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Kopiev V.F.,RAS Institute of Radio Engineering and Electronics | Zaytsev M.Y.,RAS Institute of Radio Engineering and Electronics | Belyaev I.V.,RAS Institute of Radio Engineering and Electronics | Gorbushin A.R.,Central Aerohydrodynamics Institute TsAGI | And 2 more authors.
20th AIAA/CEAS Aeroacoustics Conference | Year: 2014

Experimental investigation of aeroacoustic and aerodynamic characteristics of a large-scale semi-span wing model in approach configuration has been performed in aeroacoustic wind tunnel DNW-NWB. Effect of Reynolds number on airframe noise, as well as noise reduction concepts for slat noise have been studied. A comparison of the aerodynamic results obtained in DNW-NWB for chevron slat and reference slat configuration is also provided.

Herrmann D.,German Aerospace Center | Herrmann D.,Institute of Aerodynamic and Flow Technology | Gulhan A.,German Aerospace Center | Gulhan A.,Institute of Aerodynamic and Flow Technology
Journal of Propulsion and Power | Year: 2010

The dependency of the performance of a two-dimensional intake for air-breathing missiles on intake orientation has been investigated experimentally. The main objective of the study is to identify the ideal intake position on the missile body. Experiments have therefore been carried out at combinations of different angles of attack and different roll angles of the intake and the missile body. All tests were performed at the intake design Mach number of 2.5 and at angles of attack ranging from 0 to 30° in the Trisonic Wind Tunnel Cologne. The results show that the ideal intake position depends on boundary-layer flow, flow separation, and vortices, which vary with different angles of attack. Furthermore, some intake orientations show a mass flow rise on the windward side, where the intake could be located. © 2010 by Dirk Herrmann.

Stahl B.,Institute of Aerodynamic and Flow Technology | Siebe F.,Institute of Aerodynamic and Flow Technology | Gulhan A.,Institute of Aerodynamic and Flow Technology
Journal of Spacecraft and Rockets | Year: 2010

The present paper reports on the interaction of a hot side jet in a supersonic freestream and compares the effects with results from cold-gas jet investigations. With high-speed schlieren videos, a significant enlargement of the separation area has been ascertained upstream from the hot-gas jet and quantitatively confirmed with wall pressure measurements. The schlieren videos also show a strong oscillation of the separation and bow shock. By using an algorithm that analyzes the similarity of neighboring images, the oscillation frequency of the separation and bow shock has been measured to be 11.3 kHz. As a consequence of the dominant shocks in the area in front of the jet, the hot jet plume is screened off strongly from the freestream, thus resulting in an upstream inclination. Finally, highspeed videos have revealed large-scale structures in the hot-gas jet and their convection velocities have been analyzed. According to the shocks, the large-scale structures oscillate at 11.3 kHz. Jet oscillation is thus excited by the interaction of the hot-gas jet with the freestream and not by resonances from the combustion chamber. © 2009 by Bernhard Stahl. Published by the American Institute of Aeronautics and Astronautics, Inc.

Pott-Pollenske M.,German Aerospace Center | Pott-Pollenske M.,Institute of Aerodynamic and Flow Technology | Wild J.,German Aerospace Center | Wild J.,Institute of Aerodynamic and Flow Technology | And 2 more authors.
20th AIAA/CEAS Aeroacoustics Conference | Year: 2014

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.

Gulhan A.,German Aerospace Center | Gulhan A.,Institute of Aerodynamic and Flow Technology | Siebe F.,German Aerospace Center | Siebe F.,Institute of Aerodynamic and Flow Technology | And 8 more authors.
Journal of Spacecraft and Rockets | Year: 2014

The Sharp Edge Flight Experiment II was launched from the Andoya rocket range in Norway on 22 June 2012, consisting of an extensively instrumented scientific payload on top of a two stage rocket configuration. With an apogee of about 177 km, the vehicle achieved flight velocities up to 2790 m/s corresponding to Machnumbers up to 9.3. More than 96% of the pressure sensors provided excellent data during the ascent and descent phases. Measured pressure data from sensors at different locations of the scientific payload show consistent results concerning the aerodynamic behavior of the vehicle along the complete trajectory. Pressure fluctuations measured during flight show an excellent correlation to angle-of-attack variations. Calculated pressure coefficients from a computational fluid dynamics analysis at selected trajectory points are in good agreement with the measured pressure data.

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