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The fuselage surface pressure fluctuations on an Airbus-A320 aircraft at cruise conditions are simulated by solving a Poisson equation. The right-hand-side source terms of the Poisson equation, including both the mean-shear term and the turbulence-turbulence term, are realized with synthetic anisotropic turbulence generated by the Fast Random Particle-Mesh Method. The stochastic realization is based on time-averaged turbulence statistics derived from a RANS simulation under the same condition as in the flight tests, conducted with DLR's Airbus-A320 research aircraft. The fuselage surface pressure fluctuations are calculated at three streamwise positions from front to rear corresponding to the measurement positions in the flight tests. One- and two-point spectral features of the pressure fluctuations relevant to the fuselage surface excitation are obtained and analysed.

The contribution provides an overview on accomplished wind tunnel testing and simulation activity within the German national wind energy project BELARWEA. The project aimed at numerical tool development and validation to support the design of both aerodynamically efficient and low-noise wind turbine rotors. The focus was set on the tip region, herein defined as the outer 20 % of the rotor radius, i.e. addressing noise generation from the trailing-edge- and tip vortex regions. Aeroacoustically driven 2D profile design, 3D winglet design and 2D/3D CFD/CAA analysis were supplemented by the transfer of passive noise reduction technologies from aerospace applications to wind turbine blades. Validation experiments were performed in systematic evaluation steps, namely - at 2D blade sections in the Acoustic Wind-Tunnel Braunschweig (AWB) of DLR, and - at 3D blade tip models in the larger acoustic facility DNW-NWB, operated by the German-Dutch Wind Tunnels foundation. A noise reduction potential of up to 8 dB could be demonstrated in the NWB experiment, confirming the previously documented AWB results. The overall reduction was composed of a 2-4 dB reduction by a new low-noise profile design RoH-W-18%c37 (relative to a NACA 64-618 reference configuration) and an additional ~4-6-dB reduction by brush add-ons.

Das Projekt BELARWEA "Blattspitzen für Effiziente und LärmArme Rotoren von WindenergieAnlagen" widmet sich der Weiterentwicklung und Validierung von numerischen Schallvorhersagenmethoden für Windenergierotoren, um zukünftig den rechnergestützten Entwurf von gleichzeitig effizienten und geräuscharmen Rotorblättern zu ermöglichen. Der Projektfokus lag auf der Blattspitzenregion (äußere 20% des Rotorradius), die aufgrund der dort höchsten Relativgeschwindigkeiten am Rotor für die Schallerzeugung entscheidend ist.

In the context of aircraft cabin interior noise, the fuselage structural excitation by turbulent boundary- layer (TBL) flows is an important noise source for aircraft manufacturers to deal with. Aircraft at cruise conditions are flying at high Mach numbers, typically between Ma = 0.78...0.85, dependent on the type and mission of the aircraft. At these flight conditions, the TBL around the fuselage is turbulent and features regions with high turbulence intensity. The vortices within the TBL cause pressure fluctuations on the fuselage and therefore, its structure receives energy and starts to vibrate. This vibration is inter alia dependent on the flow velocity and thus, the strength of the TBL. Due to advanced low-noise engine technologies the TBL remains the dominating source of cabin noise at current state-of-the-art aircraft. Therefore, Airbus has launched dedicated research efforts to characterize the TBL as a source of cabin acoustics and to predict the induced structural excitation of any fuselage section. Especially in an early design stage sufficiently precise noise level estimates are important to evaluate/optimize design variants (e.g. different aircraft shapes) from an acoustical viewpoint. Today's semi-empirical models to predict the TBL-induced pressure fluctuations have been mainly developed on the basis of wind-tunnel tests on flat plates. Correspondingly, these commonly applied predictions are not applicable in areas subjected to disturbed flows (i.e. at the junction between the wing and fuselage, the cockpit or tail regions). A universal prediction approach requires more detailed model descriptions of the TBL strength and spatiotemporal development as characterized by the surface pressure auto-spectrum and wavenumber-frequency spectrum, respectively. In this paper an approach is presented to bridge the gap between simple flat plate estimates and higher fidelity predictions based on computational fluid dynamics (CFD) and computational aeroacoustics (CAA). As the result of an in-depth literature review on available auto-spectrum models the semi-empirical GOODY model was selected and extended to cover arbitrary regions of the fuselage. In the new approach aerodynamic parameters are directly taken from CFD calculations. Besides, the turbulence kinetic energy (TKE) was identified as major driving quantity and was therefore, included in the new model. This new model was derived and verified using measured auto-spectra from flight tests, performed on the Advanced Technology Research Aircraft (ATRA) of the German Aerospace Center (DLR), an Airbus A320. It is therefore valid in a large parameter space, covering the operational range of a short- to medium-haul aircraft. In parallel, a fully numerical procedure is proposed to predict the auto-spectrum as well as the wavenumber-frequency spectrum by making use of the Fast Random Particle-Mesh Method (FRPM) of the DLR. In selected areas the FRPM approach provides both auto-spectra and wavenumber-frequency spectra with high prediction quality. Currently, the method is limited to frequencies below or equal 2500 Hz. Beside these source modeling activities, rhombic and elliptical wavenumber-frequency models from literature are reviewed and the effect on a flat plate vibrational response is described. This study is conducted by using GRAHAM's method implemented in Matlab and by a commercial implementation in an Statistical Energy Analysis (SEA) software package. Both approaches show equal results for the flat plate test. Finally, the developed auto-spectrum model, the different reviewed wavenumber spectrum models, the FRPM-based predictions and a wavenumber spectrum model fitted to ATRA flight test data are used as variable inputs for an SEA at the real aircraft. For the SEA computations the commercial software VA One is employed with Airbus A320 SEA models used for research and development at Airbus. Structural vibration data, estimated with these models are finally compared with measured structural vibrations from flight tests in different areas of the aircraft. Estimated structural vibrations give an overall good collapse with the measured accelerations. However, detailed parametrical comparisons indicate the individual weaknesses of different wavenumber-frequency models in distinct frequency ranges. Especially in the low frequency range semi-empirical models tend to deviate from measurements.

Klimaanlagensysteme stellen eine wesentliche Lärmquelle in der Kabine heutiger Verkehrsflugzeuge dar. Um eine gleichmäßige Belüftung des Passagierraums zu gewährleisten, werden innerhalb des Rohrsystems Drosseln in Form von Blenden eingesetzt. Hinsichtlich der Schallentstehung in Klimarohrsystemen sind derartige Blenden von besonderer Bedeutung und ein Auslegungskriterium