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Aerodynamic and Acoustic Design of Silent Leading Edge Devices

Pott-Pollenske, Michael and Wild, Jochen and Bertsch, Lothar (2014) Aerodynamic and Acoustic Design of Silent Leading Edge Devices. 20th AIAA/CEAS Aeroacoustics Conference, 16. - 20. Juni 2014, Atlanta, USA.

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The high lift system noise of current transport aircraft is dominated by slat noise under certain operating conditions. Suitable means to reduce the noise impact in the vicinity of airports are (i) to increase the distance between the source and the observer and (ii) to reduce source noise levels. Both objectives can only be achieved by means of a multi-disciplinary aerodynamic and acoustic development since the slat is at the same time a very important element to achieve the necessary high lift performance and the dominant noise source of a high lift system1. First attempts to reduce slat noise by means of a slat setting optimization were conducted at DLR in the mainframe of the project Leiser Flugverkehr2. This purely acoustically driven study revealed that a slat gap reduction results in a local flow speed decrease at the slat trailing edge and thus to remarkable noise reductions of up to 10 dB, the latter of course depending on the magnitude of the slat gap reduction. The drawback of this approach was that at the same time the aerodynamic performance of the high lift system was degraded by a non-acceptable level. However, this study was the starting point of the DLR project LEISA (Low noise exposing integrated design for start and approach) that combined activities in the research areas of high lift system design and aero-acoustic design, which were carried out rather independently up to this point in time. In the project LEISA different types of high lift configurations were addressed and investigated in a 2-dimensional approach. The first one is a long chord slat that provided a source noise reduction of about 6 dB while maintaining the aerodynamic performance of the reference slat system. The second, and more radical concept was to omit the slat and apply a droop nose system in order to reduce the aerodynamic losses as much as possible. The finally achieved source noise reduction with the droop nose system was about 8 dB while from the aerodynamic point of view about 50% of the losses were recovered. Based on these promising results the transposition of these high lift systems to a real 3-dimensional wing was carried out in the follow-up project SLED (Silent Leading Edge Devices). The final outcome of the project SLED can be summarized as follows. From the aerodynamic point of view the performance of the 3-dimensional long chord slat compares very well to the reference slat system. The final droop nose design was capable to recover about 40% of the lift loss due the omitted slat. The final acoustic results in terms of source noise levels are an overall 4 dB noise reduction for the long chord slat and about 6 dB noise reduction in case of the droop nose. The obtained aerodynamic and acoustic characteristics were finally transposed to flight in order to assess the effect on community noise which can be expressed in terms of noise iso-contour areas. Regarding the 60 dB(A) and the 65 dB(A) noise iso contour areas the achieved benefit is a reduction of up to 40% of the respective area’s size.

Item URL in elib:https://elib.dlr.de/92547/
Document Type:Conference or Workshop Item (Speech)
Title:Aerodynamic and Acoustic Design of Silent Leading Edge Devices
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Date:June 2014
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:No
Keywords:Airframe Noise, High Lift Design, Community Noise
Event Title:20th AIAA/CEAS Aeroacoustics Conference
Event Location:Atlanta, USA
Event Type:international Conference
Event Dates:16. - 20. Juni 2014
Organizer:American Institute for Aeronautics and Astronautics
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:fixed-wing aircraft
DLR - Research area:Aeronautics
DLR - Program:L AR - Aircraft Research
DLR - Research theme (Project):L - Flight Physics (old)
Location: Braunschweig , Göttingen
Institutes and Institutions:Institute of Aerodynamics and Flow Technology > Technical Acoustics
Institute of Aerodynamics and Flow Technology > Transport Aircraft
Institute of Aerodynamics and Flow Technology > Helicopters
Deposited By: Pott-Pollenske, Stephan-Michael
Deposited On:25 Nov 2014 15:21
Last Modified:25 Nov 2014 15:21

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