-Shaped Deflector

Shupe

DeBonis

2008

46th AIAA Aerospace Sciences Meeting and Exhibit

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“…The present work extends previous concepts of wedge-shaped fan flow deflectors [1,[4][5][6] to wing-mounted turbofan engines incorporating a pylon. This type of engine installation is found in the majority of commercial jet aircraft.…”

mentioning

confidence: 90%

“…For typical fan-to-core velocity ratios in turbofan engines, the primary shear layer (between the core and fan flows) surrounded by the secondary core makes a negligible contribution to sound emission [2,3]. This ability of the secondary flow to silence the primary shear layer is the foundation of noisereduction concepts that extend the secondary core (via offset nozzles or deflectors) to cover a greater portion of the primary shear layer that emits downward noise [1,2,[4][5][6].…”

mentioning

confidence: 98%

Pylon-Based Jet Noise Suppressors

Papamoschou

2009

AIAA Journal

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This experimental investigation examined the potential of pylon-based deployable flaps to reduce jet noise of separate-flow turbofan engines with a bypass ratio of eight. The main function of the flap deflectors is to thicken the low-speed region surrounding the core jet in the downward and sideline directions. The study encompassed acoustic measurements, noise-source imaging, mean-velocity surveys, and aerodynamic estimates. Three types of deflectors were tested: solid flaps, porous flaps made of coarse perforation, and porous flaps made of fine perforation. It is shown that all the deflectors reduce noise sources near the end of the primary potential core. However, the solid flaps create excess noise in the vicinity of their location that can overwhelm this noise benefit, particularly at large polar angles. Porous flaps significantly reduce velocity gradients that cause excess noise. Noise generation from the perforations themselves can be shifted to very high frequency (rapidly attenuated by atmospheric absorption) by reducing the size of the perforation. Accordingly, the fine-perforation flaps provided superior acoustic results yielding effective perceived noise level benefits of 2.1 dB in the downward direction and 1.0 dB in the sideline direction. The static-thrust loss of these flaps is estimated at 0.7%.= fan nozzle exit height r = radial coordinate S = autospectrum of acoustic pressure Sr = Strouhal number U p = primary (core) exit velocity U s = secondary (fan) exit velocity u = axial mean velocity x = axial coordinate from exit of core nozzle y = transverse coordinate on symmetry plane z = transverse coordinate normal to symmetry plane = flap angle = polar angle from jet axis s = density of exit fan flow = azimuth angle measured from downward vertical = noise-source distribution

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Characteristics of a co-flowing jet with varying lip thickness and constant bypass ratio

Krishnan

2019

AEAT

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Purpose Subsonic commercial aircraft operate with turbo-fan engines that operate with moderate bypass ratio (BR) co-flowing jets (CFJ). This study aims to analyse CFJ with constant BR 6.3 and varying primary nozzle lip thickness (LT) to find a critical LT in CFJ below which mixing enhances and beyond which mixing inhibits. Design/methodology/approach CFJ were characterized with a constant BR of 6.3 and varying lip thicknesses. A single free jet with a diameter equal to that of a primary nozzle of the co-flowing jet was also studied for comparison. Findings The results show that within a critical limit, the mixing enhanced with an increase in LT. This was signified by a reduction in potential core length (PCL). Beyond this limit, mixing inhibited leading to the elongation of PCL. This limit was controlled by parameters such as LT and magnitude of BR. Practical implications The BR value of CFJ in the present study was 6.3. This lies under the moderate BR value at which subsonic commercial turbofan operates. Hence, it becomes impervious to study its mixing behavior. Originality/value This is the first effort to find the critical value of LT for a constant BR for compressible co-flow jets. The CFJ with moderate BR and varying LT has not been studied in the past. The present study focuses on finding a critical LT below which mixing enhances and above which mixing inhibits.

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Effect of Wedge-Shaped Deflectors on Flow Fields of Dual-Stream Jets

Cited by 11 publications

References 9 publications

Flow Field of a Dual-Stream Jet with External Wedge-Shaped Deflector

Flow Field of a Dual-Stream Jet with External Wedge-Shaped Deflector

Pylon-Based Jet Noise Suppressors

Characteristics of a co-flowing jet with varying lip thickness and constant bypass ratio

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