PRODUCTS & SERVICES
AEROSPACETESTINGINTERNATIONAL.COM // DECEMBER 2019 75
efficient wind
tunnel testing
Gaining more insights into aeroacoustic
performance and increasing productivity
with dedicated wind tunnel testing solutions
Trends in aviation involve a continuous
pressure to increase performance, all the
while reducing pollutant and
environmental noise emission. And even with
the industry’s recent efforts in aircraft noise
reduction, airframe noise generated by
landing gear, flaps, slats or other high-lift
devices are still significant contributors to
aircraft acoustic emissions, especially during
approach and landing.
Wind tunnel tests help investigate new
aircraft concepts, verify performance of
innovative designs, and validate prediction
models. Thanks to increasing computational
power, more models are used in design
phases, and wind tunnel testing is the
ultimate way to validate these models long
before the aircraft can actually fly. However,
wind tunnel testing typically involves high
costs linked to the preparation of the test
item and operation of the wind tunnel and
must be performed efficiently to get the most
out of the limited testing time.
Siemens, in cooperation with its partner
MicrodB, has developed a highly efficient
solution for aeroacoustic wind tunnel testing.
This solution allows detailed and accurate
aeroacoustic measurements through its data
acquisition system, the latest processing
algorithms and customized acoustic array
techniques. Measurements are best done in
an integrated platform, where
multi-physics testing, both for
aerodynamics and aeroacoustics
are conducted to gain the most
insights possible into aircraft
performance, and especially into noise
generation mechanisms. Moreover, the
productivity of the tests is of utmost
importance and fast processing techniques
are essential. Through smart data
management and run comparison, many
aircraft configurations can be tested and
evaluated in a minimum time.
This is nicely illustrated in a measurement
campaign performed at the RUAG LWTE
(Large Wind Tunnel Emmen). An acoustic
array with flush-mounted microphones was
placed on the wind tunnel floor, about 2.4m
from the aircraft model. This technique allows
for a view of the source mechanisms to be
obtained without perturbing the flow or the
acoustic field of the source location. The
Simcenter SCADAS high-speed data
acquisition system acquired the pressure
signals from the array microphones and
pressure signals from kulite sensors mounted
on the aircraft model to monitor aerodynamic
performance. Simcenter Testlab software
acquired aircraft position, aerodynamic data
and acoustic data in a unified platform and
with high synchronization accuracy.
A processing technique is used to analyze
time delays between each microphone signal
and reconstruct an acoustic source map of
the aircraft for selected frequencies. With
enhanced GPU-accelerated computing, the
team obtained the detailed sound source
localization results just a few minutes after
the measurement, which allowed them to
adjust the test plan on-the-spot and test the
most relevant configurations. The source
localization map provides a detailed aircraft
image with the noise sources colored
according to relative intensity.
This dedicated testing solution developed
by Siemens combines the essential elements
to provide higher efficiency and deeper
insights for wind tunnel testing. As testified
by the airframe noise senior engineer in
charge of this test campaign, “The sound
source localization technique developed by
the Siemens and MicrodB team, together with
the acoustic array provided by RUAG Aviation,
proved to be very accurate. It allowed us to
clearly identify complex aeroacoustic source
generation mechanisms. These
measurements provide essential engineering
insight in the development of quieter and
more efficient aircraft.” \\
1 // Aircraft model inside
the RUAG wind tunnel
with the acoustic array on
the floor
2 // Sound source
localization results at
5kHz for the aircraft model
with and without landing
gear (Images courtesy of
RUAG Aviation)
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