DAGA 2010 - Deutsche Gesellschaft für Akustik eV

Programm DAGA 2010 81
along a spatially developing flow profile. Thus the sound field changes
gradually with the flow profile. Its modal decomposition along the extend
of the duct on an assumed radial constant flow profile allow conclusions
about the influence of the radial non constant flow profile on the spatial
changes of the radial structure of the sound field.
Di. 16:10 Grashof C 116 Modelle u. Methoden Aeroakustik I
Accurate Coupling Information for Hybrid CAA-Methodologies Based
on Compressible Flow Simulations.
W. de Roeck und W. Desmet
KU Leuven, Dept. Mechanical Engineering
Hybrid CAA methodologies, based on domain decomposition, are commonly
considered as the most appropriate technique for the numerical
simulation of aerodynamically generated noise and their far-field propagation
with a reasonable computational effort. A crucial step, largely
determining the accuracy of the final acoustic results, is the coupling
between the aerodynamic source region and the acoustic propagation
region. It is known that the spatial and temporal truncation of the
source domain simulation together with the interpolation from the ’fine’
source domain mesh to the ’coarse’ acoustic grid strongly influence the
aeroacoustic radiation. When using a compressible flow simulation, the
acoustic fluctuations, which are inherently present in the source domain
results, can introduce an additional source of errors in the aeroacoustic
radiation predictions. In this case, an aerodynamic/acoustic splitting
technique, which allows separating the aerodynamic and acoustic fluctuations
from the source domain simulation, can largely improve the accuracy
of the aeroacoustic prediction. This paper illustrates the benefits
of using this aerodynamic/acoustic splitting technique for a number of
commonly used CAA benchmark problems. It is shown that the final accuracy
of hybrid CAA methodologies can be largely improved, with only
a minimum of additional computational effort, by extracting accurate
coupling information from the source domain results.
Di. 16:35 Grashof C 116 Modelle u. Methoden Aeroakustik I
Introducing Lined-wall Boundary Conditions in the DLR Timedomain
CAA Solver PIANO
A. Bassetti a , S. Guerin a und O. Kornow b
a Deutsches Zentrum für Luft- und Raumfahrt (DLR), Berlin; b Deutsches
Zentrum für Luft- und Raumfahrt (DLR), Braunschweig
Understanding the physical mechanisms that occur in the aeroacoustics
of lined surfaces is a key issue for the optimal design of passive sound
absorbers (liners) in aircraft engines. The liners play an important role to
reduce the noise emitted by modern transport-aircraft engines. Engine
and engine-nacelle manufacturers base their designs on gathered past
experience and, more recently, on computational aeroacoustics (CAA)
solutions, including impedance-type boundary conditions to simulate the