A Novel Test Bed for the Aeroacoustic Investigation of UCAV Configurations with Highly Integrated Propulsion Systems

In this contribution, a novel test bed designed for the experimental investigation of the acoustic signature of unmanned combat air vehicle with highly integrated propulsion systems is presented. The model integrates a curved intake duct design as well as a curved, high aspect ratio, rectangular nozzle design. Operation of the model in suction mode or pressurized mode allow investigations of the intake and nozzle acoustics independently and in a realistic Mach number range, e.g. Ma=0.4 in the intake duct and Ma=0.75 in the jet. Intake sound emissions are found to have a directivity peaking in the forward arc which is strongly dependent on the suction mass flow rate and almost independent of the free-stream Mach number. The jet is found to radiate sound with a rear arc directivity for model scale frequencies above 3.15 kHz. The acoustic is also a strong function of the nozzle mass flow rate only. The overall shape of the jet acoustic directivity suggests the existence of two source component aligned at 90° and 140° to the upstream direction, respectively

KATO-Passagier-Bestandsaufnahme und Arbeitsplanung für 2004

* Beschreibung des Aufbaus von Klimaanlagensystemen moderner Transportflugzeuge. * Identifizierung potentieller Schallerzeuger. * Definition eines Experiments zur Identifikation der Schallentstehungsmechanismen an der Blende bzw. einer Blende in einem turbulenten Nachlauf

Assessment of acoustic quality of differently designed control devices

Novel wing designs will incorporate advanced wing-tip devices for a quick wake-vortex break down and an increased wing performance through different devices, e.g. differential flap setting, airbrakes (vented spoilers), large winglets, mini trailing-edge devices and sub-boundary layer vortex generators. Advanced wing configurations will enhance the aircraft's capability to perform noise abatement flight procedures, but may also generate excess aerodynamic noise. To provide first information on spectral noise characteristics of different devices, noise measurements were performed to check-out the devices' aeroacoustic characteristics. This study was performed in DLR's Aeroacoustic Wind Tunnel (AWB) on a 1/10.6 scaled A340 model wing in high lift configuration. All different devices were tested individually by means of an acoustic mirror. The following major results were obtained: (1) As a means to enhance the decay of wake vortices but avoid excess aerodynamic noise generation, DFS (except for the 0°/32° configuration) is superior over different spoiler settings or any of the tested individual wake vortex devices. (2) Noise from mini TEDs gain importance for deflection angles above 60°. (3) Even small spoiler deflections cause significant excess noise generation. (4) SBVGs were found to be essentially uncritical with respect to excess aerodynamic noise generation

Installation Effects of a Propeller Mounted on a Wing with Coanda Flap. Part II: Numerical Investigation and Experimental Validation

Within the framework of the German project B�ürgernahes Flugzeug" (Citizen Friendly Aircraft), we are investigating the effect of installation on propeller sound. A nine-bladed propeller installed in front of a wing equipped with a Coanda flap is considered. This configuration produces significant high lift and thereby considerably influences the inflow condition of the propeller. The sound generated by the propeller is furthermore shielded by and reflected off the wing. In this contribution, we present an implementation of an acoustic propeller model in a �finite differences CAA (computational aeroacoustics) code. Comparisons of isolated propeller computations in a quiescent flow with an analytical model illustrate the correct numerical implementation. The verification of the implementation is presented for an example of an isolated propeller. A comparison for the installed propeller with experiments is conducted for different settings

Effect of Slat Gap on Farfield Radiated Noise and Correlation with Local Flow Characteristics

Significant source noise reduction efforts are needed to cope with the "Visions 2020" of the "group of personalities" in Europe. This vision defines an aircraft noise reduction goal of 15 dB per operation until 2020, which inherently requires a reduction of airframe noise, and thus of high lift devices noise, by this same amount during landing approach. Since high lift devices noise is known to be dominant by slat noise, the aerodynamic optimization of slat-wing configurations must also account for noise aspects. Therefore the effect of slat gap variations on slat noise generation was investigated through a scale model high lift devices experimental wind tunnel study. In parallel CFD calculations (2D RANS) were performed for all test configurations to correlate measured slat noise characteristics with flow field data. Broadband slat noise levels were found to scale best with the local flow velocity at the pressure (cove) side close to the upper slat trailing-edge. Relative to the reference slat gap width a broadband noise reduction of up to 10 dB was achieved for reduced gap width (up to 15%), accompanied by an up to 4% degradation in maximum lift. For high angles-of-attack slat noise spectra were governed by a complex tone pattern, which do not follow a simple harmonic scheme but approximately scale with inflow velocity

Landing gears aerodynamic interaction noise

Airframe noise is generated as a result of the interaction of turbulent flow with different airframe components, i.e. the high lift devices and landing gears in particular, and may dominate over engine noise in the approach phase of large commercial aircraft. This paper describes the landing gears interaction noise research work in the EC co-financed project "Significantly Lower Community Exposure to Aircraft Noise" (SILENCER). Systematic steady and unsteady landing gear wake measurements were performed on differently scaled A340 type centre and main landing gears. The analysis of wake measurements showed almost isotropic turbulence characteristics for short distances downstream. Noise measurements were performed for a main landing gear being exposed to the wake flow of a centre landing gear. It turned out that only low frequency interaction noise is likely to be radiated while at high frequencies a noise reduction is obtained due to reduced mean wake flow speed

Lärmmessung an einer MD-11 zur Ermittlung lärmminimaler Landeverfahren

Im Auftrag der Deutschen Lufthansa AG wurden im Rahmen des Projekts "Leises Flugzeug" Überflugmessungen an einem Frachtflugzeug vom Typ MD-11F (Boeing) durchgeführt. Neben der Lärmabstrahlung beim Start interessierte vor allem das Potential der Lärmminderung beim Landeanflug, durch unterschiedliche Stellungen der Landeanflug, durch unterschiedliche Stellungen der Landeklappen (flaps) sowie bei unterschiedlichen Drehzahlen (Leistungen) der Tragflächen-Triebwerke im Vergleich zu der des Hecktriebwerks. Für eine statisch abgesicherte Datenanalyse waren aus den durchgeführten Landeanflügen zu wenige auswertbare Messdaten verfügbar. Die Ergebnisse sind daher eher im Sinne eines zu erwartenden Trends zu interpretieren