2.5 Constraints of Testing in a Wind Tunnel
41
Fig. 2.10 Magnetic levitation of a model in the R2Ch wind tunnel of the ONERA Meudon centre
(1965) (© ONERA)
regime as the transition modes are not influenced by the freestream turbulence, but
could be affected by different noise sources from the engine for instance. This issue
is more severe during transonic and supersonic tests. In an attempt to remedy these
problems, “quiet” wind tunnels have been developed where special precautions are
taken to attenuate the noise and disturbances caused by the installation (see Sect. 5.4).
The noise produced by the flow over a vehicle is an inconvenience for both the
passengers and the surrounding environment and is therefore the major concern in
the field of aeroacoustic. In order to study the sources of noise it is necessary to take
special measures during the design of the test section, as well as the return circuit, as
the acoustic waves emitted at the level of the model are reflected by the solid walls.
The motor and fan or compressors also produces parasitic noise, often very high
in amplitude. Wind tunnels intended for aerodynamic noise studies must therefore
be subjected to specific acoustic treatment and are normally equipped with noise
absorbing or attenuation systems (see Sect. 3.2).
41
Fig. 2.10 Magnetic levitation of a model in the R2Ch wind tunnel of the ONERA Meudon centre
(1965) (© ONERA)
regime as the transition modes are not influenced by the freestream turbulence, but
could be affected by different noise sources from the engine for instance. This issue
is more severe during transonic and supersonic tests. In an attempt to remedy these
problems, “quiet” wind tunnels have been developed where special precautions are
taken to attenuate the noise and disturbances caused by the installation (see Sect. 5.4).
The noise produced by the flow over a vehicle is an inconvenience for both the
passengers and the surrounding environment and is therefore the major concern in
the field of aeroacoustic. In order to study the sources of noise it is necessary to take
special measures during the design of the test section, as well as the return circuit, as
the acoustic waves emitted at the level of the model are reflected by the solid walls.
The motor and fan or compressors also produces parasitic noise, often very high
in amplitude. Wind tunnels intended for aerodynamic noise studies must therefore
be subjected to specific acoustic treatment and are normally equipped with noise
absorbing or attenuation systems (see Sect. 3.2).