Hv. Fuchs et D. Eckoldt, U-BEND SILENCERS FOR AN AEROACOUSTIC WIND -TUNNEL, Zeitschrift fur Flugwissenschaften und Weltraumforschung, 20(6), 1996, pp. 248-256
The paper describes construction measures for the acoustic improvement
of an aero-acoustic wind tunnel which mainly serves for the testing o
f road vehicles. The solution introduced consists of membrane absorber
baffles installed in the ducts on both sides of the fan thus providin
g sufficient damping at low frequencies and of bending vanes profiled
with porous Polyester foam covered by a thin coating which are placed
in each of the four corners in order to attenuate medium and high freq
uencies of the noise emitted into the measuring hall. Moreover, for ab
sorption purposes, the measuring hall was lined with a novel type of b
roadband absorbers consisting of Polyester foam plates mounted in fron
t of membrane absorbers. The solution applied in the flow duct takes a
dvantage of the specific virtues of membrane absorbers, i.e. their sle
nder construction with a total thickness of only 212 mm as well as the
ir smooth surfaces. In the wind tunnel both these advantages yield an
only slight loss in the maximum flow velocity achievable. The paper de
als with the aeroacoustic improvement of a wind tunnel which is not on
ly of use in the automotive industry but just as well in aircraft rese
arch. The aeroacoustic performance of wind tunnels plays an important
role e.g. when the how noise of aircrafts is being tested. The methods
and materials presented herein may therefore recommend themselves as
retrofit measures applicable to many existing wind tunnels.