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CONGRATULATIONS,
with STAR-CD you have chosen the best software for
Aeroacoustics source predictions, with proven efficiency
of transient solution, accuracy of discretization
and advanced turbulence modeling, fit for purpose.
It has been validated against experimental data,
integrated within a process tool-kit for acoustics
analysis, and is now beginning to be used widely
among STAR-CD users.
At the start of this year, recognition
of the need for industrial tools to predict flow noise
led to the formation of a CD-adapcoindustry sponsored
strategic partnership. The project, named DESTINY-AAC
(Detached Eddy Simulation for the Transportation INdustrY – AeroACoustics),
targets ambitious but realizable goals. These are the
provision of robust LES-type turbulence and advanced
near-wall modeling, and their validation against a
wide variety of aeroacoustics examples, which are currently
a high priority in the transport sector. This includes
noise from HVAC systems and air delivery, external
flow including A-pillar and wing-mirrors, fans, cavities,
pantographs and high-speed elevators.
Complementary to the provision of
advanced turbulence modeling, noise propagation to
the near and far field is realized through coupling
to new aeroacoustics features in LMS International’s
software SYSNOISE, which imports STAR-CD transient
data and compiles equivalent sources.
DESTINY-AAC has completed the first
of two stages. The implementation and functional testing
of Detached Eddy Simulation (DES) [1] and hybrid-wall
functions are finished. The project now enters its
testing phase, performed by Air International, Audi,
BEHR, Bombardier, DaimlerChrysler, Denso and Sulzer
Innotec on core industrial applications.
Preliminary results have confirmed
expectations that the advanced models are robust, efficient
and strongly suited to aeroacoustics. The DES implementation
in STAR-CD is valid for the k-e, k-w and Spalart-Allmaras
turbulence models and their variants. These RANS models
in unsteady mode are active in the near-wall region
and transition smoothly to a Smagorinsky-like sub-grid
scale model away from surfaces. The hybrid wall-function,
which is valid for the full low and high-Reynolds number
y+ range, relaxes the tedious necessity for the user
to produce appropriate near-wall mesh spacing.
Applied to high-speed cavity acoustics,
these new DES modeling techniques demonstrate real
benefits compared with traditional unsteady RANS or
LES turbulence modeling. RANS modeling, due to over-prediction
of eddy-viscosity underestimates the broadband noise
content or incorrectly predicts narrowband modes. LES,
in contrast, greatly improves the broadband prediction,
but requires very fine near wall resolution or else
the low-frequency noise content is over predicted.
For further details, please contact: fred@cd.co.uk
[1] Spalart, P.R., Jou, W.H., Strelets,
M. and Allmaras, S.R., "Comments on the Feasibility
of LES for Wings, and on a Hybrid RANS/LES Approach,",
First AFOSR International Conference on DNA/LES, Ruston,
Louisiana, USA. 1997
[2] Henshaw M.J de C., "M219
Cavity case in Verification and Validation Data for
Computational Unsteady Aerodynamics", RTO-TR-26,
AC/323(AVT)TP/19, October 2000
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A2 side-view
mirror, courtesy of Audi AG
HVAC box and flap,
courtesy of BEHR
HVAC blower
y+ distribution,
courtesy of Denso Thermal Systems
PSD at a point along the cavity
ceiling - DES compared with unsteady RANS and LES for high speed cavity
acoustics. Data [2] from QinetiQ
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