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Application of a discontinuous Galerkin based CAA solver for broadband noise prediction

Liberson, Lev and Lummer, Markus and Mößner, Michael and Ewert, Roland and Delfs, Jan Werner (2018) Application of a discontinuous Galerkin based CAA solver for broadband noise prediction. FAN 2018 - International Conference on Fan Noise, Aerodynamics, Applications and Systems, 18.-20. April 2018, Darmstadt, Deutschland.

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Computational simulation plays a significant role in the development process of modern industrial fans. Computational fluid dynamics (CDF) is widely used for aerodynamic optimization and to gain a fan design with improved efficiency. In addition, the acoustic performance becomes more and more important as it constitutes another unique selling proposition. To obtain a low-noise fan design, efficient computational methods are necessary for the prediction of aerodynamically generated noise. The development of a first principle based broadband fan noise prediction capability is the aim of a cooperation between the industrial partner ebm-papst and the department of technical acoustics of the German Aerospace Center (DLR). A recently developed computational aeroacoustics (CAA) solver DISCO++ is used for broadband noise assessment utilizing stochastically generated sources. The mechanism of noise generation by the flow field of an axial fan is a highly complex three dimensional process. A prominent example is the interaction between blade-tip vortices with the surrounding tip geometry and trailing edge noise from the fan blades. An efficient option for spatial discretization of such highly complex geometric features is provided by unstructured tetrahedral meshes. Such an approach is used in the CAA code DISCO++ to solve the acoustic perturbation equations (APE) with the discontinuous Galerkin (DG) method. To provide a method with comparatively manageable numerical effort a two-step hybrid approach is chosen. In a first step, a Reynolds Averaged Navier Stokes (RANS) simulation is performed to obtain the stationary flow field and statistical turbulence parameters. Thereupon, time-resolved synthetic turbulence is generated by the Fast Random Particle Mesh (FRPM) method on a separate Cartesian grid. From the reconstructed stochastic turbulence an acoustic source term is computed and passed to DISCO++ which in turn computes the sound propagation in the CAA domain. Within this work the results of the DISCO++ simulations of a five bladed ducted axial fan using an acoustic source term based on vorticity structures are presented. The results are compared with measurement and similar computational data. A good agreement over a wide range of frequencies is achieved. It is believed that a vorticity based acoustic source provides the capability to model anisotropic effects of vortex stretching in areas of highly accelerated flows occurring in the tip gap area.

Item URL in elib:https://elib.dlr.de/130274/
Document Type:Conference or Workshop Item (Speech)
Title:Application of a discontinuous Galerkin based CAA solver for broadband noise prediction
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Delfs, Jan WernerUNSPECIFIEDhttps://orcid.org/0000-0001-8893-1747UNSPECIFIED
Date:April 2018
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:No
Keywords:Acoustics, Aeroacoustics, Simulation, Computational Fluid Dynamics, Numerical Aeroacoustics, Synthetic Turbulence, Hybrid CAA Methods, Acoustic Perturbation Equations, Stochastic Turbulence Reconstruction, HVAC Systems, Axial Ventilator, Discontinuous Galerkin Method, Tip Gap Noise
Event Title:FAN 2018 - International Conference on Fan Noise, Aerodynamics, Applications and Systems
Event Location:Darmstadt, Deutschland
Event Type:international Conference
Event Dates:18.-20. April 2018
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 - Simulation and Validation (old)
Location: Braunschweig
Institutes and Institutions:Institute for Aerodynamics and Flow Technology > Technical Acoustics
Deposited By: Liberson, Lev
Deposited On:28 Nov 2019 13:50
Last Modified:28 Nov 2019 13:50

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