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Michel U.,CFD Software Entwicklungs und Forschungsgesellschaft mbH
21st AIAA/CEAS Aeroacoustics Conference | Year: 2015

The flight effect on jet mixing noise cannot be determined correctly in open jet wind tunnels by using the industry standard correction method for the shear layer influence. One important consequence is that the forward arc amplification of jet noise observed in many flyover tests cannot be replicated in free-jet windtunnel tests. The reason proposed in this paper is a coherence loss in the radiated sound field due to scattering in the tunnel shear layer. This effect is unimportant for point sources but becomes important for distributed and partly coherent sources like jet noise. The effect is proportional to the tunnel Mach number, to the ratio between thickness of the tunnel shear layer and the jet diameter, and to the ratio between the propagation distance outside the shear layer to the wave-normal distance of the microphone. As a consequence of the loss of coherence the sound-pressure levels measured outside the tunnel are too low and the resulting relative velocity exponents too large. The effect depends on the geometric conditions which differ between the various tunnels. © 2015, American Institute of Aeronautics and Astronautics Inc, AIAA. All Rights Reserved. Source

Wang L.,TU Berlin | Mockett C.,TU Berlin | Knacke T.,TU Berlin | Thiele F.,CFD Software Entwicklungs und Forschungsgesellschaft mbH
Notes on Numerical Fluid Mechanics and Multidisciplinary Design | Year: 2012

Detached-Eddy Simulation (DES) is a promising method for efficient simulation of broadband noise at minimal computational cost. Here, results from a study of broadband noise simulation using state-of-the-art DES methods are presented for a rudimentary landing gear configuration. The DDES and IDDES variants are compared with experiments in incompressible simulations. IDDES shows mild improvement in agreement and some increase in the resolution of high frequencies. An attempt is made to independently verify published results for far-field sound prediction, using a compressible simulation coupled with Ffowcs-Williams/Hawkings (FWH) integration. In contrast to the published results, our results do not provide evidence of unexpectedly strong roles played by the ceiling or by quadrupoles. Our results furthermore predict much lower far-field noise levels than the published results. Good agreement between solid and permeable FWH surfaces is found as long as the permeable surfaces are open downstream. © 2012 Springer-Verlag Berlin Heidelberg. Source

Agency: Cordis | Branch: FP7 | Program: JTI-CS | Phase: JTI-CS-2010-4-GRC-02-006 | Award Amount: 147.28K | Year: 2011

Reduction of aerodynamic drag is central to the ACARE 2020 goal of reducing fuel consumption in air transportation. For rotorcraft, the majority of the drag occurs due to extensive flow separation around the fuselage and rotor hub. Such highly unsteady flows present significant challenges for computational fluid dynamics (CFD) techniques in terms of solution fidelity and computational expense. However, a new family of hybrid RANS/LES techniques addresses this conflict by mixing pure modelling (RANS) and partial resolution (LES) of the turbulent motion to provide an optimal tradeoff between solution fidelity and computational cost. Of these, the well-established detached-eddy simulation (DES) method has been selected for the HELIDES simulations due to its high maturity and inherent suitability. Through participation in numerous EU projects (e.g. FLOMANIA, DESider, ATAAC), the consortium has developed a very high level of expertise with the development and application of these methods, including to helicopter fuselage simulation. The HELIDES consortium has furthermore played a central role in the implementation and validation of cutting-edge DES methods in an efficient, incompressible, unstructured CFD solver that can capture complex geometries with rotating components. Furthermore, novel analysis techniques for the quantification of the random error in statistical quantities provides a pragmatic means to manage the significant problem of finite simulated time samples. With these well-suited tools and expertise, together with access to very large computing resources, the HELIDES consortium considers itself ideally equipped to perform the demanding high-fidelity simulations specified by the Call.

Wang L.,Tsinghua University | Mockett C.,CFD Software Entwicklungs und Forschungsgesellschaft mbH | Knacke T.,TU Berlin | Thiele F.,CFD Software Entwicklungs und Forschungsgesellschaft mbH
19th AIAA/CEAS Aeroacoustics Conference | Year: 2013

In the present paper, compressible IDDES at Mach numbers of 0.115 and 0.23, coupled with FWH integration, were carried out for a rudimentary landing gear configuration. The obtained Mach number scaling of around M6.4 confirms the expectation that the contribution of dipoles is dominant. Comparison with experimental far-field sound measurements has also been made. Both the permeable-surface and the solid-surface compressible results agree well with the experimental data to within 2 dB. Incompressible calculations are often applied to complex industrial configurations in the low-Mach regime. To assess the validity of this practice, incompressible calculations were also conducted. Provided that wave reflections were taken into account in the far-field integration, the incompressible results agreed well with the compressible case, being at most 2 dB quieter. Modest savings in computational resources were achieved, which could have been higher with an adjusted grid. However, the applicability of such incompressible calculations is expected to be strongly case-dependent. Source

Agency: Cordis | Branch: H2020 | Program: RIA | Phase: MG-1.10-2015 | Award Amount: 1.80M | Year: 2016

The proposed project, IMAGE, is relevant to Topic MG-1.10-2015, aiming to enhance the EU-China collaborative effort focusing on Innovative methods and numerical technologies for airframe and engine noise reduction. The project consortium consists of 12 partners. The purpose of IMAGE is to investigate experimentally and numerically innovative airframe and engine noise-reduction technologies and, in a systematic conjunction, to develop robust methodologies of addressing these technologies. Airframe noise is addressed by tackling landing gears and high-lift devices, and engine noise through its fan component. Fundamental investigations of three key control strategies are carried out: plasma actuation, turbulence screens and innovative porous materials, on a platform of three configurations, relevant to airframe and aero-engine noise generation and control, including a wing mock-up, tandem cylinder and engine-fan duct. Beyond this, IMAGE explores further the installation effect of aeroacoustic engine-jet/wing interaction with a simplified configuration, as well as low-noise concepts and optimal noise-actuation methods by means of aeroacoustic optimization. The project will conclude a comprehensive understanding of the physical mechanisms concerning flow-induced airframe and engine-fan noise generation, propagation and control, and of further improvement of beam-forming technology and noise source identification in aero-acoustic experimental analysis. The experiment will generate well-documented database, supporting the development of numerical modelling and simulation methodologies for reliable validation and verification. To this end, with technical synthesis and industrial assessment, the noise control methods will be optimized and be facilitated towards potential industrial use, and the methodologies developed should form a robust part of advanced tools in industrial practice.

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