Computational Analyses of Offset Stream Nozzles for Noise Reduction

Dippold, Vance F.; Foster, Lancert E.; Wiese, Michael

doi:10.2514/6.2007-3589

Cited by 8 publications

(4 citation statements)

References 13 publications

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“…As mentioned, reduction in the velocity gradient is expected to reduce the production rate for turbulent kinetic energy, k. Previous experiments and computations in dual-stream nozzles with fan flow deflectors have shown reduced values of k on the underside of the jet (Shupe et al 2007). Importantly, the experiments have shown a correlation between velocity gradients and the end of the potential core of the jet (Dippold et al 2007). Given that the jet has a finite axial extent, it is thus possible to reduce k throughout the underside of the jet.…”

Section: Fan Flow Deflectormentioning

confidence: 99%

Technologies for Jet Noise Reduction in Turbofan Engines

Gorji-Bandpy

Azimi

2012

Aviation

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Turbofan engines are commonly used for commercial transport due to their advantages of higher performance and lower noise. Jet noise is one of the principal noise sources of turbofan aeroplane engines and remains an acute environmental problem that requires advanced solutions. The ever-increasing demand for quieter engines requires the exploration of alternative techniques that could be used by themselves or in conjunction with existing methods. Significant progress continues to be made with noise reduction for turbofan engines. Analytical and semiempirical models have been developed to investigate the influence of some design tools when they are employed in a multidisciplinary optimisation framework. This paper discusses the major components of jet noise in turbofan engines and presents a review of jet noise reduction technologies.

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Section: Fan Flow Deflectormentioning

confidence: 99%

Technologies for Jet Noise Reduction in Turbofan Engines

Gorji-Bandpy

Azimi

2012

Aviation

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“…A separate paper details the parallel CFD analyses including performance predictions for these two concepts. 5 Computations for the vane deflectors included a detailed optimization. The performance predictions of all the OST nozzle concepts are compared here.…”

Section: Appendix: Performance Of All Offset Stream Technology Nozzlesmentioning

confidence: 99%

“…4 There are four other papers from the OST study that form a complete description of the program. A companion CFD study examining the vane deflector and s-duct nozzles was performed by Dippold et al 5 The experimental results from NATR, acoustics and Particle Image Velocimetry (PIV) based velocity measurements in the exhaust plume, were reported by Brown et al 6 and a comparison of experimental results between UCI and NASA Glenn was detailed by Zaman et al 7 The results of the DOE study were reported by Henderson et al 8 The experimental results at NATR indicate that the wedge deflectors do reduce the noise on the lower side of the nozzle at downstream angles. However, at other angles on the lower side and all angles on the sideline and upper side the noise was increased.…”

Section: Introductionmentioning

confidence: 99%

RANS Analyses of Turbofan Nozzles with Wedge Deflectors for Noise Reduction

DeBonis

2008

46th AIAA Aerospace Sciences Meeting and Exhibit

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Computational fluid dynamics (CFD) was used to evaluate a promising concept for reducing the noise at take-off of dual-stream, turbofan nozzles. The concept, offset stream technology, reduces the jet noise observed on the ground by diverting (offsetting) the majority of the fan flow below the core flow, thickening this layer between the high velocity core flow and the ground observers. In this study a wedge placed in the internal fan stream is used as the diverter. Wind, a Reynolds Averaged Navier-Stokes (RANS) code, was used to analyze the flowfield of the exhaust plume and to calculate nozzle performance. Results showed that the wedge effectively diverts the fan flow and the turbulent kinetic energy on the observer side of the nozzle is reduced. The reduction in turbulent kinetic energy should correspond to a reduction in noise. The blockage due to the wedge reduces the fan massflow proportional to its blockage and the overall thrust is consequently reduced. The CFD predictions are in very good agreement with experimental data. This noise reduction concept shows promise for reduced jet noise at a small reduction in thrust. It has been demonstrated that RANS CFD can be used to optimize this concept.

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“…Acoustic emissions over a range of azimuthal angles toward the ground are reduced 2 . This research effort continues a series of RANS investigations at the NASA John H. Glenn Research Center, that focus on the "offset-stream" methods for jet noise suppression [21][22][23][24][25] . In the current work, the emphasis is on the asymmetric jet resulting from an external wedge-shaped deflector placed in the bypass stream of a nozzle simulating takeoff conditions.…”

Section: Introductionmentioning

confidence: 99%

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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Computational Analyses of Offset Stream Nozzles for Noise Reduction

Cited by 8 publications

References 13 publications

Technologies for Jet Noise Reduction in Turbofan Engines

Technologies for Jet Noise Reduction in Turbofan Engines

RANS Analyses of Turbofan Nozzles with Wedge Deflectors for Noise Reduction

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

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