Aircraft noise generation and assessment

Aeroacoustic wind tunnel design
  • J. Pereira GomesEmail author
  • A. Bergmann
  • H. Holthusen
Original Paper


Further progress in airframe noise research including noise prediction and noise reduction solutions depends on the availability of aeroacoustic wind tunnel test facilities with superior aerodynamic and acoustic quality. The demand for aeroacoustic wind tunnels with extremely low background noise and pressure fluctuations, yet with a relevant test section cross-section area and flow velocity, increased significantly over the last decade. In the future, this demand will continue to grow to cope with the challenging noise reduction objectives for aviation noise defined for the years to come. The present text is focused on the state-of-the-art aeroacoustic wind tunnels available today and their design. The design guidelines discussed here assume a classic aerodynamic wind tunnel as a baseline. Therefore, the present text is addressed to both those who are interested in the design of a completely new aeroacoustic wind tunnel as well as those interested in the acoustic upgrade of an existing aerodynamic wind tunnel. As a direct consequence of the multi-disciplinary nature of this complex task, and the multitude of solutions and design tools that are required to complete it, the approach followed here subdivides the design of the aeroacoustic wind tunnel into four main sections: wind tunnel airline circuit (includes the first and second airline cross legs), drive unit and anechoic plenum. While the design approach for the airline circuit and the drive unit is strongly based on coupled numerical solutions of CFD and acoustic solvers, the design of the acoustic plenum gives more emphasis to in situ observations and to experimental results. The main sections of the aeroacoustic wind tunnel and their best design are discussed separately in this contribution.


Aeroacoustic Aerodynamic Wind tunnel Acoustics 

List of symbols


Area, m\(^2\)


Reference area (\(= 1~\hbox {m}^2\)), m\(^2\)

\(A_{\text {p}}\)

Wall partition area, m\(^2\)


Speed of sound, m/s

\({C_{{\text {p}},_{{\text {RMS}}}}}\)

Pulsating coefficient


Duct diameter, m


Frequency, Hz


Brightness per histogram level


Ratio of specific heats


Length, m


Duct length, m

\(l_{{\text {ef}}}\)

Effective duct length, m

\(L_{\text {m}}\)

Overall brightness level


Sound pressure level

\({L_{{\text {p}},_{{\text {OSPL}}}}}\)

Overall sound pressure level

\(\varDelta f\)

Frequency bandwidth, Hz

\(\varDelta L_{\text {p}}\)

Acoustic damping

\(\varDelta p_{{\text {loss}}}\)

Pressure loss


Wavelength, m


Mass flow rate, kg/s


Mach number


Pressure, N/m\(^2\)


Reference pressure (\(= 20~\mu\)Pa), N/m\(^2\)

\(p_{{\text {tot}}}\)

Total pressure, N/m\(^2\)


Distance, m


Offset of the acoustic centre along the measurement path, m

\(R'_{\text {I}}\)

Apparent intensity sound reduction index


Flow density, kg/m\(^3\)


Flow velocity, m/s


Volume, m\(^3\)



Active resonance control




Broadband noise


Blade passing frequency


Computational fluid dynamics


German Aerospace Centre


German–Dutch Wind Tunnels foundation of DLR and NLR






Large low-speed facility


Netherlands Aerospace Centre


Low speed wind tunnel Braunschweig


Overall sound pressure level




Sound pressure level




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Copyright information

© Deutsches Zentrum für Luft- und Raumfahrt e.V. 2019

Authors and Affiliations

  1. 1.German-Dutch Wind Tunnels (DNW)BraunschweigGermany
  2. 2.German-Dutch Wind Tunnels (DNW)MarknesseThe Netherlands

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