Computational fluid dynamics (CFD) was used to evaluate the flow field and thrust performance of 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) a portion of the fan flow below the core flow, thickening and lengthening 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 flow field of the exhaust plume and to calculate nozzle performance. Results showed that the wedge diverts all of the fan flow to the lower side of the nozzle, and the turbulent kinetic energy on the observer side of the nozzle is reduced. This reduction in turbulent kinetic energy should correspond to a reduction in noise. However, because all of the fan flow is diverted, the upper portion of the core flow is exposed to the freestream, and the turbulent kinetic energy on the upper side of the nozzle is increased, creating an unintended noise source. The blockage due to the wedge reduces the fan mass flow proportional to its blockage, and the overall thrust is consequently reduced. The CFD predictions are in very good agreement with experimental flow field data, demonstrating that RANS CFD can accurately predict the velocity and turbulent kinetic energy fields. While this initial design of a large scale wedge nozzle did not meet noise reduction or thrust goals, this study identified areas for improvement and demonstrated that RANS CFD can be used to improve the concept.
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April 2009
Research Papers
RANS Analyses of Turbofan Nozzles With Internal Wedge Deflectors for Noise Reduction
James R. DeBonis
James R. DeBonis
Inlet and Nozzle Branch,
e-mail: james.r.debonis@nasa.gov
NASA Glenn Research Center
, Cleveland, OH 44135
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James R. DeBonis
Inlet and Nozzle Branch,
NASA Glenn Research Center
, Cleveland, OH 44135e-mail: james.r.debonis@nasa.gov
J. Fluids Eng. Apr 2009, 131(4): 041104 (17 pages)
Published Online: March 9, 2009
Article history
Received:
March 21, 2008
Revised:
January 22, 2009
Published:
March 9, 2009
Citation
DeBonis, J. R. (March 9, 2009). "RANS Analyses of Turbofan Nozzles With Internal Wedge Deflectors for Noise Reduction." ASME. J. Fluids Eng. April 2009; 131(4): 041104. https://doi.org/10.1115/1.3089536
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